NERVOUS SYSTEM [systema nervosum (PNA); systema nervorum (JNA) — one of morfofunktsionalny systems providing regulation of activity of a complete organism.
- 1 History
- 2 A comparative anatomy and ontogenesis
- 3 The physiology
- 4 The role of a nervous system in activity of various bodies and systems
- 5 Biochemistry
- 6 The pathological physiology
- 7 Compensation of the broken functions
- 8 Pathogenetic therapy
- 9 Changes of a nervous system in the course of aging
- 10 Diseases
Even in works of Ancient Greek doctors Gerofil and Erazistrat (Herophiios, Erasistratos) introduced the idea that the page provides to N. sensitive and motive functions of a human body. K. Galen (2 century AD) observed emergence of paralyzes after disturbance of nek-ry parts H. of page. Ancient doctors assumed that functions H. of page are provided with special liquids (humors), to-rye flow on the nerves representing hollow tubes to various bodies. Only in Renaissance together with resuming of interest in natural sciences in general functions H. of page became a subject of scientific research. The important role was played by promotion in 1649 by the fr. philosopher and the scientist R. Descartes of the principle of reflective (reflex) activity of N. of page. The term «reflex» began to be used in the works the English scientist T. Villizy (1672) and the Czech physiologist I. Prokhask (1784).
Direct neurophysiological researches began to be conducted at the beginning of 19 century (see. Neurophysiology ). By this time the base unit of N. of page was already open — nervous cell (see), studying of the course of nerve fibrils is begun, the first scientific data on the nature of nervous processes appeared. After opening in 1791 of «animal electricity» it became clear to L. Galjvani that electric processes are closely connected with nervous activity. At the end of 18 — the beginning of 19 century participation of a spinal cord in implementation of motor reflex reactions, and a myelencephalon — in maintenance of respiratory movements is proved to Oylo. An important role Ch. Bella and F. Marangdi played works, to-rye showed that function of back and ventral roots of a spinal cord is various and that back roots are related to sensitivity, and lobbies — to the movements. Works Ch. Bella and F. Marangdi were an incitement for rapid development of researches on localization of functions in N. of page.
Opening in 1863 by I. M. Sechenov was of great importance for further development of physiology of N. of page along with excitement (see) the second the basic nervous process — braking (see). I. M. Sechenov's idea that interaction of processes of excitement and braking is a basis of any kind of reflex activity completely was confirmed by all further course of researches of physiology of N. of page.
In the second half of 19 century works of histologists found in detail out structure of nervous cells, the course of pix of shoots, features of bonds between them. The truth * in the main views of the principles of a structure of N. of page neurohistologists were divided into two opposite camps. According to one point of view, a cut R. Kelliker, V. Valdeyer and S. Ramone-and-Kakhal were supporters, nervous cells only contact to shoots with each other, but anywhere do not merge together. C. Golgi, I. Apati, A. Bete considering N. page as continuous network, in a cut shoots of one cell and the fibrilla which is contained in them adhered to the opposite point of view, without being interrupted, pass in following, forming a hook naz. neyropil. Only after introduction to practice morfol, researches of the supermicroscope having sufficient resolving power for exact definition of ultrastructure of field of connection of two nervous cells, the dispute was finally resolved in favor of the first point of view (see. Neural theory ).
Achievements in area of identification of the basic nervous processes, and also researches of the main features of morphology of N. of page allowed to begin active studying of functions of a spinal cord (Ch. Cher-rittona works, H. E. Vvedensky, R. Magnus) and trunk of a brain (F. V. Ovsyannikov, N. A. Mislavsky, L. Luchani's work, etc.).
In the book «Reflexes of a Brain» (1863) I. M. Sechenov proved the provision that the highest departments of c. items of page also function by the principle of a reflex and can be subjected to an exact research, therefore. The foundation of experimental studying of reflex activity of the highest departments of a brain was laid by I. P. Pavlov, having created a method of uslovnoreflektorny studying of century of N of and on this basis — theory of higher nervous activity (see).
Since the beginning of 20 century active studying of the nature of processes of excitement and braking as bases of reflex activity of a brain (V. Eyntkhoven, A. F. Samoylov, J. Erlanger, G. Gasser, D. S. Vorontsov, I. S. Beritashvili's work) was developed. The total electric fluctuations appearing in various structures of N. of page at rest or at their excitement were subjected to detailed electrophysiologic studying. The method of assignment of electric reactions from separate neurons by means of superthin electrodes was developed (see. Microelectrode method of a research ), detailed data on how process of excitement and braking in various types of nervous cells what intracellular mechanisms of these processes, as transition of activity from one cell on dr\t\tyu etc. is carried out develops are received.
In 20 century researches of mechanisms of coding and processing of information in N. with page, and also development of methods of active intervention in activity of nervous cells by means of various physical and chemical factors were begun.
A comparative anatomy and ontogenesis
It is standard to divide N. of page into the central and peripheral departments. Central department of N. of page, or c. the N of page, combines a head and spinal cord (see. Brain . Spinal cord ), peripheral — all other links of N. of page (see. Peripheral nervous system ). Their communication is carried out through roots spinal and craniocereberal (cranial, T.) nerves. Allocate also the department innervating internals and cardiovascular system. It is autonomous, or autonomic nervous system (see).
A basic element in the organization H. of page — nervous cell (see), characterized by ability to generate excitement (see) in response to irritation (see) and to transfer him to other nervous cells or effector bodies (muscles, glands). Of nervous cells and their shoots (axons and dendrites) there is all N. of page. In it distinguish sensitive nerve terminations, or receptors (see), nervous conductors of excitement (see. Nerves ), kernels (points of processing of information and control centers) representing cellular accumulations, and also neuroplexes and the terminations of motive nerve fibrils in muscles in the form of motor plates. The structural organization H. of page allows to carry out all types of nervous activity (transfer of information, its processing, management, regulation, etc.) by the principle of reflexes.
A comparative anatomy
the First metazoans possessed donervny regulation, at a cut the irritation is transmitted or a humoral way, or through contacts of the next working cells. Coelenterates animals (e.g., hydras) have already diffusion N. of page in the form of the subectodermal neuroplex including the cells disseminated in a wall of an intestinal cavity with their shoots. Total reactions are characteristic of animals with such N. of page, owing to the fact that local excitement extends io to neuroplex evenly in all directions. Further improvement of nervous control is connected with differentiation of nervous elements. One of them kept communication with investments, specializing in perception of irritations (sensory cells), others established connection with motive structures (motive cells). Important point in N.'s development by page is divergent differentiation of primary sensory cells on receptor and basic and trophic (glial).
Emergence of new types of backboneless animals is closely connected with N.'s modification by the village. There was a concentration of nervous cells in certain zones, napr, at polyps, on a circle of an oral disk, and diffusion N. of page changed in ganglionic. Allocate also transitional type H. of page — diffusion and nodal N. to page when the accumulations of nervous cells shipped in depth of tissues of body did not stand apart in nodes yet, and sensitivity of integuments is provided with the diffusion receptor terminations.
Ganglionic N.'s formation by the village was correlated with segmentation of a body of animals. So, annlides in each somite have about 2 nodes connected in a ventral half of a body by posegmentny commissures. Due to longitudinal internodal bonds in a body of a worm chains of nerve knots were created (gangliyev), from to-rykh head (nadglotochny) largest nodes began to play the main role in convergence of nervous signals and increase in volume of processing of various information obtained from the bodies located in the header. This node admits a homolog of a brain of vertebrata.
In nodal N. communication of sensitive and motive neurons is mediated by page through internuncial neurons. To complication of bodies of the head of arthropods there is a further differentiation of head nodes, one of to-rykh (subpharyngeal) becomes control center of front (head) extremities, others (chest) — muscles of back (ambulatory) extremities etc.
At all vertebrate animals the general type of the organization H. of page is sharply other than the organization H. of page of invertebrates and from the earliest stages of embryonic development has no nodal division; The N of page is put in the form of a continuous neurotubule, edge then differentiated on various departments of a brain and is also a source of formation of peripheral nerve knots (in sympathetic and parasympathetic departments of N. of page). The neurotubule is located on back (dorsal) side of a body while nodal N. is located page of invertebrates on the belly (ventral) party. The reason of such sharp distinction in type of the organization H. of page of invertebrates and vertebrata is not clear; apparently, in it the fact that vertebrata came not from elaborate invertebrates of modern type, and from some much more primitive forms which are not possessing in the developed form nodal type H. of page is reflected. At the elementary vertebrata (e.g., at a lancelet) the head end of a brain tube is poorly expressed though subordination in the cranial direction already exists. The further tsefalnzation generates a brain in its initial though not quite issued look (Cyclostoma). At bony fishes the brain is inseparably linked with coordination of movements, with functions of sight and sense of smell. Respectively in it are allocated a rhombencephalon, in Krom kernels of oktavolateralny system (coordination of movements), a mesencephalon with well developed dorsal department (visual functions) and the neoncephalon presented to hl are localized. obr. olfactory shares. A trunk part of a brain since bony fishes actually have no brain raincoat comes to an end with them.
At the amphibians which came out of the water not having noticeable mobility, the cerebellum was not developed, nadsegmentarny management of locomotion concentrated in a setevidny formation of a brainstem. New incentives for progressive development got the mesencephalon connected with function of sight and the neoncephalon continuing to manage behavior of animals. There was a rudiment of a cerebral cortex. Kor-tikolization began to accrue at reptiles though they have a mesencephalon having strong bonds with the subcrustal centers of a neoncephalon kept the dominating positions. The similar direction of development of a brain is traced at the birds possessing an eumorphic cerebellum, thalamic kernels and kernels of the basis of a brain. The main stages of development of a nervous system are shown in fig. 1.
Quickly progressing mammals had new bark, the sizes of hemicerebrums and a raincoat of a brain increased. In process of ascension the relative weight of a brain and the surface of bark increase by the highest steps of an evolutionary ladder. At the person the general surface of bark makes apprx. 84 thousand cm2 (at a chimpanzee apprx. 25 thousand cm2), number of cells of bark more than 10 billion (at a chimpanzee of 1 billion); development of frontal lobes began to prevail (on volume frontal lobes at a chimpanzee nearly 3 times less).
is the Source of education of N. of page at the person the outside germinal leaf producing an ectoderm and neyroepitet y on a dorsal body surface of a germ. Reproduction and consolidation of cells of a neuroepithelium (see) lead to formation of the medullary plate lasting longwise on the back party. Gradually median part of a plate caves in, the fillet which is going deep into a body results.
It matches on time increase of mass of a mesenchyma, derivative of an average germinal leaf, and also with the advent of a back string (chord). Smykaniye of edges of a plate causes transformation of a fillet into a medullary (brain) tube, edges stands apart from an ectoderm and from a mesoderm. From this tube lasting parallel to a chord and dorsalno from it grow medullary combs from the medulloblasts which are differentiated on neuroblasts and spongioblasts to the right and to the left. From neuroblasts various types of nervous cells, and from spongioblasts — cells of a neuroglia (fig. 2) form.
Formation of spinal nodes is connected with a partition of medullary combs on segments. At the same time migration of neuroblasts from a brain tube involves formation two kletochnovoloknisty tyazhy from it on each side — future sympathetic boundary trunks with juxtaspinal segmented nodes. Continuation of migration of neuroblasts is followed by emergence prevertebral, ekstraorganny and intramural nervous gangliyev (see). Shoots of cells of a spinal cord sprout (motor-neurons) in muscles, shoots of cells of sympathetic nodes extend in internals, and shoots of cells of spinal nodes penetrate all fabrics and bodies of the developing germ, providing their afferent innervation (fig. 3).
On other the head end of a brain tube develops. Here the principle of a metamerism is not observed. Expansion of a cavity of a brain tube and increase of mass of cells is followed by formation of primary brain bubbles (fig. 4, a), from to-rykh the brain forms in the subsequent (see). On the 5th week of pre-natal development primary brain bubbles (fig. 4, b) turn into a metencephal (metencephalon) and a myelencephalon (myelencephalon); the front brain bubble in connection with emergence and growth of hemispheres is subdivided into a diencephalon (diencephalon) and an end brain (telencephalon). The end brain in the form of a raincoat surpasses in growth rates at the highest mammals, and especially at the person, all other departments of a brain. Especially violently bark of hemicerebrums develops.
By the time of the birth the volume of a brain of a fruit of the person reaches 375 and the weight of a brain in relation to the weight of all body makes apprx. 10% (the adult has 2,5%). By 10 years of life the volume of a brain of the child reaches 1300 cm3. Final maturing of a brain, as well as all N. the page of the person, nroiskhodit on the basis of work.
the Most universal fiziol, process, on Krom is formed N.'s activity by the village, process of the extending excitement — nervous impulse is (see). The most important property of nervous impulse — ability to a samorasprostra-neniye on a surface of a nervous cell and its shoots. Thanks to this property it performs alarm function and the page is almost only data carrier within N. Nervous impulse can be caused only by change of electric field in a superficial cell membrane towards its decrease (depolarization). Under natural conditions nervous impulses arise or in receptors (see) where the external irritation by means of various mechanisms is always transformed to the electric current flowing through a membrane, or in synoptic connections between nervous cells where such current is created due to action on a membrane of the chemical substances changing its ion permeability (see. Synapse ). Nervous impulses in this cell have the constant amplitude and duration owing to what transfer of any message (information) is possible only by change of the sequence of nervous impulses in time or their distribution between various cells (so-called spatio-temporal coding). The nervous impulses arising in receptor structures go on shoots afferent (i.e. sensitive) nervous cells to c. N of page, bearing information on the irritants operating on receptor structures. Sinaptichesky connections (more precisely, intersynaptic gaps) between the terminations of afferent neurons and the subsequent cells are an obstacle for further distribution of nervous impulse. The same takes place and in synoptic connections of all subsequent cells, and also in connections between efferent (motive) nervous cells and executive bodies (muscles). Therefore in the majority of synoptic connections receipt of nervous impulse in the terminations of presynaptic fiber is followed by allocation these terminations of the chemical transmitter, or a mediator, to-ry diffuses through the synaptic gap dividing cells and interacts with a postsynaptic membrane of the following cell, creating in the last local synoptic processes (see. Mediators ). Such processes are divided into two main types. In one synoptic connections the chemical mediator causes decrease in membrane potential (depolarization of a membrane). The depolarization created by various synoptic terminations in the same cell is summed up and at achievement of a certain critical level is followed by generation of the extending potential, to-ry began to call the exciting postsynaptic potential (EPP); it is expression of local synaptic activation. In other synoptic connections the chemical mediator causes, on the contrary, increase in membrane potential of a postsynaptic cell (hyperpolarization), edges are complicated by emergence of the extending potential and therefore slows down activity of a cell. Such hyperpolarization is designated as the braking postsynaptic potential (TPSP) and is expression of synoptic braking. Interaction of the synoptic exciting and braking processes represents a basis of integrative activity in all departments of c. N of page. Only one type of a mediator can be synthesized and be allocated with a certain nervous cell; depending on the synoptic reaction caused by it nervous cells can be designated as exciting or braking. All primitive afferent and motive nervous cells are exciting. The intra central neurons with short axons though in nek-ry cases cells with the long axons going from one department of a brain to another can be them also are the braking cells, as a rule.
Considerable variability (plasticity) depending on features of the impulsation arriving to synoptic connection is characteristic of chemical synoptic transfer. With a high frequency of an impulsation efficiency of synoptic action on a nek-swarm time increases (the phenomenon of a so-called post-theta-nichesky potentsiation) that facilitates signaling on the appropriate nervous way. Along with it synoptic action can weaken at chemical influences on the prespnaptichesky terminations from other synoptic terminations (presinaitichesky braking). Such processes in general considerably expand funkts, possibilities of chemical synoptic connections.
Principles of integrative activity. The main form of nervous activity are reflexes, or natural reactions to change in surrounding or internal environments of an organism in response to irritation of receptors (see the Reflex). Reflex activity of N. of page submits to a number of the general patterns. First of all, the nature of reflex reaction is defined by type of receptors. Set of receptors, irritation to-rykh causes this type of a reflex, forms the so-called receptive field. The receptive field of a certain reflex can combine both identical and various receptors; the receptors, same on a structure, can belong to various receptive zero. The nature of reflex reaction depends also on features of the operating irritant, in particular its force. Strengthening of irritations leads to increase in number of active nervous elements (the phenomenon of irradiation of excitement). Irradiation is caused by the fact that in the central departments of N. of page there is a large number of interneural bonds nonfunctioning at present; during the strengthening of irritation there is an increase of an impulsation in separate nervous cells and simultaneous involvement in activity of their bigger number.
The nature of reflex reaction can change considerably and depending on a condition of those nervous structures, through to-rye it is carried out. Change of excitability of nervous structures can change reflex reaction not only quantitatively, but also is high-quality. In particular, the page of the center of excitement (e.g., under the influence of hormones) brings emergence into N. as it was shown by A. A. Ukhtomsky, that the irritation of various receptive fields begins to cause the reflex activity characteristic of structures of this center.
Any reflex activity always represents a difficult complex of reflexes interacting and vzai-movliyayushchy at each other. Inevitability of such interaction follows, in particular, from the fact that various types of reflexes are often carried out through the same motor neurons, with use of the same muscles. Motor neurons in this case represent the general final motive way. The general rule of interaction of reflexes at the same time is mutual strengthening unidirectional and mutual braking of opposite reflexes. Funkts, an orientation is defined by the nature of end reflex reaction.
Interaction of reflexes proceeds differently, depending on power of the irritations causing them. If the irritation of each of two receptive fields so poorly that in itself it is not enough for a call of the category in motor neurons, then simultaneous irritation of this field can cause noticeable reflex reaction (the phenomenon of so-called summation, or simplification). The reason of it consists that in the central departments of N. of page at joint irritation of two receptive fields in nervous cells there are space summations of the local synoptic processes capable to a call of depolarization of a membrane in a number of cells, and generation of nervous impulse. Therefore two reflex phenomenons, to-rye in itself are not capable to cause an impulsation of motor neurons, now will cause it and will lead to reduction of the corresponding muscle.
More difficult ratios of reflex reactions take place in that case when each irritation in itself already gives the answer. At the same time each afferent wave in some part of motor neurons causes the category of nervous impulses, and in some part only subthreshold processes. At simultaneous action of two waves the category arises in those motor-neurons, in to-rykh subthreshold synoptic influences are summed up. Therefore total quantity of the discharged neurons will be big, than the algebraic sum of the neurons giving the category at separate activation. The reserve of cells which is in addition joining in the category is designated as on dpo a horn border. In the majority of the reflex reactions connected with action of natural irritations, only the category gives 10 — 20% of the total possible quantity of neurons, and other neurons are in a state podporoto vy synaptic activation. Only in case of substantial increase of reflex irritability of c. the N of page occurs essential redistribution between these groups in favor of the discharged cells.
If the most part of neurons of this structure of a brain is involved in the category, then at interaction of reflexes those neurons, to-rye already generated nervous impulse, cannot repeatedly answer at once. There is partial or full occlusion. Degree of occlusion is expressed as a percentage; at 100% of occlusion overall reflex reaction is equal in size of separate reaction.
At interaction of multidirectional reflexes there is not a phenomenon of simplification, and their braking. The general patterns of brake interaction are similar to patterns of mutual simplification. The weak braking influences mutually facilitate each other; if each reflex wave renders the maximum effect, then there is occlusion of the braking influences. The facilitating and braking interferences between nerve centers in the course of the combined reflex activity were analyzed on the example of a spinal cord by the English physiologist Ch. Sherrington in 1906 and described by it as positive and negative simultaneous induction. Due to the obtaining exact data of rather cellular synoptic processes which are the cornerstone of the corresponding phenomena, these descriptive terms began to be applied seldom.
At the combined reflex activity along with steric interaction of nerve centers the difficult phenomena develop also in time. As I. M. Sechenov for the first time noted, the termination of braking of reflex reaction often is followed by the subsequent its strengthening in comparison with initial level — so-called return. Assumed Ch. Cher ringtone that special central process is the cornerstone of this phenomenon, to-ry it called successive induction. However direct studying of synoptic processes showed lack of a feedforward between switching off of synoptic braking and emergence of opposite effect. Therefore the phenomenon of return began to be considered as result of inclusion of additional reflex influences through more difficult central or peripheral nerve pathways.
In experimental conditions each reflex can be investigated as the independent process which is beginning irritation of a certain receptive field and coming to an end with the corresponding reaction. For this purpose use the receptions allowing to stabilize and simplify as much as possible mechanisms of activity of a brain: isolation of certain sites of a brain by sections, a narcotization of an animal, use of simpler irritants etc.
Under natural conditions each reflex act acts always as a component of more complex system of nervous processes, an ultimate goal to-rykh is the most effective implementation tone or other function of a complete organism. Combination of separate reflex mechanisms in systems is not rigidly fixed and represents the mobile interaction guaranteeing successful performance of each function under constantly changing living conditions of an organism. Important component of such association — a possibility of assessment of result of reflex activity and the alarm system about it in the relevant centers by means of a feed-back. These systems are well studied, e.g., in the motive device where they are presented by receptor formations of muscles, sinews and joints and system of the appropriate afferent ways. The principles of association of reflex processes in more difficult complexes, to-rye can estimate result of reflex activity and on the basis of such assessment to regulate the last, were studied by P. K. Anokhin; the term functional systems was offered them for such complexes (see).
The role of a nervous system in activity of various bodies and systems
Managing activity of N. of page extends to all bodies and systems of an organism and is carried out by all its departments. Simpler forms of this activity are connected with structures of a spinal cord (see), more difficult — with various centers of a brain (see), for to-rykh spinal structures are executive. However course even of those reflex reactions, for implementation to-rykh enough spinal mechanisms, also depends on bonds of a spinal cord with overlying structures. Section of these bonds leads to oppression of spinal reactions (so-called spinal shock).
Reflex mechanisms of a spinal cord initially manage both motive, and vegetative reactions. Efferent signals for motor reactions form motor (motor) spinal neurons, and for vegetative — the sympathetic or parasympathetic preganglionic spinal neurons located respectively in chest or sacral departments of a spinal cord. Motive reflexes of a spinal origin are own reflexes of muscles, protective and nek-ry other reflexes. Own reflexes of muscles arise at irritation of receptor devices of muscle spindles. They lead to the tonic tension of a muscle at its stretching (myotatic contractions), regulating that its length; at an excessive tension receptors of sinews are irritated, causing, on the contrary, braking of tonic activity of motor-neurons (autogenic braking) relaxing a muscle. The receptor device of muscles is under additional, central, control at the expense of an innervation of intrafusal muscle fibers special motor neurons (gamma motor-neurons). Reduction of such fibers regulates intensity of the category of the stretch receptors located on them.
Idiosyncrasy of the reflex mechanisms creating own reflexes of muscles is exclusively high speed of carrying out excitement in them. The afferent nerve fibrils (see) originating from stretch receptors and tendinous receptors have the largest diameter among other fibers and carry out nervous impulses with a speed up to 120 m/s. Besides, the synoptic terminations which are formed these fibers in a spinal cord contact to motor neurons directly, passing inserted cells; there is a so-called two-neural (monosinaptichesky) reflex arc providing the minimum delay (apprx. 0,5 m/s) for synoptic transfer of influences from sensitive neurons on motive. At the same time through the special braking neurons motor neurons of antagonistic muscles are braked.
Among protective reflexes the main place is taken by the bending reflexes directed to protection of an organism from the strong damaging irritations (otdergivany extremities or dropping from a body surface of sources of such irritations). The receptive field of these reflexes is very difficult; the receptors of a skin surface reacting to strong mechanical and thermal irritants enter it. and also the receptors located in the depth of an organism, in particular in the muscular device and internals irritants for to-rykh are disturbances of blood circulation in fabrics, strong mechanical, chemical and other influences. Afferent ways from such receptors are presented by an extensive set of the fibers (which are generally relating to nerve fibrils of group A); often they are conditionally combined in group of offerers of a bending reflex. The central mechanisms of this reflex reaction differ in complexity and include activation of specialized internuncial neurons. At the expense of it there is a broad irradiation of excitement on a spinal cord, and even at irritation of small sites of the receptive field a number of muscles is involved in motor reaction. At rather intensive irritation reflex activity can capture muscles of all extremities, and also trunks. At the same time activation of motor-neurons on the opposite side of a body has opposite character — there is an extensive movement (a crossed extensive reflex) necessary for maintenance of a pose at an otdergivaniye of extremities. If own reflexes of muscles are reflexes of tonic type, then the protective bending reflex belongs to reflexes of ryv-kovy type. Reaction at it arises only at the beginning of irritation and then quickly weakens. The reason of bystry fading of a bending reflex lies in features of functioning of the corresponding internuncial neurons or the terminations of afferent fibers located on them — bystry decrease in efficiency of their synoptic action at repeated excitement.
On the organization spinal rhythmic and position (postural) reflexes are even more difficult. They involve a large number of various spinal centers localized in a number of segments of a spinal cord in activity. At rhythmic reflexes there is the correct alternation of the opposite movements (bending and extension) which are imposed on tonic contraction of certain muscles; an example of such reflexes are motor reactions of «hackling» and «pacing».
The analysis of the central mechanisms of rhythmic reflexes showed that in the most spinal cord the program of periodic switching of excitement on one, on other group of motor neurons is put; the program is provided with interaction of two groups of inserted nervous cells, one of to-rykh is activated in a phase of bending, and another — in a phase of extension of an extremity. These two groups are combined by interneural bonds thus that excitement of one of them is followed by braking another. Each group of neurons in turn sends teams to the corresponding motive nervous cells. Under natural conditions all this difficult mechanism gets into gear under the influence of the teams arriving from the relevant centers of a brain though teams only «allow» its work, but do not determine its content (the last entirely depends on neural structures of a spinal cord).
Postural, or position, reflexes (attitudinal reflexes) unlike rhythmic reflexes are directed on long maintenance of reflex reduction of a muscle for giving to an organism of a certain pose. At position reflexes tonic muscle performance continues for minutes, hours, and sometimes and days without noticeable signs of exhaustion. Especially important role in such reflex activity at mammals is played by upper (I—III) cervical segments of a spinal cord in this connection such reflexes are called also cervical tonic attitudinal reflexes. The detailed description of these reflexes was carried out by the Dutch physiologist R. Magnus (see. Magnus — Klein reflexes ). The receptive field of cervical tonic reflexes are receptors of muscles, and also the fastion covering the cervical site of a backbone. The reflex arc has difficult, polisinapti-cheskpy character, and muscles of a trunk, all four extremities and a tail are involved in response. Besides, considerable reflex influences are transferred from cervical segments to a trunk part of a brain, first of all to the motor neurons innervating eye muscles. A main type of the irritation causing cervical tonic reflexes are various turns and a ducking. Stretching cervical muscles or a fascia, they lead to reflex redistribution of a tone of muscles of extremities and trunks, and also to preservation of the correct orientation of eyes. Cervical tonic reflexes are duplicated by vestibular tonic reflexes.
Vegetative reflex reactions of a spinal cord are carried out through sympathetic and parasympathetic departments of N. of page (see the Autonomic nervous system). The reactions providing regulation of level of blood pressure due to change of a gleam of arterial vessels are most studied (see. Blood pressure). Reflexes arise at irritation of the same receptors, to-rye define emergence of protective somatic reflexes, and are closely connected with them. Apparently, both components of a protective reflex — motive and vascular — are caused by activation in a spinal cord of the same complex of internuncial neurons, to-ry activates, on the one hand, motive, and with another — the somatic preganglionic neurons responsible for vasomotion. Thus, on funkts, to a sign in a spinal cord only vegetative output (efferent) neurons are accurately divided on somatic and. Complexes of inserted cells can be activated by signals of both a somatic, and visceral origin and are in a zealous measure the general for somatic and vegetative reflexes. Such principle of the organization of the central and neural structures finds the reflection and in feelings of the person. At various patol, processes in the internals which are followed by irritation of their receptor structures the patient has pain, to-rye is projected on certain sites of a body surface (see Zakharyin — Geda of a zone). These sites are quite constant and correspond to those segments, in to-rykh there is a convergence of somatic and visceral afferent influences on the general internuncial neurons.
In addition to a vessel of motor reactions, other vegetative reflex reactions also are connected with structures of a spinal cord (reactions of smooth muscles went. - kish. path, digestive glands, etc.) - It is important to note that if in smooth muscles of a vascular wall and in a cardiac muscle these reactions have exciting character, then in smooth muscles went. - kish. a path — braking, causing its relaxation.
Reflex reactions of parasympathetic department of century of N of page are connected with regulation of reductions of smooth muscles of a bladder, generative organs, etc. At the same time the complex combination of spinal reflex processes and the descending influences of the centers of a brain takes place. So, the irritation of receptor structures of a bladder causes the synoptic braking of preganglionic parasympathetic neurons necessary for prevention of a spontaneous urination through a spinal reflex arc. Exciting influences to the same neurons arrive with the big eclipse period through nadsegmentarny structures; in process of strengthening of irritation they accrue more considerably, than segmented braking, and, eventually, begin to prevail in operation on parasympathetic neurons, leading to emptying of a bubble. The internuncial neurons transferring the braking influences on parasympathetic cells can be slowed down by the descending signals arriving from a brain. Parasympathetic neurons of a spinal cord have also vasodilating effect on vessels of cavernous bodies of generative organs, causing overflow by their blood and an erection.
Reflex activity of the rhombencephalon including myelencephalon (see) and cerebellum (see), it is much more difficult than activity of a spinal cord. It is connected with existence in it of a large number of the nervous elements which are not receiving afferent signals directly from receptor systems and not giving efferent signals (a reticular formation of a brain trunk, subcrustal kernels and bark of a cerebellum). They have nervous bonds only with other centers of a brain and are, therefore, a superstructure over primary segmented structure of c. N of page.
The reflex reactions which are carried out by kernels craniocereberal (cranial, T.) nerves back and a myelencephalon, as well as reflex reactions of a spinal cord, on character of a final effect are divided on somatic and vegetative. They are directed, on the one hand, to maintenance of a pose of an organism, and with another — to ensuring perception, processing and a proglatyvaniye of food. The reflexes directed to maintenance of a pose are connected with excitement of receptors of a vestibular mechanism and semicircular channels and are carried out through vestibular nuclei; neurons of vestibular nuclei form the vestibulo-spinal ways which are coming to an end with synoptic connections directly on motor neurons of a spinal cord. These reflexes are subdivided into attitudinal reflexes and reflexes of straightening; they provide change of a reflex tone of muscles at change of position of a body in space and recovery of a normal pose. Along with regulation of a tone of skeletal muscles also the tonic tension of oculomotor muscles is exposed to change that provides preservation of visual orientation in space at change of situation or rotation of a body.
Food reflexes are connected with functioning of kernels V, IX, X, XI and XII couples of cranial nerves, activity to-rykh provides the sequence of processes of chewing, swallowing and advance of food on went. - kish. to a path, and also release of digestive juices.
Activity of the acoustic analyzer is initially connected with kernels of cranial nerves of a metencephal. Kernels are presented by the neural complexes perceiving an afferent impulsation from sound receptors of kortiyevy body of an inner ear. From these neurons the ascending ways transmitting the corresponding signals through intermediate switchings on average and a diencephalon to a cerebral cortex (see) begin.
Regulation of a number of the major functions of an organism, mechanisms a cut is connected with a reticular formation (see) have many similar lines. By microelectrode researches it is proved that in a reticular formation of a myelencephalon complexes of neurons are localized, frequency of depolarization of membranes to-rykh corresponds to a respiratory cycle; in one cells this process corresponds to an inspiratory phase, and in others — an expiratory phase. Specific action on these neurons the level of partial tension of carbonic acid in blood possesses. Increase leads it to increase of rhythmics, and decrease — to its urezheniye. The correct periodical press in respiratory function is provided with periodic redistribution of activity «respiratory» and «exhaling» neurons due to cross interneural bonds (as well as at generation of rhythmic movements by neural structures of a spinal cord). The periodic pulse categories generated in a reticular formation go on reticulospinal ways to motor neurons of respiratory muscles, to-rye are the executive office which is not showing independent automatic activity.
In spite of the fact that the system of neurons of a respiratory center of a reticular formation is capable to automatic activity, it can change substantially the activity under the influence of the impulsation arriving from various afferent systems. Moshchnsh a source of reflex regulation of respiratory neurons of a reticular formation is the afferent system of the most respiratory device presented by the mechanioreceptors which are activated at stretching or compression of lungs (so-called reflexes of Goering — Breyer), and also receptor zones of blood vessels.
In the same area complexes of the neurons participating in regulation of vascular pressure are located. Pulse activity of the separate neurons entering such complexes is naturally connected with reflex changes of a vascular tone: one neurons speed up the activity at increase in the ABP («vasoconstrictive»), and others — at his decrease («vasodilating neurons»). The descending ways formed by such cells go to chest department of a spinal cord where come to an end not on respiratory motor-neurons, and on vasomotor preganglionic sympathetic cells. The system of neurons of a vasomotor center also has high chemical sensitivity, and the frequency of their category is depending on chemical composition of the blood arriving to them. Vasomotor neurons of a reticular formation are subject to intensive reflex influences; the main receptive field for them is the receptor system of vessels, in particular aortic arches, a carotid sine, the mouth of venas cava, etc. (Ludwig's reflexes — Tsion, Goering, Bainbridge). Thanks to these reflex influences at build-up of pressure in arterial system there is a braking of activity of a vasomotor center and decrease in a tone of vessels, i.e. reflex return of pressure to datum level (see. Depressory reactions ). To the contrary, at build-up of pressure in venous system there is reflex strengthening of tonic activity of a vasomotor center — pressor effect (see. Pressor reactions ). Activity of a vasomotor center is closely connected with activity of group of the neurons regulating action of the heart (preganglionic parasympathetic neurons of a motor kernel of a vagus nerve), excitement k-rykh-through the corresponding ganglionic neurons causes braking of cordial activity. Neurons of this kernel also are in a condition of tonic activity, edges is subject to modulation by synoptic influences from vasomotor area.
Neural structures of a reticular formation play an important role and in regulation of somatic functions. X. Megun and J. Moruzzi it was revealed that the irritation of these structures effectively changes, on the one hand, a current of spinal motive reflexes, and on the other hand — activity of bark of big hemispheres, defining transition of the last to the active («awake») or inactive («sleepy») state. These reticular influences also consist from opposite, braking and facilitating, components; they easily change under the influence of such chemical factors as the C02 level in blood and contents in it physiologically active agents. Feature of function of the corresponding reticular neurons is broad convergence in them synoptic influences from various afferent systems in particular bearing signals about strong, the damaging irritants. It leads to their low-specific tonic excitement and the corresponding tonic influences on other departments of c. N of page. Neurons of a reticular formation differ in also high sensitivity to a row pharmacological and drugs (e.g., to barbiturates), to-rye, easily contacting hemoretseptivny group-piro.v.ka of their membranes, change tonic activity of neurons and have a powerful systemic effect on work of a brain.
Neural structures of a cerebellum (see) play an important role in regulation of a physical activity. The neurons of a bast layer of a cerebellum organized in the correct net obtain information from vestibular receptors and receptors of a musculoskeletal system. This information is exposed to difficult processing and arrives to output cells — Purkinye's cells possessing the braking function. Thus, bark of a cerebellum but to a being appears the device of braking of structures, with to-rymi it synoptic is connected, and its influence is carried out by modulation of tonic activity of neurons of own subcrustal kernels, vestibular nuclei and kernels of a reticular formation.
Activity of a mesencephalon (see) is closely connected with the most important distantny receptor function of an organism — sight (see). As well as in a cerebellum, neurons of a mesencephalon are located on its surface, forming cortical multilayer structure with difficult interneural bonds that provides rather complex analysis of visual irritations and the corresponding responses of an organism.
Functions of a mesencephalon at the highest vertebrata significantly changed. It is connected with the fact that the direct ways going from a retina perekhme-shchatsya forward and come to an end with the most part in kernels of a diencephalon (cranked bodies). Therefore behind a mesencephalon only the part of visual function connected generally with regulation of movements of eyes remains (by means of the oculomotor neurons innervating eye muscles). At the same time with development of acoustical system on average a brain intermediate kernels of acoustical ways are formed; they are localized in the lower hills a chetverokholmiya, the mesencephalon of the highest animals making a tire. In a reticular formation of the basis of a mesencephalon the complexes of neurons with more specialized projections (a red kernel, an intersticial kernel, etc.) which are closely connected with regulation of certain motive functions of an organism are located. These neurons are under a direct impact of bark of big hemispheres and subcrustal kernels and form system of extrapyramidal motive ways (see. Extrapyramidal system ).
Diencephalon (see) is the complex structure including a huge number of various cellular accumulations with diverse interneural bonds; it is localized around the third cerebral cavity. The main formations of a diencephalon are thalamus (see) and hypothalamus (see). Funkts, value of thalamic kernels is defined by character of projections of axons of their neurons. The kernels giving projections in bark of big hemispheres (projective) represent a component of the main afferent systems providing transfer and processing of touch information on its way to sensitive areas of bark of big hemispheres. Practically all afferent systems, except for olfactory, before the introduction in bark pass through kernels of a thalamus. Destruction of these kernels leads to full and irreversible loss of the corresponding types of sensitivity. Projective kernels have the topical organization so each point of the receptive field of this system is projected in a certain group of neurons of a kernel.
Along with projective neurons the thalamus contains a large number of neurons, axons to-rykh establish connection with other subcrustal structures or, going to bark, dissipate on its extensive areas. Complexes of neurons of this kind designate as nonspecific kernels of a thalamus. Their activity can be caused by signals from various afferent systems and has no space and specific character; on the other hand, activity of neurons of this type has the facilitating effect on cortical cells, increasing their excitability and ability to answers to the impulsation arriving through projective kernels. This their function is comparable with action of a reticular formation of a brainstem in this connection one researchers assume that the reticular formation has effect on bark of big hemispheres through nonspecific kernels of a thalamus, others consider these two systems as separate, each of to-rykh independently carries out a peculiar influence on bark of big hemispheres.
At the expense of bilateral ties with other subcrustal structures the thalamus manages a number of the complex-reflex functions which are not connected with signaling in an end brain and demanding integration of somatic and visceral reactions.
Especially important role in this process is played by structures of hypothalamic area — a difficult complex of kernels with efferent pathways to trunk structures of a brain, and also to the leading endocrine system — to a hypophysis (see). Due to such bonds the hypothalamus performs function of one of the highest centers of integration of vegetative functions, to-rye further are regulated sympathetic and parasympathetic by departments of century of N of page, and also hormonal influences. Thermal control, a feeding and sexual behavior etc. belong to such functions. Implementation of all these functions is followed by a special emotional state — • satisfaction. All complex of the central processes, to-ry induces an organism to look for satisfactions or to avoid adverse situations, is designated as motivation (see). An essential role in motivation along with reflex influences from the corresponding receptor systems is played by physical and chemical impacts on neurons of hypothalamic area from the blood coming to it.
The highest forms of activity of a nervous system. An end brain — the newest N.'s structure of page in the evolutionary relation. At the lowest vertebrata it has only sensitive (olfactory) function. This function behind it remained at the highest animals and at the person, however those sites of hemispheres, to-rye are to some extent connected with sense of smell (old bark), at them are insignificant on volume in comparison with the new structures which do not have relations to sense of smell.
Old bark at the highest animals, except actually Olfactory ways, includes nek-ry areas of the medial party of hemispheres — a zone crinkle, a hippocampus, an amygdaloid kernel, etc. (see. Limbic system ). On neurons of these structures there is a convergence of various afferent influences, and the irritation of neurons causes essential changes of a number of the main functions of an organism (cardiovascular activity, breath, etc.). Therefore it is supposed that structures of old bark are connected with the highest regulation of the functions directed to maintenance of constancy of internal environment of an organism (homeostasis); they have close relation to reproduction and an affective behavior.
The main structural feature of new bark is the huge number of its cellular elements (more than 10 billion is at the person) definitely grouped and oriented. In it touch zones are allocated, to neurons to-rykh the main afferent systems (somatosensory, visual, acoustical, flavoring), and the motor zones sending motive teams on the pyramidal and extrapyramidal ways going to a brainstem and a spinal cord are projected. At the person specialized sites of new bark are connected with implementation of such difficult motive function as the speech. Afferent projections to neurons of touch zones are organized by the topical principle; neurons of these zones together with the conduction paths and the corresponding receptors which are coming to an end on them represent detectors of these or those qualities of irritants. Neurons of .motorny zones also spatially are specialized and send the signals to certain executive neurons.
Along with these local functions in bark the highest forms of nervous activity demanding integration of all signals coming to it and their comparison to traces from the irritants operating earlier are carried out. Here the subjective image of the outside world forms and there are teams managing all activity of an organism according to the irritants which are directly operating on it and its individual experience. The general principles of the organization of cortical processes at higher nervous activity (see) are established by I. P. Pavlov. Qualitative difference of century of N from simpler forms of nervous activity is short circuit in bark of conditioned-reflex (temporary) nervous bonds, to-rye for the emergence respectively two centers of excitement demand a combination of conditioned and unconditional excitators and emergence. Cellular mechanisms of short circuit of temporary communication are still insufficiently studied; during the studying of processes in separate cortical neurons any qualitatively excellent lines in comparison with neurons more «low floors» of N. of page are not revealed, to-rye could be the cornerstone of ability of bark to uslovnoreflektorny put bodies of a nost. II re a bottom of l and-gayut that such features are under construction not on properties of separate cells, and on features of their system interaction and that the mechanism of formation of temporary bonds can be found only in system of nervous cells. Mental activity also arises as result with pe tsif and che with to about y di of N and m and to and p r about c of e with with about in excitement and braking, characteristic of bark of big hemispheres and leading to association of its neurons in special mobile systems. Apparently, there are no bases to consider mental processes as function of separate cortical cells; such point of view would represent the simplified, mechanistic approach to the solution of this elozhneyshy problem.
Studying of changes of activity of separate neurons in various areas of bark, in particular in so-called associative areas, confirmed the assumption that during development of a conditioned reflex in bark of big hemispheres characteristics of bonds between neurons really change. However it does not allow to judge that it changes in interneural bonds. Also cellular mechanisms of long preservation of traces of last activity are not clear that it is characteristic of higher nervous activity (see. Memory ).
the Chemical structure and a metabolism in various elements H. of page is studied unequally. The greatest number of researches on these questions is devoted to a brain; data on a spinal cord, the autonomic nervous system and peripheral nerves have fragmentary character.
Chemical composition of various formations of a nervous system. Nervous cell. The body of a nervous cell contains apprx. (>5 — 70% of water. Apprx. 70% of size of the dense rest make proteins (see). Proteins of neurons very much refeporeiiHbi. Among them complex proteins — nucleoproteids, lipoproteids, phosphoproteins and glycoproteins are found. The proteins characteristic only of nervous cells, such as proteins 14-3-2 and 14-3-3, tubulin, etc. are found. From nerve terminations aktomiozinopodobny protein neyrostenin, is secreted by making 8 — 10% of all proteins which are a part of nerve termination. Lipids make apprx. 20 — 25% of size of the dense rest of a nervous cell. Are presented lipids (see) almost all classes. The most numerous group of lipids is made by phospholipids (about 75% of total quantity of lipids); from sterols the cholesterol (apprx. 10%) which is in a stand-at-ease is found. Concentration of galactolipids is equal to about 2%. As a part of plasma membranes of neurons, membranes of the trailer terminations and synoptic bubbles gangliosides contain.
Kernels of nervous cells contain practically all DNA, except for its small amount which is in mitochondrions and plasma membranes. At the same time the content of DNA in various departments of N. of page does not change.
In nervous cells all main types of RNA are found. Content of RNA in neurons depends on their sizes. So, large cells of Deyters, motor-neurons of a spinal cord and ganglionic cells of a supraoptic kernel contain in one cell respectively to 1550, 530 and 70 pg RNA. In neurons and a neuroglia distinctions as a part of the bases of RNA are found: in neurons of a kernel of a hypoglossal nerve of RNA richer tsitoziny, and RNA of a neuroglia — adenine and uracil.
Structural component of a nervous cell is the myelin cover of nerve fibril. The myelin has a unique chemical structure. In it contains lipids more, than in any other membrane structure — to 78 — 80% of dry weight. A large amount of cerebrosides and tserebrozidsulfa-comrade Glitserofosfatida of a myelin in comparison with the elements forming gray matter of a brain contain in a myelin only 1/6 part of total quantity polyunsaturated fat to - t. In sphingolipids of a myelin in 5 — 9 times more long-chain (19 — 26 carbon atoms) fat to - t, than in sphingolipids of gray matter; in a myelin only of 1 of 17 fat to - the t is poline-saturated whereas in gray matter — 1 of 5. Such structure of a myelin partially explains extreme stability of myelin covers: the polyunsaturated lipids reducing stability of membranes are present at it in low concentration whereas the long-chain sphingolipids increasing stability of membranes — in high concentration. Other important component of a myelin are proteins, preferential main character. The solubilized lipoprotein fraction of a myelin at an electrophoresis has the same mobility as albumine.
The glycogen is concentrated generally in a neuroglia, and neurons practically do not support him or contain in the minimum quantity. Low-molecular weight compounds of a nervous cell are presented by free amino acids, peptides, mineral substances (To +, Na+, Sa2+, Mg2+, C1", microelements).
Extremely important role in activity of a nervous cell is played by chemical transmitters of nervous impulses — mediators (see). From them acetylcholine, dopamine, noradrenaline, serotonin, glutaminic and at - aminobutyric to - you, glycine, etc. are most widespread. Acetylcholine in N. is distributed by page unevenly: its high content is noted in a cerebral cortex, a thalamus, front hillocks a chetverokholmiya, the bridge; in a myelencephalon, a hypothalamus and a spinal cord it is approximately twice less, than in a cerebral cortex; in bark of a cerebellum its concentration is insignificant. Glutaminic to - that is found approximately in identical quantities in a cerebellum, a hippocampus, an average and a diencephalon and a cerebral cortex; its contents in a trunk is much lower. Concentration of glycine in a back and myelencephalon 3 — 5 times higher, than in the departments located rostralny a myelencephalon. In a brain kernels — accumulations of bodies of the nervous cells containing preferential this or that mediator are found. So, in locus caeruleus bodies of noradrenergichesky neurons, in kernels of a seam — the serotonergic neurons sending axons practically to all sites of a head and spinal cord in nek-ry sites of a mesencephalon — bodies of the dofaminergichesky neurons innervating cortical educations, a kernel having a tail, a striate body, olfactory hillocks and an additional kernel are concentrated.
The smallest maintenance of noradrenaline is peculiar to a cerebral cortex. Basal kernels (an almond, a septal kernel), average both a myelencephalon and the bridge differ by 2 — 4 times, and a hypothalamus and a number of kernels of a diencephalon by 5 — 10 times in the maintenance of noradrenaline, big in comparison with bark.
Dopamine in insignificant quantity can be found practically in all areas of a brain; its high content is found in a kernel having a tail, a shell, black substance, nek-ry basal kernels.
Concentration of serotonin in a brain decreases in the caudal and rostral direction. High content it is noted in various departments of a myelencephalon, the bridge, a mesencephalon, thalamus, hypothalamus and low — in basal kernels, bark of hemispheres and a cerebellum. In N. of page there are neurons, function of a mediator in to-rykh presumably perform taurine, adenosine, substance P, opiate polypeptides (see. Opiates endogenous ), histamine and nek-ry others.
The mediator which is allocated under the influence of nervous impulse in a synaptic gap and contacting a receptor on a postsynaptic membrane after the action quickly disappears from a synaptic gap and is inactivated due to splitting by the corresponding enzyme, capture the next glial cells or in the way of the return capture by a presynaptic part of a synapse (see).
Highly specialized structure of a nervous cell are receptors — difficult proteinaceous glyco - the lipidic complexes which are built in synaptic membranes. Linkng of a mediator with a receptor causes a number of composite reactions, to-rykh depolarization or hyperpolarization of a membrane of a nervous cell is a consequence (see. Membranes biological ).
In a nervous cell there is a constant transfer of various connections synthesized in her body in axons, dendrites and synapses by means of aksoplazkhmatichesky current. Specialized structures — neurofilaments and mikrotubula participate in axonal transport, protein tubulin is a part to-rykh. Axonal transport of bubbles, mitochondrions, proteins, nucleinic to - t, enzymes and other connections, and also a possibility of retrograde transport of substances from nerve terminations to a neurocyton are proved.
Neuroglia. Cells of a neuroglia play an important role in biochemical, transformations of various substances into N. of page. The solid residue of cells of a neuroglia is equal to about 20%; apprx. 50% of a solid residue make lipids that is about 1,5 — 2 times higher, than in neurons. All classes of lipids are found in a neuroglia. Protein content in cells of a neuroglia fluctuates from 30 to 50% (in a solid residue). Neyrospetsifi-chesky proteins are revealed: protein of GFA (glia fibrillary acid protein, or acid fibrous protein of a glia) and protein S-100. Content of DNA in kernels of neuroglial cells approximately same, as in neurons. Content of RNA fluctuates depending on the size of cells. In a neuroglia practically all glycogen of N. of page is concentrated. Cells of a neuroglia possess more active system of capture of amino acids, than neurons. Content of ATP is at the same level, as in neurons (see. Neuroglia ).
Peripheral nerves. Content of proteins in various peripheral nerves fluctuates from 110 to 150 mg! is fresher than fabric. The proksimodistalny gradient of content of phosphoproteins is established. Collagen makes 40 — 45% of a solid residue of peripheral nerves. It is localized preferential in a myelin cover. Apprx. 20% of total quantity of protein falls to the share of soluble proteins. Protein S-100 is found. The maintenance of lipoproteids in various nerves at different types approximately identical — 0,45 — 1,15 mg! (fresh fabric). Also neurokeratin is found. The general protein content in peripheral nerves is lower, than in general on tissue of a brain, but the content of collagen is several times higher, than in tissues of a brain. Elektroforegramma of soluble proteins of peripheral nerves differs from elektroforegramm proteins of white and gray matter of a brain, cerebellum, a trunk and a spinal cord. The maintenance of lipoproteids is much lower, than in white matter of a head and spinal cord.
The maintenance of the general lipids and phospholipids in peripheral nerves of mammals makes respectively 167 — 215 and 22 — 139 mg! is fresher than fabric. Nenemiyelinizirovan-nye poorly myelinized peripheral nerves contain apprx. x / 6 total quantity of lipids and phospholipids in the myelinized nerves. Cholesterol, the general phospholipids and cerebrosides make in the sum apprx. 95% of total quantity of lipids, other 5% are presented by triglycerides. At mammals a large amount of cholesterol is found (11 — 48 mg! is fresher than fabric). From sterols only cholesterol is found. The molar ratio cholesterol — phospholipids — cerebrosides makes 1:1: 0,5, i.e. approximately same, as in a brain. Gangliosides are found. The maintenance of the general lipids and phospholipids in peripheral nerves is lower, than in back, but above, than in a brain. N. vagus is the only nerve, to-ry on structure of lipids is similar to white matter of a brain. In nerve fibrils various carbohydrates (a glycogen, glucose, fructose, mucopolysaccharides), free amino acids are found (but in smaller concentration, than in a brain), various phosphorus compounds, and also acetylcholine, noradrenaline, a histamine, substance P and some other mediators, contents to-rykh depends on a condition of an animal and type of the studied nerve.
Spinal cord. The biochemistry of a spinal cord is studied poorly. Water content in a spinal cord makes about 70%, a squirrel about 10% (solid residue). Proteins of the main character represent about 1% of all proteins of a spinal cord. Various free amino acids contain. The quantity of lipids makes about 2/3 from a solid residue of a spinal cord. All classes of lipids are found. In a spinal cord of the person caudal and cranial decrease in maintenance of lipoproteids is described. The glycogen in a spinal cord is twice less, than in a brain. Concentration of acetylcholine in a spinal cord approximately same, as well as in other departments of N. of page. In a spinal cord increase in maintenance of noradrenaline and serotonin in the caudal and cranial direction is noted.
Autonomic nervous system. Researches on biochemistry of century of N of page are single and connected generally with studying of the nature of the substances performing mediator function in sympathetic and parasympathetic its departments.
In the terminations of all parasympathetic and preganglionic sympathetic nerve fibrils, and also the postganglionic sympathetic fibers innervating sweat glands, the main mediator is acetylcholine. In sympathetic gangliya acetylcholine is in three forms: free, unsteadily connected with proteins and ready to immediate release, strongly connected with proteins. Acetylcholine which is synthesized in a body of a nervous cell is transferred by axonal current to nerve termination. In a ganglion contains in rest apprx. 10 mkg of acetylcholine 1 g fresher than fabric; at activation of a ganglion contents it repeatedly increases.
In the terminations of postganglionic sympathetic fibers, except for innervating sweat glands, a mediator are catecholamines — noradrenaline and probably adrenaline. Gangliya contain 7 — 8 mkg of noradrenaline and 0,4 mkg of adrenaline is 1 g fresher than fabric. In adrenergic nervous cells noradrenaline is in two forms — labile and connected and is stored in granules — big and small. On chemical structure of a granule of adrenergic neurons are similar to granules of chromaffin cells of adrenal glands, differing from them only in the smaller content of ATP. High content of adrenaline in a mesenteric node and gangliya of an abdominal brain is noted.
A metabolism in various formations of a nervous system. All formations of a nervous system differ in rather high metabolic activity. At the same types activity of breath of cuts of a cerebral cortex, a cerebellum and basal gangliyev has approximately identical intensity. In a spinal cord activity of breath is twice less, than in bark, and unlike a brain sharply decreases with age. Respiration intensity of peripheral nerves makes apprx. 10% of breath of bark whereas peripheral a ganglion differ in rather high speed of oxygen consumption. Neurons of a brain and spinal gangliyev consume oxygen with a speed of 260 — 1080, glial cells 50 — 200, and nerve terminations of 50 — 60 µmol! hour (on 1 g of fresh weight). Mitochondrions of neurons and cells of a neuroglia have intact! a cycle Tricarboxylic to - t (see. Tricarboxylic acids a cycle) the glutamate, succinate, pyruvate and and - ketoglutarate as substrates are also capable to oxidize. However if in neurons these substrates maintain approximately identical and rather high speed of oxygen consumption, then in cells of a neuroglia respiration intensity is high in the presence of succinate and is low with the pyruvate and a glutamate used as substrate. It is shown that in a brain there are at least two metabolic various cycles of Tricarboxylic acids: speed of oxygen consumption in one of them is equal 75, and in another apprx. 20 µmol! hour (is 1 g fresher than fabric). The main metabolite of N. of page is glucose. Glycoclastic activity of nervous and neuroglial cells approximately same, as well as cuts of a cerebral cortex; it makes apprx. 200 µmol of C02 at 1 o'clock (is 1 g fresher than fabric).
Proteins H. of page are exposed to continuous synthesis and disintegration. The half-cycle of their life makes 1 — 16 days (at proteins of a spinal cord it 20 — 40% higher, than at proteins of a brain). Activity of inclusion of radioactive labels in proteins of a spinal cord is lower, than in proteins of a brain, but above, than in proteins of peripheral nerves. Activity of biosynthesis of proteins in neurons is several times higher, than in a neuroglia. Hydrolysis of proteins in N. by the village is carried out by acid and neutral proteinases, and activity of these enzymes in neurons is higher, than in a neuroglia, and in a spinal cord below, than in head. At the same time cells of a neuroglia in comparison with neurons have bigger activity of capture of amino acids. Speed of capture and accumulation of amino acids in cuts of a spinal cord is lower, than head. Activity of K+, Ha +-ATF-azy is higher in a glia, than in neurons.
Nervous cells and cells of a neuroglia, and also all formations of a nervous system possess active systems of synthesis and disintegration of all classes of lipids. Biosynthesis of phospholipids in nervous cells is higher, than in a neuroglia. Biosynthesis of lipids in peripheral nerves is less active, than in a head and spinal cord.
The pathological physiology
Patol, N.'s physiology of page studies mechanisms of damage of N. of page, pattern of its activity at different damages, mechanisms of compensation and recovery. Its task includes also creation of pilot models of various forms of pathology of N. of page and development of the principles of pathogenetic therapy.
The pathogenic factors causing N.'s damages by page can be exogenous or endogenous. Treat exogenous biol, activators (viruses, microbes), different toxins, environmental factors, excessive irritations, etc.; the increasing value for pathology of century of N of of the person is gained by the accruing overloads operational information. Internal causes can be primary and have independent value (e.g., hereditary forms of pathology, system and regional disturbances of blood circulation and microcirculation, autoimmune processes and so forth) or secondary. Also combined effects of factors of both groups are possible: influence of exogenous agents on is endogenous the prepared background (hereditary predisposition, decrease in resistance as a result of the former pathological processes and so forth). Owing to features of the structurally functional organization of c. N of page the place of primary damage of N. of village and the place a wedge, manifestations of the caused pathological process can not match.
In pathological physiology of N. of page it is possible to allocate: pathological processes at the cellular level, pathology of intercellular interactions, pathology of the system relations, changes neurochemical, processes (neyropatokhimiya), compensation of the broken functions, mechanisms of recovery, the principles of pathogenetic therapy and experimental modeling.
Pathological processes at the cellular level can be caused by pages, nonspecific for N., pathogenic factors, to-rye damage metabolic processes and in other fabrics (a hypoxia, disturbance of microcirculation, etc.) and specific agents (neurotoxins, Neurotropic pharmakol, substances, specific antibodies, etc.).
Various damaging influences can cause disturbance of the main property of the neuron defining it funkts, value — disturbance of the mechanisms of electrogenesis of a neyronalny membrane providing creation of transmembrane potential, generation and distribution of impulses. At the same time there can be multidirectional changes of passive ionic currents. So, at damage of natrium channels of an electroexcitable membrane ability to generation of pulse activity is broken: it can be completely suppressed at an inactivation of these channels (e.g., at action of a tetrodotoksin) or is significantly transformed at activation of channels (effect of batrakho-toxin, veratridine, etc.). Changes of properties of potassium channels (e.g., at action tetraethyl of ammonium, 4 aminopyridines) define shifts of transmembrane potential and significantly influence the nature of pulse activity. It is supposed, in particular, that changes of permeability of a membrane for potassium ions cause the nature of changes of activity of the leading neurons or their population. An essential role in these processes is played by disturbance of active transport of ions (see) which fermental basis is Na which is built in a membrane, K-aktiviruye-maya ATP-ase. Its inhibition, napr, effect of specific inhibitors — cardiac glycosides leads to generation of epileptic activity. It is shown that in the epileptic centers of various origin at a certain stage of their formation the inhibition of Na, K-ATP-ases takes place; at action of anticonvulsants along with disappearance of epileptic activity also activity of Na, K-ATP-ase is recovered. A pathogenetic role in emergence of a hyperactivity of neurons (their epileptization) is played by changes of balance of calcium ions — its strengthened receipt in a cell along with increase in maintenance of potassium ions out of a cell.
Synoptic processes are influenced significantly by disturbance of hemochuv-stvitelny electrogenesis in postsynaptic membranes both in exciting, and in brake systems. This process makes a basis of many forms of pathology of c. the N of page, but is implemented by different mechanisms (blocking of chemoceptors or decrease in their sensitivity). In exciting cholinergic synapses blockade of hemochuvst-vitelny electrogenesis is carried out by kurarepodobny means, and-bungarotoksinom (due to linkng with N-holinoretseptorami) or atropine (due to linkng with M-holinoretseptorami). The sequence of data demonstrates that at myasthenia N-holinoretseptory of the neuromuscular device are a target of cytotoxic action of autoantibodies, representing, thus, the fundamental pathogenetic unit. In brake synapses blocking of receptors is carried out by strychnine or picrotoxin, bikukuli-number. Decrease in sensitivity of chemoceptors can develop at the strengthened activation of postsynaptic structures mediators, and also pharmakol, means.
At disturbance of conductivity in exciting synapses there are effects funkts, losses, at disturbance of conductivity in brake synapses — effects of a disinhibition (a secondary hyperactivity of neurons). Similar changes arise at disturbances of activity of presynaptic structures. These structures are, as a rule, more sensitive to various pathogenic influences, than postsynaptic educations and therefore they at many forms of pathology are structures targets. Patol, changes can arise owing to damage of synthesis of the transmitter, at activation of emission of the transmitter, exhaustion of its stocks, disturbances (blockade) of the mechanism of secretion of the transmitter. Especially suffers at pathogenic influences the tormozny presynaptic device. Selective activation of the secretory device snake poisons (| 3-bun-garotoksin) cause, poison of a karakurt, etc. Strengthening of emission of the transmitter can arise at early stages of a hypoxia, at disturbances of microcirculation; further there is an oppression of secretion of the transmitter. Blockade of allocation of a mediator (spontaneous and caused) is observed at action of such specific pathogenic neurotoxins as botulinic and tetanic, also at nek-ry types of defeats of the neuromuscular device at the person (e.g., at Lambert-Eaton's syndrome, at primary defeats of motor-neurons, etc.). Separate links of the mechanism of secretion of mediators — electrosecretory process, education on an inner surface of a presynaptic membrane of aktomiozinopodobny protein or disturbance of its kontraktilny properties can be a target of action, about the Crimea connect an exocytosis of mediators and their circulation.
The strengthened peroxide oxidation of lipids — nonspecific pathogenetic origins of nek-ry forms of pathology of N. of page. A hypoxia and excessive funkts, loadings are the most common causes of the strengthened free radical oxidation leading to formation of toxic peroxides of lipids. The strengthened peroxide oxidation of lipids of neyronalny membranes involves damage of membranes and patol, increase in their permeability. All these factors lead to escaping of a cell of ions, biologically active agents (mediators, peptides, enzymes and so forth) that involves further development patol, process — involvement in it of new neurons, disturbances in system of microcirculation, formation of autoantibodies on neyronalny antigens, development of secondary autoimmune aggression etc. Suppression of the strengthened peroxide oxidation by antioxidants reduces weight of a course of the basic pathological process that is observed at a number of forms of pathology of N. of page (epilepsy, Demyelinating encephalitis, ischemia of a brain and so forth).
Autoimmunonatologichesky processes are among the general mechanisms of defeat of N. of page. Cerebrospinal liquid contains T - and V-lymphocytes, immunoglobulins of various classes, cells suppressors, zero cells and other elements of the immune system providing a cellular homeostasis of c together with glial cells. N of page. At various damages of c. N of page can be carried out specific autoimmune reactions in relation to nervous tissue. The ratio of humoral and cellular components of an immune response at different forms of pathology can be various. At development patol, processes in N. of page sensitivity of leukocytes and monocytes to brain antigens increases. The lymphocytes allocated from an organism, sensibilized with brain antigens show high specific tropism to nervous cells in culture of fabric.
Essential conditions of formation of antibrain antibodies and emergence them in blood is disturbance of an integrity of a blood-brain barrier (see) and damage of nervous and glial elements. Possibility of autoimmune pathology of c. N page and its nek-ry features are defined also by the fact that tissues of a brain and nek-ry internals have a number of the general cross antigens in this connection there is a probability immunnogo damages of c. N of page at nek-ry types of pathology of internals.
In the antigenic relation the neuron is very diverse: in an experiment receive antibodies to its different structures. In the conditions of natural pathology an essential role is played by antibody formation to antigens of a neyronalny membrane. So, it is shown that the gangliosides localized on a membrane of neuron have considerable antigenic properties; impact of protivogangli-ozidny antibodies on a cerebral cortex causes emergence of the centers of epileptic activity.
Implementation of a cytopathogenic effect of antibodies at their connection with antigen requires participation of a complement. Degree of the damaging effect can be modulated by additional depolarization or hyperpolarization of a membrane, potassium ions and calcium, and also novocaine, geparinokhm and other means. Reaction to the autoimmune cytotoxic attack is usually shown in the form of initial depolarization of a neyronalny membrane, and at the continuing its damage — the subsequent oppression and alteration, up to destruction. If process is limited to depolarization, then there can be centers of epileptic activity in the form of generators patholologically of the strengthened excitement. Therefore in an experiment standard effect at introduction of antiserums to a brain is epileptic activity, edges can cause convulsive attacks; specific forms of pathology at the same time are defined by the system activated by the centers of excitement arising in it.
At cytotoxic damage of neuron peroxide oxidation of lipids of its membranes amplifies, there is «leak» from neurons of various biologically active agents. One of them (e.g., lizo-somalny enzymes) can cause damage of the next cells, others (e.g., structural proteins) — to play a role of secondary antigens. At cytotoxic damage oxidation-reduction processes considerably suffer. In an immunopathology the local disturbances of microcirculation arising or initially — are of great importance at action on vascular system of antibodies, specific to it, or for the second time — owing to allocation from the damaged cells of a histamine, bradikinin and other vasoactive substances (see. Mikretsirkulyation ).
Special value has education of new antigens in nervous tissue at N.'s pathology of page. Peculiar, so-called intermediate antigens are formed in a brain at virus and inf. pathologies, and also at allergization. N.'s defeats by the village at patients with an allergy are described, to-rye disappeared after specific desensitization.
Emergence in blood of antibodies to brain antigens or substances, complementary to antigens, is established at epilepsy, schizophrenia, disturbances of cerebral circulation, a hypoxia of a brain, ischemic strokes, hepatocerebral dystrophy, a side amyotrophic sclerosis, multiple sclerosis, neuritis and so forth. Even at an emotional stress if it proceeds it is long and intensively, in blood there are substances which are complementary contacting antigens from brain fabric. Apparently, at many if not at all, forms of pathology of N. of page in the presence of the corresponding conditions there are antibodies against tissues of a brain. Immune responses can have character of primary or secondary response and play a role of an essential or additional pathogenetic link. With participation of this mechanism the myasthenia, allergic encephalomyelitis, etc. are among diseases. At a number of diseases the role of autoantibodies remains still not clear. It must be kept in mind as well that immunol, reactions are mechanisms not only protection (the c providing a homeostasis. N of page), but also immune aggression.
Dystrophic processes in N. are also implemented by page at the cellular level. Practically there is no such form of pathology of N. of page, at a cut in this or that look there would be no dystrophic process. An important role in development of dystrophic process is played by dysfunctions of synapses. Presynaptic terminal is the secretory body allocating not only mediators, but also other substances necessary for implementation of a number of processes including plastic processes in postsynaptic structures — taknaz.tro-fogena. The cosecreted substances exercise at the same time control of the course of actually trophic processes in postsynaptic structures, behavior of glial or connective tissue cells, and also behind a condition of a local macrovascular bed — i.e. all structures providing transport of substances from blood and exchange between nervous and glial cells. Dystrophic process can arise at damage of any of the listed links of trophic system of neuron.
The important mechanism of neyrotrofi-chesky processes is specific to N. the page bilateral bystry axoplasmatic transport of intracellular organellas and various substances, including, perhaps, and special trofogen, to-ry is carried out by cytoplasmatic system of microtubules and microfilaments. Their damage (e.g., in an experiment at influence by mitotic poisons colchicine or vinblastine) breaks an axoplasmatic current and causes a number of features of dystrophic changes on both sides of synoptic contact. The postsynaptic structure renders, in return, trophic influence on the innervating its neuron so the closed trophic contour with bilateral ties is created. Resistant, damage of any link of this contour leads a не-комиенсируемое to dystrophy, edges can be irreversible. So, in experiments on culture of fabric it is shown that if the burgeoning shoot of neuron does not come into contact with a myocyte, then the neuron perishes. Opening of trance-sinaptichesky transition of substances from neuron in neuron with axonal current allows to assume existence of special, still unknown form of the organization II. page in the form of the huge trophic neyronalny network connected as well with peripheral bodies. It is possible to assume that this device plays an essential role in N.'s activity by the village and its disturbances.
The parabiosis for the first time described by H. E. Vvedensky (1901) — a peculiar condition of N. of page, in Krom the phenomena and normal, and patholologically changed (find the reflection up to deep oppression and death) activity of nervous tissue. Its main stages — ek-for lt and c ioiny, leveling, paradoxical and a stage of braking — are standard stages of the process arising under the influence of various pathogenic agents on a nerve (see the Parabiosis). Similar stages can be tracked also at change funkts, conditions of formations of c. N of page in the conditions of pathogenic influences. They are close to phases, to-rye are allocated by I. P. Pavlov in the analysis of various clinical and experimental forms of pathology of century of N of (paradoxical, ultra-paradoxical, leveling).
A. G. Ivanov-Smolensk (1974) suggested to use them for the analysis in neuro dynamic psychiatry.
The Denervatsionny syndrome arises owing to loss of nervous influences on these or those nervous structures or peripheral fabrics. Denervation (see) can be anatomic or chemical. An essential sign of a syndrome is sensitization of denervated structures to the mediator produced switched off nervous a bombway, and also to other biologically active agents (Kennon's law — Rozenblyuta). Private expression of this law is increase at section of a motor nerve of sensitivity of all muscle fiber to acetylcholine due to emergence of the receptors which are absent normal along fibers (the phenomenon of so-called spreading of receptors); the trailer plate at the same time disappears. At denervation there are characteristic phenomena — fibrillation of a denervated muscle (weak separate reductions of muscle fibers) and tonomotorny effect of Vyulpian — Geydengayna who is that after section and the subsequent degeneration of a hypoglossal nerve at a dog the irritation of the peripheral end of a lingual nerve which is followed by allocation of acetylcholine involves tonic contraction of muscles of language that does not happen normal. Besides there are profound changes in metabolism and structures of cells, inherent in dystrophic process; there are signs characteristic of early stages of ontogenesis of this body. These processes, obviously, are caused by a disinhibition of the respective sites of a genome of cells of denervated education since the substances inhibiting activity of the genetic device and, thus, synthesis of nucleic acids and proteins prevent emergence of the described phenomena. The Denervatsionny syndrome is important in activity of nervous structures at the corresponding forms of pathology: their hyperexcitability and the perverted reactivity, decrease in efficiency of action at prolonged use of the pharmacological means blocking these or those receptors is connected with it. On the other hand, increase in sensitivity of denervated neurons can have compensatory character and be the mechanism promoting recovery funkts. bonds and their normalization at action on these neurons of biologically active agents.
Pathological lability of a nervous system — see. Lability .
Pathology of intercellular interactions. Deafferentation of nervous structures treats the phenomena of denervation, but has the characteristic and very important pathogenetic signs allowing to allocate it in an independent pathogenetic syndrome. The main sign of this syndrome is the increase in excitability and activity of deafferentirovanny neurons caused by weakening of brake control to-ry in normal conditions constantly is supported by an afferent impulsation on certain fibers (e.g., the impulsation on thick fibers of group of Aa provides tormozny control of receipt in c. N of page of an impulsation on thin myelin ABP and amyelinic S-fibers in system of an afferent entrance in a spinal cord). Weakening of brake control at loss of an afferentation can happen at all levels of switchings of an afferent flow of c. N of page Rastormozhenny neurons get a hyperreactivity to the impulsation coming from different sources. So, after section of back roots the extremity on the party of a deafferentation makes the movements in a step with breath (Orbeli's phenomenon — Ginetsinsky), swallowing, etc. Activity of deafferentirovanny neurons during reaction korrigirutsya insufficiently owing to lack of the feed-back provided by an afferentation. Populations of deafferentirovanny neurons can create generators patholologically of the strengthened excitement, one of ways of suppression to-rykh is recovery of afferent inflow. Use this method, in particular, for suppression of the pain syndromes caused by hyper activation of nociceptive system the generators arising at loss of an afferentation.
The disinhibition of nervous structures can arise at loss of the tonic influences providing functional and trophic control. Special value in this respect has disturbance of specialized brake mechanisms. Disturbance of postsynaptic) braking can happen at damages of mechanisms of education or secretion of brake mediators (glycine, GAMK, etc.), at blockade of their receptors on a postsynaptic membrane. Effects of the tetanin breaking the spontaneous and caused secretion of glycine, GAMK, dopamine and other transmitters the presinaitichesky device can be an example of damages of brake mechanisms of the first type. Blockade of glycine receptors (strychnine), GAMK-ov (bikuku-lpny or picrotoxin), dopamine (haloperidol), etc. can be an example of damages of brake processes of the second type. Mechanisms of presynaptic braking are similarly broken; in this case brake influence of the bombway terminating on presynaptic nerves drops out. If postsynaptic braking is broken — postsynaptic neurons are overstimulated; if presynaptic braking is broken — the stirred-up presynaptic device of secretion of the transmitter is overstimulated and effects of the last amplify. Brake mechanisms are less steady, than exciting and therefore in case of local nonspecific damage of these or those departments of c. N of page (e.g., disturbances of microcirculation, injury, etc.) first of all brake processes, as a rule, suffer that is followed by a disinhibition of the corresponding pre-and postsynaptic structures. It must be kept in mind also that any structure of c. the N of page exerts double impact on other educations: on one — exciting, on others — braking. Therefore at different damages of c. N of page (even in case of a direct injury and emergence of signs of loss of function of the damaged department) always take place of the phenomenon and rastormazhivannya, and hyperactivities of structures.
Oppression and loss of function can be also caused by several reasons. Morfol, defect of nervous tissue or a break of conduction paths or nervous trunks owing to any injury, a stroke, etc. cause paralyzes, according to central or a peripheral origin. Along with it funkts, insufficiency and even loss of functions can be result of activity hyperactive patol, the system causing patholologically the strengthened interfaced braking of others funkts, structures or fiziol, systems. Direct activation of the braking devices existing is possible and is normal. So, formation of the center patholologically of the strengthened excitement in departments of a reticular formation of a myelencephalon, to-rye normal cause the descending braking of spinal reflexes, involves deep suppression of these reflexes; the center of excitement in sonnogenny system causes patholologically the extended dream. Similar effects of deep braking are known at many forms of pathology where external manifestation of activity patol, systems are brake phenomena (a catatonia, a stupor, hysterical paralyzes, etc.). In a pathogeny of cerebral palsies, paraplegiya, at poliomiyelita, traumatic damages, ischemic strokes, etc. an important role is played by braking of intact neurons in the field of defeat. This braking can matter the guarding and compensatory mechanism limiting a zone of damage and preventing further damage of neurons. But it at the same time strengthens manifestation funkts, defect; at its removal to lay down. influences observe recovery of motive function in the corresponding volume. The similar phenomenon — so-called functional asinapsiya (N. I. G rashchenny, 1948) arises in the conditions of pathology of c. N of page, napr, at injuries. when neurons cease to react to irritation owing to disturbance of synoptic carrying out. This phenomenon — expression of a peculiar guarding braking.
Disturbance of the principle of duality of functional influences can happen at various forms of pathology. This phenomenon is caused by loss of one of functionally - antagonistic influences — excitement or braking — on this or that structure. At irritation of those departments of c. N of page, to-rye normal provide double (brake and exciting) influence on this structure, in the conditions of loss of one of these influences is accurately shown effect, to-ry normal can not be observed at all. This phenomenon of «unmasking» of the functional effect hidden normal especially clearly is expressed at disturbance of brake mechanisms: irritation of those departments of c. N of page, to-rye normal cause braking, can give exciting effect. The described phenomenon noted for the first time Ch. Sherrington allows to explain the phenomenon of the so-called perverted effects: «transformation» of braking into excitement at many types of pathology when brake mechanisms suffer (e.g., strengthening of the central pain syndromes and some other the syndromes which are characterized by a hyperactivity of systems at irritation of brain structures to-rye normal can cause the mixed or preferential brake effects).
Change of capacity of relay educations is observed at disturbance of brake mechanisms in system of their morfo-funktsponalny bonds. At patol, strengthening of brake control an exit of system «is locked» therefore the impulsation does not come to the subsequent structures of c. the N of page also arises funkts, the block. At insufficiency of brake mechanisms there comes simplification of carrying out an impulsation. This process is promoted considerably by the depolarization of a membrane of output neurons of relay educations weakening trace postsynaptic braking of these neurons; in such conditions orthodromic stimulation can be reproduced output neurons with unusually high frequency. Such phenomenon is observed, for example, at disturbance of brake processes in system of an efferent exit in a spinal cord. Increase in capacity of an exit of relay educations can lead to emergence of the syndromes which are characterized by a hyperactivity of nervous structures.
Populations of the neurons producing the excessive, not conforming to requirements of the moment flow of an impulsation can be called generators patholologically of the strengthened excitement (G. N. Kryzha-novsky). The main condition of their formation and activity is insufficiency of brake mechanisms in this population of neurons. This insufficiency can be primary — at effect of the substances which are selectively breaking brake processes (effect of a disinhibition), or secondary — at excessive, nekorrigiruyemy activation of neurons by various agents causing depolarization of a neyronalny membrane. Generators can forkhmirovatsya (or to be created in an experiment) in various departments of c. N of page. They are the direct pathogenetic mechanism of system pathology. Owing to insufficiency of brake mechanisms in population of the neurons forming such generator the last gets out of the system and integrative control of c. N of page that creates difficulties of fight against it. Replacement of the braking influences exciting at activation of the structures causing normal brake effect is for the same reason possible.
Two stages are characteristic of formation and activity of the generator. At the first stage excitation thresholds of neurons of the generator are still high and brake mechanisms are rather effective; at this stage the generator is activated by stimulation only of a certain modality, the corresponding specifics of this system. At the second stage when excitation thresholds of neurons of the generator are considerably reduced and brake mechanisms are insufficient, the generator can be excited by various, quite often accidental irritants, and also be activated nazavisimo from stimulation (so-called spontaneous paroxysms).
Formation of the generator patholologically of the strengthened excitement represents very complex process. Disturbance of brake processes leads to leveling initial funkts, properties of neurons, there is funkts, a homogenization of population of the neurons of the generator working as uniform funkts, a pool. At the same time there is funkts, a differentiation of neurons on groups depending on their epileptic properties. Neurons of the first group are leaders (microgenerators in the generator). Rather constant activity is characteristic of them; they make the critical weight necessary for maintenance of activity of the generator during the mezhpristupny periods, and «start» the generator during an attack, involving neurons of the second and third groups in process. At the same time neurons of the second group gain epileptic properties, same, as from neurons of the first group; neurons of the third group only participate generally patholologically the strengthened excitement. An important role is played by the strengthened positive (exponential) bonds, and also changes of the extra-and intraneyronalny environment, in particular the increased concentration of extracellular potassium, increase in an entrance to a cell of calcium ions, etc.
Features funkts, the organization and activity of generators patholologically of the strengthened excitement cause also features of course of the neuropathological syndromes which are characterized by a hyperactivity of systems, and in particular features of attacks, characteristic of these syndromes: selectivity (specificity) of provocative stimulation at early stages patol, process, ability of various irritants to provoke an attack and spontaneous paroxysms at late stages, strengthening of weight and duration of attacks together with strengthening of power of generators, character of attacks — tonic or phasic (acute, paroxysmal), etc.
Pathology of the system relations. To number of typical processes and phenomena of higher order, to-rye represent also transition to system pathology or are its expression, belong isteriozis, patol, a dominant, hyperactive determinant structure, patol, system and steady patol, a state.
Isteriozis (H is for the first time described. E. Vvedensky in 1912) represents rather permanent increase in excitability arising at a long tetaniza-tion of an esodic nerve: even weak force afferent irritations of other nerves can cause the strengthened reaction, at the same time the Reciprocal relations, as a rule, are not broken. Irritations of that nerve, to-ry was exposed to a tetani-zation, cause the weakened reaction. Isteriozis can arise also at long irritation of autonomic nerves. The mechanism of an iste-riozis consists in simplification of carrying out excitement on a poly-sinapticheskim to arches, increase in excitability of neurons and weakening of brake control. H. E. Vvedensky saw in this phenomenon looking alike symptoms of hysteria in this connection his isteriozi-catfish called. Isteriozis is close to the phenomenon of irritable weakness described by I. P. Pavlov. Signs of an iyeteriozis can be observed at those forms of pathology of N. of page, to-rye are connected with a hyperexcitability of the neyronalny device.
The dominant described by A. A. Ukhtomsky in 1923 — 1925 as the principle of the intercentral relations, is in what functionally active system is interfaced slows down activity of others cityy, i.e. only this reaction is possible at present. The dominant is the principle of the mezhsis-dark relations. When the dominating system or this or that center are excessively active, their braking influence on other systems (centers) can be also excessive that can lead to deep suppression of activity of these structures (centers) and disturbance of integrative activity of c. N of page. The inadequate, excessively strengthened braking influence of the center working at present or funkts, systems can be a sign of a pathological dominant. Patol, a dominant can play an important role in mechanisms and in pathogenetic structure of many forms of pathology of c. N of page, being clinically shown in the form of syndromes of suppression, loss, paresis, the general or partial block, etc.
It is necessary to emphasize that so-called internal signs of a dominant (a hyperexcitability, ability to accumulation of excitement, strengthening of activity and increase in level of excitement at the expense of various irritations from different sources, inertness of excitement — i.e. long preservation of excitement after activation) belong to properties of the excited population of neurons with reduced excitation thresholds, or the generator of excitement. Acquisition by such population of neurons of value of a dominant in the intersystem relations is defined by conditions of activity and a condition of other structures, with to-rymi it is functionally connected. The specified signs are shown especially clearly, than more hypererethism of neurons of the generator. These signs can be shown jointly or separately at different patol, processes in c. N of page. So, the congestive centers of excitement and patol, inertness of nervous processes, according to I. P. Pavlov, can be combined or independent patol, signs. The pathogenetic basis of the first is made by generators patholologically of the strengthened excitement. Mechanisms patol, inertness of nervous processes can be various, depending on what level of the nervous organization covers patol, process: it can be defined by the molecular membrane mechanisms changed by the neyronalny and system relations (reverberant bonds, self-excited system and intersystem contours, etc.).
Ultraboundary braking has special value at disorders of higher nervous activity (see). It arises at action extraordinary on the power or situational value of irritations that is promoted by astenisation and unfavorable conditions of activity of N. of page. Being a consequence patol, changes in a brain, it can have also guarding value, protecting a brain from overshot effects in the conditions of pathology of irritations.
The functional education in the central nervous system defining the nature of the activity of other parts activated by it systems and, thus, behavior of system in general can be called by hyperactive determinant structure or a determinant (G. N. Kryzhanovsky). Normal the determinant is a working part of the program device fiziol, systems; its activity and created by it funkts, parcel conform to requirements of the moment. The determinant as the principle of nervous activity reflects the intrasystem relations, it defines funkts, hierarchy and behavior of parts of this system. The concepts «determinant» and «dominant» do not exclude, and supplement each other and work combined, providing integrative activity of c. the N of page is normal: the possibility of implementation of reaction by this system is provided with the interfaced braking of other systems; achievement by this system of the programmed result is provided with the corresponding activation of its parts by determinant structure. In the conditions of pathology the hyperactive determinant structure produces excessively strengthened funkts, parcel, edges does not conform to requirements of the moment and is defined only by features of activity patol, determinants. Neyropatofizio a logical basis of hyperactive determinant structure, its working mechanism makes the generator patholologically of the strengthened excitement. The hyperactive structure playing a role of a determinant can arise in parts, different, but functionally important for this system, according to localization of the generator patholologically of the strengthened excitement. It does other parts of system and eventually all system hyperactive. Than more powerful is the hyperactive determinant structure, especially other parts of system are coordinated by it, especially activity of all system is rigidly determined and that to a lesser extent it gives in to correction.
The pathological system (according to G. N. Kryzhanovsky, 1980) represents peculiar funkts, the organization consisting of the same elements, as given fiziol, the system, but result of its activity has no adaptive character; moreover, this result can play a role of a direct pathogenic factor. Patol, system unlike a functional fiziol, system does not disappear on reaching result: reaction can continue vaguely long even if it does to an organism harm. Activity patol, systems does not correspond to either action of an irritant, or requirements of the moment and reflects only features of activity of hyperactive determinant structure and, therefore, property of the generator which is its cornerstone patholologically of the strengthened excitement. Patol, system has ability to further development due to involvement of new structures of c. N of page, increase in the sizes and power of the generator. And its resistance can increase in these cases to lay down. to influences. Along with it it suppresses others fiziol, systems (signs patol, dominants) and will disorganize integrative activity of a brain. Features of behavior patol, systems rather clearly are shown in a wedge, signs of the syndromes which are characterized by a hyperactivity of systems. Here pain syndromes of the central origin, different hyperkinesias, episindroma, persuasive states, a stereo-tshsht belong; various violent forms of behavior, etc.
Works And. P. Pavlov and his pupils the pathological temporary communication which is expressed that indifferent or even biologically useful irritations, being combined with patol is described. the effects caused by extraordinary irritants become starting incentives for a call of these effects or similar states. This form of pathology also is typical.
To category patol, systems can be carried also patol, a reflex, i.e. the reflex changed in such a way that its result has biologically negative value for an organism (see. Reflexes pathological ).
Syndromes of loss. Various patol, syndromes can be caused by also anatomic defect of c. N of page and loss of the corresponding functions. Extent of these disturbances depends on the amount of damage and on compensatory opportunities of an organism. P and that a genite of j1 chesk and I erased uk that r and with in d ro - m of loss happens very difficult since can include the phenomena of a disinhibition and hyper activation of those departments of c. N of page, to-rye are caused by formation of generators patholologically of the strengthened excitement from sets of the stirred-up neurons. Quite often secondary syndromes of a hyperactivity are the main part patol, process; they bring the greatest sufferings to the patient and demand special treatment (e.g., pains and muscular rigidity after strokes and damages of nek-ry departments back and a brain and so forth). The phenomenon of a cerebrate rigidity, vyzyvemy, across Sherring-tonu, section of a trunk of a brain between front and back chetverokholmiya or bandaging of the main brain arteries can be a pilot model of syndromes of the specified type. In these cases loss (oppression) of phases p chesk their reactions and hyper activation of the tonic device, a prevalence of a hyper tone of anti-gravitational muscles and as a result ex-tensor rigidity of extremities, the zaprokidyvany heads, etc. is observed.
At full section of a spinal cord the animal has a spinal shock consisting in deep oppression of spinal reactions. It is well-marked at mammals and is shown the more clearly, than the specific organization H. of page is higher. In mechanisms of spinal shock an essential role is played by loss of the descending tonic influences from a brain, necessary for maintenance normal funkts, ability (reactivity) of spinal structures. In addition, an important role, on - vidi-momu, the braking of spinal structures caused by activation of those educations in a spinal cord plays, to-rye normal exert the braking impact, but are under torkhmozny control from a brain. At loss of the descending brake control these educations become more active in this connection not only reflex reactions, but also own spinal avtomatizm representing periodically replaced excitement and braking of the centers of antagonistic muscles are oppressed. Such avtomatizm clearly come to light at late stages after section of a brain in connection with easing intra spinal that a rmozheniya. I put I spinal shock are weakened at influence of the substances breaking brake mechanisms and increasing excitability of neurons (konvulsant strychnine, a tetanin, etc.). Eventually reactivity of a distal part of a spinal cord changes and the chuv-St in and those increases.! no St detsent ra l from a bathtub x structures (under the law of denervation) to pharmakol, to substances. E.g., aminazine, to-ry normal renders the descending braking on a spinal cord through supraspinal departments, in the remote terms after section is capable to affect directly structures of a distal part of a brain.
Pain syndromes of the central origin belong to syndromes of a hyperactivity; in their pathogeny effects funkts can be of great importance, losses — loss of brake control of populations of the neurons entering into these or those departments of nociceptive system therefore these neurons are overstimulated and form the generators patholologically the strengthened excitement playing a role of the most general (typical) pathogenetic mechanism of the central pain syndromes. Loss of brake control can be caused by disturbance of local brake mechanisms in this kernel or damage of other structures of c. N of the page exerting the braking impact (e.g., loss of influences of the structures providing epikritichesky sensitivity involves a disinhibition of structures of protopathic sensitivity). Creation (in an experiment) generators patholologically of the strengthened excitement in back horns of a spinal cord, in a thalamus, in bodies having a tail, in kernels of a trifacial allowed to reproduce pain syndromes according to spinal, a thalamic and striatal origin and a syndrome of trigeminal neuralgia. A current of syndromes, features of their manifestations, including emergence of trigger (kurkovy) zones, distinctions in ability of different irritants to provoke an attack at different stages of process, emergence of spontaneous paroxysms, duration and character of attacks and other features are defined by properties of generators and the nature of their activity. Pain syndromes of a peripheral origin (at hron, an injury of nerves, neuromas and so forth) can get the central component in connection with formation of generators patholologically of the strengthened excitement in the relevant departments of c eventually. N of page iod influence patol, afferentation from the periphery (see Bol). Generators patholologically of the strengthened excitement can arise as well owing to primary excitement of nociceptive neurons. In an experiment formation of such generators and the corresponding pain syndromes can be carried out by means of the substances causing direct depolarization of neurons. Administration of the substances suppressing a hyperactivity (nek-ry antikonvulsant, napr, Finlepsinum and so forth), or local impact on area of generators brake mediators cause suppression of pain syndromes.
Stable morbid condition — a difficult complex patol, and compensatory processes in a brain; it is especially characteristic for hron, diseases (N. P. Bekhterev). One of features of this phenomenon which is also belonging to the class of the most typical forms of pathology is that compensatory mechanisms owing to the stability can become «rigid» links patol. states and to gain biologically negative value. Being fixed as an imprinting of memory, steady patol, the state can keep for a long time.
Disturbance of ratios of the main forms of activity of a nervous system. Normal N.'s activity page and its structures is carried out in the form of a combination zhestkozaprogrammirovan-ache also stochastic forms. In the conditions of pathology this unity is broken and patol, process can go in the area of dominance or a stochastic, or zhestkodeterminiro-bathing form of activity. As extreme expression of the first type of pathology disintegration of system, the centers or funkts, groups of neurons on independent subgroups or units can serve, to-rye gain the known autonomy. Expression of pathology of the second type are hyper synchronization of activity of the nervous elements, the rigid, not giving in to control activity of system causing inefficiency usual modulating inside - and the intersystem relations. Such type of activity is characteristic for patol, the system induced by hyperactive determinant structure.
Specific neurochemical changes. Neurons of c. N of page reside under the influence of various mediator systems. At the same time a certain balance of neurotransmitters causes a state fiziol, activity or rest (or braking) neuron. Any patol, process in c. the N of page is anyway connected with neurochemical, changes, in particular with disturbance of mediator influences. So, in an experiment it is shown that hyper activation of the dopamine device of kernels having a tail is the fundamental neurochemical unit of a syndrome of a stereotyped behavior, and hyper activation of the meso limbic dopamine device — a basis of psychosis-like states. It is supposed that similar changes take place at the person at nek-ry forms of schizophrenia; apply neuroleptics to its treatment, napr, the haloperidol, to-ry blocks dopamine receptors. At insufficiency of the dopamine device in kernels having a tail there is a parkinsonichesky syndrome. It can be a consequence of damage of a source of dopamine — neurons of black substance or (for the second time) medicamentous use of a haloperidol (at treatment of schizophrenia). Features of syndromes, their specificity and pathogenetic structure are various in case of damage of neurons of black substance and in case of damage of final links of dopamine system (kernels having a tail, kernels of a mesolimbic complex, a cerebral cortex, a hypothalamus and other structures).
At any form of pathology of c. N of page in patol, process are in a varying degree involved all mediator systems, but preferential suppression or activation any of them takes place. In mechanisms of development of a row fiziol, or patol, states the special role belongs to the neuropeptids which are developed in a brain. They take part in induction and modulation of processes of memory, a dream, an analgesia, fear, etc. Also the possibility of «transfer» by means of the neuro peptides emitted from a brain of sick animals, nek-ry forms of pathology or elements patol is shown. states and neuro pathological syndromes (asymmetry of a muscle tone of extremities, decrease in thresholds of a call of epileptic activity or its induction, elements of a vestibulopathy, etc.). Endogenous substances — the ligands tying opiate receptors in a brain (endorphines, enkephalins) emitted from a brain of donor animals — cause in animals recipients an analgesia (see Opiates endogenous). At the same time endorphines and enkephalins can cause both a catatonia, and the psychotic phenomena in this connection there is a question of their possible role in a pathogeny of schizophrenia. It is established that at nek-ry patients with schizophrenia Naloxonum, being the specific antagonist of endorphine, can stop hallucinations and other symptoms. It is shown that peptides of memory (the substance promoting processes of consolidation) can provide longer preservation of generators patholologically of the strengthened excitement in c. N of page. Detection in a brain of receptors to benzodiazepines allows to think of existence of the endogenous ligands rendering tranquilizing effect. Assume that the brain contains the substances having anti-epileptic activity. It is established that the niacinamide and inosine contacting benzodiazepine receptors in c. N of page, are capable to suppress nek-ry types of epileptic activity. The synthesized peptides also cause these or those patol, symptoms, an analgesia, a catatonia, modulation of processes of storing, duration of operation of generators or strengthening of their activity. At the same time there are data that not only neuropeptids, but also other substances of still not clear nature can also play a role of modulators of nervous activity. It is necessary to emphasize value of neuropeptids and other biologically active agents in mechanisms of recovery and treatment.
Disbolism in various formations of a nervous system. Various patol, N.'s conditions of page are followed by disbolism in it. So, at wet brain in fabrics it the ratio of ions changes: ion concentration of sodium increases and ion concentration of potassium decreases. Activity of the majority of oxidizing enzymes, except for a lactate dehydrogenase is broken. At disturbances of cerebral circulation, in particular at ischemia of a brain, the content of ATP in fabric decreases, and due to disturbance of processes of oxidation there is an accumulation milk to - you and carbonic acids that leads to acidosis — the size of intracellular pH decreases to 6,0. At a heart attack of a brain in an affected area ATP and kreatininfosfat disappear; at the same time there is also an accumulation of carbonic acid and milk to - you, inorganic phosphate, various acid metabolites, activity of ATP-ases, succinate - and lactate dehydrogenases, cytochrome oxydase almost completely disappears. Considerable biochemical changes are observed at epilepsy: activity of biopower processes decreases, there comes acidosis. At spasms aerobic exchange switches to anaerobic. Concentration at - aminobutyric to - you decreases. Disturbances of exchange processes in glial cells are followed by increase of concentration of extracellular potassium.
Due to genetically caused falloff of activity nek-ry, preferential lizosomalny, enzymes there are diseases, at to-rykh in nervous cells there is an excess accumulation of various products of exchange. So, Nimann's disease — Peak (deficit of enzyme of a sphingomyelinase) is characterized by accumulation sfingomiyelp-on, a disease Gosha (deficit of enzyme (5 glucosidases) — accumulation of glucocerebrosides, mukolipidoza (deficit of enzyme of a r-galactosidase) — GM1 - a ganglioside, metakhromatiche-Skye a leukodystrophy (deficit of enzyme of sulphatase) — sulfatides, a disease to the Pomp, or a glycogenosis like II (deficit of enzyme and - glucoside-zy) — a glycogen etc. Accumulation in nervous cells of GM2-raH-gliozida as a result of deficit of the enzyme of a geksozaminidaza consisting of isoenzymes And yes V. Defitsit of an isoenzyme is characteristic of a disease Teja — the Saxophone And leads to defeat only of N. page whereas in case of deficit of both isoenzymes also N. of page, and visceral bodies are surprised. At a multiple sclerosis there is a disagregation of a myelin of nerve fibrils, and this process probably begins acid proteinases of the main proteins of a myelin with hydrolysis. In the glial tumors (astrocytomas) which are most studied from the biochemical point of view activation of anaerobic glycolysis is observed. Activity of oxidizing enzymes is in tumors at the level characteristic of an unripe brain. At parkinsonism exchange of monoamines, in particular dopamine is broken.
Considerable disturbances of exchange are noted at various forms of psychoses, depressions, schizophrenia, and also at effect of various psychotropic substances.
Compensation of the broken functions
the Processes having compensatory value at damage of a nervous system are carried out at all levels of its organization. The intracellular processes connected with increase funkts loadings, have nonspecific character. The combined increase of a metabolic cost and power capacities of a cell, depression of structural genes and activation of the genetic device, increase of synthesis nucleinic to - t and proteins, strengthening of activity of fermental systems, etc. concern to them. An important role in life activity of neuron is played by intracellular regeneration, dynamic changes in localization and distribution density of dendritic spinules, to-rye can as S. A. Sarkisov (1964) showed, be reduced in the corresponding zones in the conditions of pathology and, on the contrary, again to arise and increase in number at funkts, loading, at elaboration of new bonds and so forth. Similar changes of synapses in the conditions of pathology, at changes funkts, loadings, formation of new bonds and the new intercentral relations were described by A. I. Strukov, S. K. Lapin (1956), and also H. N. Bogolepov (1975). All these plastic processes represent a peculiar form of a neuranagenesis, cells a cut are not capable to usual division, and make a basis of compensatory reorganizations and substitutions of the damaged structures. In implementation of reorganizations and formations of new mezhneyronalny bonds the important role belongs to a neuroglia (see). Special value in compensatory plastic processes has transsinaptichesky transport of trophic and biologically active agents.
Compensatory reorganizations are connected with change of intensity of secretion of mediators, edges is regulated not only orthodromic stimulation, but also feed-backs from presynaptic and postsynaptic membranes and postsynaptic neuron in general that is shown on the example of regulation of secretion of catecholamines.
Assume that in the specified processes cyclic nucleotides, neuropeptids and other biologically active agents shall play a part. Processes of compensatory reorganizations in N. of page, emergence of the new relations and stabilization of these reorganizations are very close to processes of memory; influences can influence them, to-rye are effective concerning formation of memory, in particular long-term memory.
Compensatory reorganizations as intrasystem, and intersystems-nye, are carried out thanks to mobilization of reserve opportunities of c. N of page, and brain in particular. The disinhibition funkts, structures and the hidden bonds at damages leads to hyper activation, character can have edges not only patol; this process can promote use of hidden, is normal not always of the active mechanisms providing overlapping and compensation funktsAI. This feature well illustrates the known, paradoxical at first sight so-called cross phrenic phenomenon: at a unilateral tractotomy there is a loss of function of an ipsilateralny half of a diaphragm, and after additional section of a phrenic nerve on the opposite side function of a phrenic nerve on the party of a tractotomy is recovered. It means that under the influence of the requirement of the moment (in this case essential an organism, important for life) there is an inclusion of the bonds which were not operating or slowed down earlier. Implementation of this phenomenon depends on specific and age features funkts, the organizations of c. N of page, and also from a time frame between the first and second operations. The analysis of a phenomenon shows that it is caused by inclusion of the invalid or ripening synapses. Existence of invalid synapses and their inclusion at damages of structures are shown in a cerebral cortex and other departments of c. N of page.
Compensatory reorganizations of systems or the mezhspstemny relations in N. the pages providing recovery to some extent to the broken function are carried out under the general integrative control of the highest departments of c. N of page. So, at recovery of motor functions of the spinal device an important role is played by its communication with a brain and integrity of a brain, especially bark (E. A. Asratyan). Processes of recovery and funkts, a reparation at damages or elimination of generators patholologically of the strengthened excitement are carried out at the different levels of c. N of page own mechanisms. E.g., receipt in the struck segments of the normal or stimulating afferentation (e.g., massage, the passive movements, electrostimulation) from the periphery is very important for normalization of motive function at suppression of the generator in system of an efferent exit in a spinal cord; lack of an afferentation can detain for a long time recovery of function. It is important to note that in the conditions of preservation of an afferentation normalization of motive function at elimination of the generator is late at dekortitsirovan-ny animals. The highest departments of c are of particular importance. and. page, and in particular a cerebral cortex, at recovery of function by a reeducation or training again after damages of these departments (an injury, an ischemic stroke, etc.).
At morfol, defects in various departments of N. of page performance of functions of the died elements is undertaken by the remained homologous or heterological structures. So, during removal of a part of the cortical end of the analyzer the remained educations fill funkts, defect; moreover, such result can be received at extensive defect thanks to inclusion in process of compensatory reorganizations of other sites of bark and even an opposite hemisphere. At damage of conduction paths and contacts with the innervated substrate the central parts of axons, strenuously regenerating, can form a branching of bombways. This phenomenon is rather effective on the periphery (at defeats of the neuromuscular device, recovery of function in the conditions of damage of a spinal cord and so forth) also has a certain value in reinnervatsion-ny mechanisms in the centers. Along with it it is known that the neurons of black substance taken from an embryo and replaced in bark of an animal recipient with the experimental parkinsonism caused log huts of ripa by telny chemical damage of black substance form axons, to-rye burgeon in kernels having a tail and contact with denervated neurons of these kernels that leads to elimination parkinsonichesky) a syndrome. Germinations of axons of this sort are noted at reconstructive changes and others mo-noaminergichesky, and also holii-ergichesk their neuro but in, about exhausted in Bjork-lunci researches et al. (1979). The received results speak about a taxis of nervous elements, surprising on the specificity and power, the obee-furnace in and yushchy with tr at a kta rno-f at N to tsio-nalny integrity and specificity fiziol, it is normal of systems also a possibility of compensatory reorganizations in the conditions of pathology. Examination and use of mechanisms of this phenomenon can make a recent trend in therapy of nervous diseases — organ and system engineering.
Process of elimination of disturbances in c. the N of page is carried out by a complex of mechanisms and has the nature of composite chain branching reaction. Depending on extent of elimination patol, process, stability of this effect and its clip, expressions subdivide recovery on clinically not complete and complete. During incomplete clinical recovery when patol, the syndrome is still shown by separate signs, various pathogenic factors can cause its aggravation or a recurrence. In an initial stage of clinically complete recovery the syndrome clinically is not shown any more, however elektrofiziol, ashes of an edov I can point to its existence. At this stage specific pathogenic agents are capable to provoke emergence of separate signs patol, process. So, after natural elimination of the epileptic center (clinically it is not shown any more) introduction to an experimental animal of any substances with eshtlepto-gene properties causes flash of the former center. In it, perhaps, the origins of a phenomenon of locus minoris resistentiae also consist (see) and value of the anamnesis for understanding of specific features of course patol, process. In 1937 A. D. Speransky described reproduction being patol, process under the influence of new pathogenic influence as a phenomenon of the second blow. In a closing stage of clinically complete recovery the pathogenic influences specific or nonspecific, cannot reproduce neither a syndrome in general, nor its components any more. At the same time in an organism, io-vidgshy, there is a structural trace, manifestation to-rogo under certain conditions can leave a mark on a picture of the subsequent patol, process.
Pathogenetic therapy shall be combined with therapy etiological, directed to elimination an ist in uyushchy a stalemate genno go fa who ra or the pathogenic conditions causing education patol, process and promoting its preservation or emergence again. At the same time at rational pathogenetic therapy patol, process can be suppressed, despite the continuing action etiol, factors. Rational pathogenetic therapy does not substitute, and stimulates processes of recovery and optimizes their implementation.
Efficiently suppression patol, process the method based on use funkts, antagonism fiziol, systems is. At irritation of so-called antino-tsitseptivny structures in c. N of page (central gray matter, dorsal kernel of a seam, nek-ry sites of a hypothalamus, etc.) there is an analgesia and suppression of pain syndromes. Prevention and suppression of epileptic activity are caused by electrostimulation of a caudal reticular kernel of the bridge, a worm, a cerebellum, kernels having a tail, etc. Creation in these structures of long-term generators of excitement provides steady preservation of the corresponding anti-effects. Similar long-term mechanisms probably take part in maintenance of the state of health. In this regard the problem of allocation from a brain of neurochemical equivalents of activation of «antisps-subjects» (peptides and other substances) in therapy and prevention is especially urgent for their use.
The method hron, electrostimulation and micropolarization of structures of a brain for fight against a steady patol, a state on the basis of mobilization fiziol is reasonable and almost tested. reserves of a brain. The methods of chres-skalpovy depolarization and other close ways applied for the purpose of normalization of the broken intercentral relations are approved. Methods of creation of artificial bonds in a brain and different types of a training are of considerable interest to destabilization and suppression patol, states.
The principle of complex specific pathogenetic therapy consists in the vaniye of the substances which are specifically influencing the interconnected pathogenetic links combined ispod zo. This principle provides fuller and pathogenetic adequate influence, true exponential effect of drugs and a possibility of their use in the reduced dosages.
The special type of treatment is made by restorative (recovery) therapy. So far it is limited generally to normalization of balance of mediators by their completion. Treatment of parkinsonism is based on it (introduction of L-DOFA, to-ry turns into dopamine and fills its shortage in the nigro-striatal device of c. N of page). Restorative therapy can receive and other ways of development in connection with interpretation of a role of various neuropeptids, hormones, prostaglandins and other biologically active agents in N.'s activity by the village. Real is an idea of implantation of embryonal nervous tissue for substitution of neurochemical defects of the damaged parts of c. N of page.
Experimental modeling — reproduction at animals patol, states and syndromes, to-rye arise at the person at N.'s defeats by the village. The pilot model cannot reproduce completely modelled form of pathology (see Model of a disease experimental). Animal different types can have various manifestation of the same syndrome. It is caused by distinctions of the structurally functional organization H. of page and ethological features of behavior of animals. Complexity of a problem of modeling neyropato l. syndromes of the person it is aggravated with that, as in a wedge, a picture, and in a pathogeny of these syndromes an essential role is played by social factor. All this defines philosophy of modeling: it shall be based on biological, i.e. neurophysiological and neurochemical, unambiguity of the reproduced syndromes, on the accounting of specific features of behavior of animals and on assessment corresponding a wedge, signs of model as symptoms equivalents. The general pathology of N. of page sets a task of such modeling neyropato l. syndromes, a cut, based on pathogenetic (neurophysiological and neurochemical) similarity of model and the modelled syndrome, opens mechanisms of the reproduced form of pathology, providing, thus, a possibility of development on this model of pathogenetic therapy; this therapy shall be both criterion of correctness of ideas of mechanisms of a syndrome, and an exit in a wedge, practice. Basic possibility of use of animal corresponding types for modeling neuro patol. syndromes at observance of the specified conditions is confirmed by practical criterion: by a possibility of treatment of homologous syndromes at animal different types the same drugs and selection during the testing for animals of means, to-rye further are applied in clinic.
The simplest way of reproduction of syndromes of loss consists in creation morfol, defect. More difficult way consists in reproduction of conditions for the strengthened interfaced braking of activity deep patholologically funkts, structures. Reproduction of the syndromes which are characterized by a hyperactivity of systems can be carried out by creation of generators patholologically of the strengthened excitement. It was succeeded to reproduce the central pain syndromes of various origin (spinal and thalamic bo the left syndromes, trigeminal neuralgia, model of stump neuralgias), a vestibulopathy, a generalized spinal myoclonia, muscular rigidity of a spinal origin, different types of epilepsy, a syndrome of a stereotyped behavior, a parkinsonichesky syndrome, a horeopodobny hyperkinesia, syndromes patholologically of the strengthened motivation, the dream patholologically extended, neurosis-like and psychosis-like states, etc.
Modeling of various forms of pathology of century of N of page by creation in its departments of generators of excitement (so-called diencephalic epilepsy, different vegetative crises, hyper - and hypotensions, tsentrogenny disturbances of a cordial rhythm, dystonia of internals, including went. - kish. path and bodies of a female genital, disturbance of secretion, change of intraocular pressure, etc.) means at the same time transition to area of pathology of regulation of internals (a disease of regulation).
Changes of a nervous system in the course of aging
Age changes of N. of page define the most important manifestations of aging of a complete human body (shifts in mental and behavioural reactions), decrease in intellectual and muscular working capacity, reproductive ability, adaptation by Wednesday, etc.
During the aging weight reduction of a brain, thinning of crinkles, expansion and deepening of furrows, expansion of system ventricular cis-ternalnoy is observed. There is a reduction of amount of neurons and substitution by their glial elements; in certain sites of a cerebral cortex loss of neurons can reach 25 — 45% (on otnoshe-them to their number at newborns). In spinal nodes of people 70 — 79-year age the quantity of nervous cells are 30,4% less, than at 40 — 49-year-old. At the same time in the vital centers of a myelencephalon decrease in amount of neurons is minimum. A natural and accurate sign of aging of nervous cells is accumulation of lipofuscin (a so-called pigment of aging), to-ry represents oxidate unsaturated fat to - t.
Microscopically reveal swelling of neurons and their shoots, homogenization of cytoplasm, shift and pycnosis of kernels, a cytolysis, tigro-liz etc.
At electronic microscopic examination find neurons with a hypertrophy of cellular organellas, symptoms of dystrophy (a kernel dense, perinuclear space with tanks and a time, mitochondrions without cristas, lysosomes with the broken membranes, etc.). In the course of aging along with destructive changes in N. of page there are adaptive shifts (a hypertrophy of separate neurons, increase in a surface of a kernel, quantity of kernels, etc.).
Aging of an organism is followed by essential changes of various functions H. of page. The average size of membrane potential of neurons (e.g., motor-neurons of a spinal cord, neurons of motive area of bark) significantly does not change with age. However at old animals neurons meet with the low size of membrane potential more often. There is a speed drop of spread of activation but to nerves (fig. 5), synoptic carrying out is slowed down. Essential age shifts arise in vegetative gangliya (fig. 6). In particular, changes of perception, processing and information transfer in nervous cells are connected with decrease in their lability. In experiments on animals it is shown that nerve centers, vegetative a ganglion, peripheral synapses at old animals cannot acquire high rhythms, transform them, quickly pass from one rhythm to another. Is of great importance in the mechanism of change of function of cells in an old age with and izh e and and e and to t and in but I would eat with t of 11 m r and and N<> y K+, KA +-ATF-azy, shifts in active transport of ions.
In the course of aging integrative activity of N. of page changes: are more slowly formed conditional r ef by l of EC with y, sn izh and it etsyatsya also about d in izh but St and force of the basic nervous processes, at a harm processes sosredoto a che-niya and concentration of attention, memory are barked; however weakening of mechanical storing at the same time is, as a rule, compensated by preservation and development of logical memory, increase in motivational factors, etc. Delay of an alpha rhythm, emergence or strengthening of slow fluctuations (a theta - and delta waves), decrease in a possibility of assimilation of the imposed rhythms is characteristic of EEG of elderly people.
During the aging subordinated influences of the highest departments of c are weakened. items of page on the lowest — grow thresholds kortiko-spinalyiy, retiku-lo-epinalnykh influences. These shifts are in many respects connected with weakening of brake process at the different levels H. of page — internal tormo-wives pya, reciprocal braking, rmo ziy influence 11 y retik ul I rno ii of a formation.
N.'s aging by the village cannot be considered as uniform fading of its functions. In the course of aging of a feather viomerno changes an electron of ZB ud an imost about t of affairs n ykh nervous structures and to gumo rat their sensitivity to ny factors. The great value in the mechanism of aging of an organism is attached to age changes of a hypothalamus. Uneven, multidirectional change of its separate kernels leads to a lack of coordination of functions of a hypothalamus and in this regard to decrease in reliability of regulation of a homeostasis. Weakening of nervous trophic influences, shifts in reaction to humoral factors lead to secondary age changes in fabrics (see. Old age, aging ).
Defeats of various levels and N.'s departments of page are caused by many reasons; vascular disorders, infections, intoxications, injuries, tumors, cooling etc. Prevalence of nervous diseases among the population is studied still far not fully. Judging by the available data, it considerably fluctuates in various areas, the countries and regions. In structure of the general incidence and mortality of the population respectively 8 — 10% fall to the share of nervous diseases and apprx. 12% • The general tendency to gradual reduction of a role of infections, intoxications, parasitic defeats, avitaminosis and a hyponutrient is noted (except for nek-ry developing countries). In the last half a century the role of vascular diseases and neuroinjuries increased.
Descriptions of individual diseases of N. of page — epilepsy, a stroke, concussion, meningitis — are available already in Hippocrates, K. Galen and Ibn-Sina's works. The first attempts to somehow group N.'s diseases of page belong to the second half 19 — the beginning is 20 century old. In 1949 nevrol, the commission at M3 of the USSR accepted classification of nervous diseases, on a cut these diseases were divided into 15 classes combining more than 130 forms. Since January 1, 1970 in the USSR the International statistical classification of diseases, injuries and causes of death combining apprx. 250 separate forms of diseases of N. of the page distributed on 17 classes (groups) is put into operation.
Basic groups of diseases of a nervous system. Vascular diseases nervous with and St of e of m y have great social and medical value. Treat them: acute disorders of cerebral circulation (hemorrhagic or ischemic strokes, crises) and hron, the vascular and brain insufficiency leading to distsirkulya-even encephalopathy. About 18 — 20% of all diseases of N. of page fall to their share. Etiology: atherosclerosis, hypertension and other forms of arterial hypertension, aneurism of vessels of a brain, intoxication, infection, pathology of heart, genetic predisposition etc. Development of acute disorders of cerebral circulation is caused by hl. obr. excessive fluctuations of the ABP, vasculomotor frustration (spasms, staza), defeat of a wall of vessels (hyalinosis, sclerous plaques), change of coagulating properties of blood.
The main a wedge, signs of acute disorders of cerebral circulation (see) — bystry, often sudden development of a disease, the expressed all-brain and focal symptomatology (a headache, nausea, vomiting, a hemiplegia, aphasia, etc.) depending on localization of the center and the nature of a stroke.
Infectious diseases of a nervous system are caused by implementation of pathogenic activators — viruses, microbes, spirochetes, nek-ry fungi and parasites. Falls to the share of neuro infections apprx. 5 — 7% of all diseases of N. of page. Most often are surprised a brain, the spinal cord and peripheral nerves are more rare (see. Arachnoiditis , Meningitis , Neuritis , Encephalitis ). Primary viral encephalitis — Russian, tick-borne, Japanese, West Nile and American mosquito, etc. is most widespread. Rather big group is still made by encephalitis with the unspecified activator (virus). Among the diseases capable to be complicated by development of secondary encephalitis — syphilis, rheumatism, malaria, a brucellosis, typhus, dysentery, flu, measles etc. The clinical picture depends on a form of a disease, type and pathogenicity of the activator. But there are signs, to a greater or lesser extent characteristic of all group of neuroinfections: emergence of all-brain, meningeal and focal symptoms after a prodrome against the background of temperature increase and other signs of a feverish state. The etiology of a disease in most cases can be specified after carrying out special virusol., bacterial, and serol, researches.
The panencephalitis, an amyotrophic side sclerosis (see), a myasthenia (see), a myelosyringosis enter into group of chronically progressing diseases of a nervous system multiple sclerosis (see), (see) etc. 1 — 2% of all diseases of N. of page falls to their share. The etiology and a pathogeny of the majority of these diseases are opened not completely. It is the most probable that genetic predisposition or the constitutional anomaly, being combined with action of various exogenous reasons (infections, a shortcoming or surplus of microelements etc.) leads to an abiotrophy — the lowered viability of this or that system of an organism. The clinical picture depends on a form of a disease though there are general signs: 1) the gradual beginning of a disease — is more often on average or advanced age; 2) relative systemacity of defeat — a cell of front horns and pyramidal ways (a side amyotrophic sclerosis), the neuromuscular device (myasthenia), etc.; 3) a long current with gradual increase of symptoms or remissions (an amyotrophic side sclerosis, Demyelinating diseases, a myasthenia, a myelosyringosis).
Hereditary diseases of a nervous system can be divided on chromosomal and genomic (see. Hereditary diseases). In development of the first the main role is played by aberation chromosomes, in development of the second — genomic mutations. 1% of all diseases of N. of page falls to their share on average. The most often found chromosomal diseases — a Down syndrome, Shereshevsky — Turner and Klaynfelter. Genomic diseases are subdivided on dominant and recessive, and on localization — into forms with preferential defeat neuromuscular (A myopathy, myatonias, mioplegiya, etc.) and nervous systems (a hepatolenticular degeneration, a chorea of Gentington, a myoclonus epilepsy, a spastic paraplegia, a family ataxy, etc.). The clinical picture depends on a form of a disease. Displays of weak-mindedness, infantilism, various somatic and endocrine frustration, for having genomic diseases — big selectivity of defeat are characteristic of the persons having chromosomal diseases (muscular weakness and atrophies, subcrustal or cerebellar disturbances, etc.) -
N.'s Defeats by the village can be caused to intoxications and — exogenous (methyl and alcohol, hypnotic drugs, etc.) and endogenous (owing to pathology of a liver, kidneys, a pancreas, etc.), avitaminosis (especially Vkh, And yes C), disturbances of food and metabolism (a galactosemia, a porphyria, etc.). Most often at the same time the scattered focal symptomatology with preferential involvement of peripheral nerves (see the Polyneuritis), a spinal cord (see the Myelipathy), a trunk and subcrustal nodes (see Encephalopathy) etc. is observed.
Tumors head and with and and N of N about about a brain are divided on primary (gliomas, arakhnoid-endotheliomas, neurinoma, adenomas of a hypophysis, a cranyopharyngioma, etc.) and secondary (metastasises of cancer or sarcoma). 1 — 2% of all diseases of N. of page falls to their share. Effects of growth of a tumor of a brain are shown by a combination of symptoms: all-brain (a headache, nausea, etc.), focal (paresis, aphasia, etc.) and dislocation (defeat of nek-ry cranial nerves, disorders of breath and cordial activity owing to a prelum of a brainstem). The clinical picture in many respects depends on localization of a tumor and features of its histogenesis. Gliomas have the most malignant current (medulloblastomas and spongioblastomas); ares-noidendoteliomy, neurinoma, cranyopharyngiomas are well limited and grow more slowly (see. Brain, tumors ).
Traumatic damages of a nervous system. About 6 — 8% of all diseases of a nervous system are the share of a share of an injury of a head and spinal cord. In the acute period it is shown by concussion, a bruise and a prelum of a brain, in remote — encephalopathy, an arachnoiditis, dientsefalezy, etc. Klin, the picture depends on a form of pathology: concussion is shown by disorders of consciousness, is general brain symptoms and retrograde amnesia, a bruise of a brain — accession of symptoms of focal defeat, a prelum of a brain owing to a traumatic hematoma — steady increase of all-brain and focal symptoms after a so-called light interval (see. Cherepnomozgovaya injury ).
Diseases of a peripheral nervous system are eurysynusic — radiculitis (see), plexitis (see), neuralgia (see), the neuritis, a polyneuritis making apprx. 40 — 45% of all diseases of N. of page; the most frequent form — lumbosacral radiculitis. Etiology: osteochondrosis of a backbone, infection, intoxication, cooling, injury, narrowness of bone channels etc. The clinical picture depends on a form of a disease and is shown most often by radicular pains and on peripheral type disorders of sensitivity, decrease in reflexes, paresis of separate muscles or muscular groups and vegetativnotrofichesky disturbances.
Damages of the autonomic nervous system can develop at systemic infections, injuries, tumors, vascular disorders. The most often found syndromes — diencephalic (see. Hypothalamic syndrome ), a neurangiosis, a Raynaud's disease (see Reynaud a disease), a truncitis (see), a solar plexitis (see), and also migraine (see), falls To their share 2 — 3% of all diseases of N. of page. Recurrence of a current, dominance of the phenomena of irritation, lack of the expressed focal symptoms and bent to irradiation and generalization of process are characteristic of pathology of century of N of page (see the Autonomic nervous system).
Functional diseases of a nervous system can be divided into the general neurosises (see), to the Crimea carry a neurasthenia, hysteria, a psychasthenia, and local forms — motive (a writer's cramp, spasms, stutter) and vegetative, and also neurosis-like states (a syndrome of neurosis). Falls to their share apprx. 15% of all diseases of N. of page. Neurosis is first of all a psychogenia, i.e. the investigation of a psychological overstrain and the microsocial conflicts (injustice, loss close, etc.). The passing, unsharply expressed frustration in the field of mentality, emotions and behavior in the absence of organic symptoms of defeat of N. of page are characteristic of neurosises. The nature of disturbance of activity of N. of page is distinguished on disturbances of the movement (see), sensitivity (see), vegetative functions (see the Autonomic nervous system). Nevrol, disturbances can be focal, i.e. connected with disorder of function of a certain department of a brain, and all-brain — changes of function of all brain as whole. At defeat of pyramidal system (see) there are paralyzes and paresis, to-rye are connected with a break of ways of any innervation of muscles in any their site from a front central crinkle to the muscle. Also violent, involuntary, excess or inexact movements in the absence of paralyzes or paresis can be observed. These disturbances are connected with pathology of the extrapyramidal system (see) providing thin regulation of motive acts. So, at defeat of striopallidal system there are hyperkinesias, i.e. the violent, excess movements, or, on the contrary, the general constraint (see Parkinsonism). Damage of a cerebellum (see) is followed by disturbances of balance and accuracy of purposive movements (see. Ataxy ). Motive disturbances can be also connected with disturbance of the scheme of the purposive automated movements owing to what autokinesias are complicated, despite the absence of paresis, paralyzes, hyperkinesias (see. Apraxia ).
Vegetative disturbances can be connected with defeat of structures of a brain, segmented vegetative educations, vegetative fibers, gangliyev and textures; displays of this pathology extremely of a polimorfna also include disorders of function of internals, vessels, secretions, thermal controls, a metabolism, function of endocrine system. Comparison of focal symptoms allows to define localization of defeat of N. of page.
All-brain frustration include disturbances of consciousness (see. Coma ), headache, vomiting, dizziness.
The special form of pathology of N. of page is made by mental disturbances with disorders of intelligence, thinking, memory, behavior, emotions, etc. (see. Mental diseases ).
Treatment of diseases of N. of page has nek-ry features. Vitamins, biogenic stimulators, neuroleptics, cholinolytics, anticonvulsants, hormones, coagulants, anticoagulants, antibiotics, and also physical methods of influence (LFK, physical therapy, solar and air bathtubs, bathings) are widely applied. Great success is achieved in treatment of disturbances of cerebral circulation, especially ischemic softenings, bacterial meningitis, the nek-ry hereditary and chronically progressing diseases (parkinsonism, the torsion dystonia, hepatocerebral dystrophy, a myasthenia), tumors of a brain, N.'s defeats by the village at osteochondrosis of a backbone. The role of surgical treatment increases; operations apply not only at tumors and traumatic hematomas, but also at some other diseases — aneurisms and angiomas of vessels of a brain, lateral hemorrhages and hemorrhages in a cerebellum, okklyuziruyushchy processes in carotid arteries, parkinsonism, hyperkinesias, a myasthenia, discogenic radiculitis, an epileptiform neuralgia.
The forecast depends on a type of a disease, localization and prevalence of defeat, age of patients, timeliness and the volume which is carried out to lay down. actions. In general it for the last decades significantly improved for the vast majority of diseases of N. of page E.g., the system of the step-by-step help to patients with disturbance of cerebral circulation (a special ambulance crew — chamber of an intensive care — a neurology unit — hospital for recovery treatment — health resort — dispensary observation) allows to reduce mortality, promotes recovery of working capacity.
Prevention is based on early diagnosis, sufficient treatment of easy and initial forms of defeat, mass recreational actions (sport, a hardening, tourism etc.).
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P. G. Kostiuk; Of H. Kryzhanovsky (stalemate. physical.), V. V. Kupriyanov (An., gist., embr.), Yu. S. Martynov, I. A. Skvortsov (a disease of a nervous system), M. G. Uzbekov (biochemistry, disbolism in various formations of a nervous system), V. V. Frolkis (the mister.).