(sensi bili tas) — ability of an organism to perceive different irritations arriving from surrounding or internal environment and to answer them with the differentiated forms of reactions.
Plays a large role in adaptive activity of an organism h. Its research is important for assessment of a condition of functions of a nervous system. Besides, the problem of sensitivity is of great importance from the gnoseological point of view as by means of Ch. and the feelings arising on its basis subjective reflection of the objective world and processes of knowledge is carried out.
Physiology. Sensitivity as the specific differentiated form of response to action of irritants arose from more elementary property of the elementary organisms — irritability, or ability to the general undifferentiated reaction to irritations. This evolutionary principle was formulated by I. M. Sechenov.
Represents result of improvement of adaptive reactions of an organism h (see Adaptation) in the course of the evolutionary development happening owing to education special morfol. structures in certain body parts and selective increase in their ability of response to the corresponding (adequate) irritant. The most considerable development of Ch. is connected with emergence of specialized sensitive (touch) nervous structures — receptors (see) and difficult arranged sense bodys — sight (see), hearing (see), sense of smell (see), taste (see), the balances (see Balance of a body) perceiving and the transforming various forms of physical energy operating on them in a series of the afferent impulses which are transferred in c. the N of page the Highest form Ch. is feeling (see), i.e. ability to a subjective identification of properties of an irritant. Nek-ry more irregular shapes of Ch., napr, stereognozis (ability to learn by palpation a familiar subject blindly), arose upon transition of the person to the vertical way of movement which led to transformation of hands from body of a support in body of work. Development and Ch.'s complication happen not only in the course of phylogenesis, but also during life of each individual, in the course of his production activity. High perfection is reached, e.g., by Ch. at the persons occupied with organoleptic assessment of feedstuffs in connection with a training of a certain type of sensitivity. H
processes of reception (see), biol are the cornerstone. value to-rykh consists in perception of the irritations operating on an organism, their transformation in the processes of excitement (see) which are a source of the corresponding feelings (light, tactile, painful, etc.). However not everything that excites a receptor, is followed by subjectively experienced feeling. A certain intensity of irritation is necessary for emergence of feeling. So, e.g., to excite a separate light receptor of an eye (stick), one light quantum suffices, however the light feeling arises at action approximately of several light quantums. The minimum intensity of irritation capable to cause a feeling and called by a threshold of feeling, as a rule, is higher than Ch.'s threshold of a separate receptor. When coming from receptors to c. the N of page excitement is lower than a threshold of feeling, it does not cause the corresponding feeling, but can lead to certain reflex reactions of an organism (vascular, etc.)*.
Explanation fiziol. mechanisms Ch. gives the doctrine I. II. Pavlova about analyzers (see). Analyzers consist of peripheral departments — receptors, a conduction part — the afferent (touch) ways and cortical (central) departments presented by structures of a brain. As a result of activity of all links of the analyzer the thin analysis and synthesis is carried out (see. Afferent synthesis) the irritations operating on an organism. At the same time there is not only a passive transfer of an afferentation from receptors in the central department of the analyzer, and the complex process including the return, efferent, the regulation of sense perseption (see the Feed-back) which is carried out at all levels of passing of an afferent impulse vts. N of page (see Self-control of physiological functions).
Ch.'s type having the greatest value in life activity of this animal is provided in a brain with the big site of a cortical (central) part of the corresponding analyzer. For a mole, e.g., the most important type of Ch. is sense of smell; according to it more than a half of his brain occupies the central department of the olfactory analyzer. At birds the sense of equilibrium is of great importance, in this regard their greatest development of a cerebellum is noted. An essential part of a brain is borrowed from the person with the central department of the analyzer of skin and muscular and joint Ch. of hands and persons.
H constantly changes in development and life activity of an organism, adapting an organism for irritations of various intensity. H an eye, e.g., allows to see as night, and at bright solar lighting, i.e. at the brightness of light differing in billions of times. Such adaptive ability of an organism is provided with the difficult sum of the processes of adaptation of sensitivity proceeding both in receptors and in the central departments of the analyzer. During the loss of any type of Ch. compensatory development of other its types is observed. So, e.g., at the people who lost sight or hearing the high level of development of the skin P is, as a rule, noted.
Works of X. Meguna, J. Moruzzi, R. Granita, etc. it is established that any touch impulse which arose in the peripheral receptor device reaches a cerebral cortex not only on specific (see below) the carrying-out (lemnisko-vy) ways, but also on nonspecific systems of a reticular formation (see). Anatomic substrate for a flow of nonspecific afferent impulses are the spinoretikulyarny way and collaterals to cells of a reticular formation, to-rye give fibers of a spinotalamichesky way and a medial loop at the level of a brainstem. The reticular formation exerts also the descending regulating impact on process of an afferentation in sensitive ways through the activating and braking reticular systems (see. Functional systems). She participates also in selection of information going from the periphery to the highest departments of system Ch., passing one impulses and blocking others.
Classification. Depending on the place of influence of the corresponding irritations distinguish superficial (exteroceptive) and deep (proprioceptive) Ch. K of superficial Ch. refer painful, temperature (thermal and cold), tactile (tactile sense), voloskovy, feeling of humidity, etc., to deep — muscular sou - stavnuyu, vibration, pressure sense and feeling of weight. Separately allocate more difficult types of Ch.: localization, discrimination Ch., two-dimensional and space feeling, stereognozis, etc. The feelings arising at irritation of receptors of internals or walls of vessels belong to interotseggtivny Ch. (see. And nterotseption). All these types of Ch. concern to the general, or contact, Ch. connected with immediate effect of irritants on skin, mucous membranes, muscles, sinews, sheaves, joints, vessels. In addition to the general, allocate the special Ch. connected with function of sense bodys. Refer sight, hearing, sense of smell, taste to it. The first three types of special Ch. are connected with distantny receptors, i.e. the trailer nervous educations perceiving irritations at distance, the last — with contact receptors.
G. Ged suggested to divide Ch. into protopathic and I epikritiche-will hold down. Protopathic Ch., phylogenetic more ancient, inherent to more primitive organization of a nervous system, serves for perception of the feelings signaling about the danger menacing to an organism. Ch.'s types connected with perception of nocens nociceptive (Latin harmful belong to protopathic Ch.) the irritations menacing to an organism with destruction of fabrics or even death, napr, perception of strong, sharp pain stimulations, sharp temperature irritations, etc. Epikriticheskaya Ch., phylogenetic later it is not connected with perception of the damaging influences; she gives the chance to an organism to be guided in the environment, to perceive weak irritations, on to-rye an organism can answer with a so-called choice behavior — the certain motive act having character of any action. Refer to epikri-tichesky Ch. tactile, perception of low fluctuations of temperatures (from 27 to 35 °), feeling of localization of irritations, their discrimination (distinguishing) and muscular and joint feeling. Just as phylogenetic younger pyramidal system selectively brakes and regulates activity of more ancient motive systems, so epikritichesky Ch.'s system promotes to a certain extent self-organization of a flow of afferent impulses, braking the sensitive impulses which are carried out by system of the protopathic P. Loss or decrease in function of system of epikritichesky Ch. rastormazhivat functions of system of protopathic Ch. and does perception of nociceptive irritations unusually strong. In this case sharp pain and temperature stimulations are perceived as especially unpleasant; besides, they become more diffusion, diffuse and do not give in to exact localization. Such change of perception of nociceptive irritations at decrease in functions of epikritichesky system (thin irritations are perceived badly or are not perceived at all) is designated the term «hyperpathia».
Anatomy. The general Ch.'s system (afferent, touch, system) begins with receptors (see). Receptors subdivide into the exteroceptors located in skin and mucous membranes of an oral cavity, a nose and its adnexal bosoms, a conjunctiva a century and an eyeglobe (see Exteroception); the proprioceptors (see) located in muscles, sinews, ligaments, bones, joints; interoceptors (see. And a nterotseption), the bodies which are in internals, shank bores, blood vessels. On character of the perceived irritation distinguish mechanioreceptors (see), thermoreceptors (see), photoreceptors (see), chemoceptors (see), the receptors perceiving pressure (baroreceptors), and on character of the arising feeling — painful (nociceptors), tangoreceptors (see. Tactile analyzer), etc. Normal on 1 cm2 of skin on average contain 100 — 200 painful, apprx. 25 tactile, 12 — 15 cold and 1 — 2 thermal receptors.
Centripetal carrying out excitement comes from receptors on sensitive nerve fibrils, to-rye are peripheral shoots (dendrites) of cells of spinal nodes or their homologs in the head — a gasserov (trigeminal) node, a jugular node (an upper node of a vagus nerve), etc. Sensitive nerve fibrils divide into three groups: the fibers of group A covered with a thick coat of a myelin on the Crimea the afferent impulse is carried out with a speed of 12 — 120 m/s; the fibers of group B covered with a thin myelin cover, which are carrying out an impulse with a speed of 3 — 14 m/s; amyelenic (amyelinic) fibers C, on the Crimea the impulse is carried out with a speed of 1 — 2 m/s (for more details see. Nerve fibrils). The maximum frequency of fluctuations of action potential is noted at fibers of group A, smaller — at fibers of group B and minimum — at fibers of group C. Fibers of group A serve as conductors of tactile and deep sensitivity, but can carry out also impulses of pain stimulation; fibers of group B carry out pain and tactile stimulations; fibers of group C, as a rule, are conductors of pain stimulations.
All irritations perceived by receptors go to spinal nodes or nodes of cranial nerves, in to-rykh bodies of the first neurons of all types of sensitivity lie. Their axons as a part of roots of sensitive cranial nerves (see) enter a brain trunk or as a part of back roots of spinal nerves enter a spinal cord (see), forming in the latter case two groups of fibers.
The group of short fibers goes in back roots and, having entered a spinal cord, approaches cells of a back horn on the same party. From cells of a back horn (the second neuron) there are axons making a spinotalamichesky way. A part of fibers, having risen by 2 — 3 segments, passes through a lobby (white, T.) commissure also goes to a side cord of the opposite side of a spinal cord as a part of a lateral spinotalamichesky way up (tractus spinothalamicus lat.), the thalamus reaching specific veins-trolateralnykh of kernels (see). Other part of the fibers of a spinotalamichesky way which are carrying out the simplest types of tactile sensitivity (touch, voloskovy sensitivity, etc.), is located in a front cord of a spinal cord and makes a front spinotalamichesky way (tractus spinothalamicus ant.), also reaching a thalamus. From a thalamus to a sensitive zone of a cerebral cortex there are (through a back third of a back hip or leg of the internal capsule) axons of the third neurons of this way.
Group of the long fibers going in back roots and being also axons of sensitive neurons of spinal nodes, having entered a spinal cord, passes in a back cord of the same party (funiculus post.), forming a posterior pyramid (fasciculus gracilis) and a wedge-shaped bunch (fasciculus cuneatus). In these bunches they rise up, without being interrupted and without crossing to a myelencephalon where terminate in a thin kernel (nucleus gracilis) and a wedge-shaped kernel (nucleus cuneatus). The posterior pyramid of Gaulle contains the fibers which are carrying out Ch. from the lower half of a body, the wedge-shaped bunch of Burdakh contains the fibers which are carrying out Ch. from an upper half of a body. Long zadnekoreshkovy fibers of these bunches together with cells of spinal nodes, from to-rykh they depart, and their dendrites are the first peripheral neuron-mts of the big sensitive way going from proprioretseptor of a body to touch area of bark of big cerebral hemispheres. Fibers (axons) of the second neurons of this way, having begun in a myelencephalon from cells of thin and wedge-shaped kernels, come over to the opposite side and reach a vent-rolateralny kernel of a thalamus where bodies of the third neurons lie. The third neuron connects a ventrolateralny kernel of a thalamus to sensitive area of bark. On this three-neural way carrying out muscular and joint, vibration (it is partially carried out by side cords), difficult types of tactile, two-dimensional and space, discrimination
Ch., pressure sense, a stereognozi-s is carried out. This way does not cross in a spinal cord therefore Gaulle and Burdakh's bunches which are located in back cords carry out afferent impulses from receptors of the half of the same name of a body. Decussation is made by the axons of the second neurons forming a so-called medial loop (lemniscus med.). The medial loop consists of the fibers originating from thin and wedge-shaped kernels in a myelencephalon. Shoots of cells of these kernels cross, forming a so-called seam (raphe). This decussation of medial loops (decussatio lemniscorum) carries the name upper, or sensitive, decussation unlike the motive decussation of pyramids located in lower parts of a myelencephalon (see). After decussation in a seam of fiber of a medial loop go up and, having taken place in the tail (tire) of a va-roliyev of the bridge, in a tire of a mesencephalon (see), together with fibers of a spinotalamichesky bunch approach a ventrolateralny kernel of a thalamus. Fibers from a thin kernel approach the cells located lateralno, and from a wedge-shaped kernel — more medial groups of cells. Here also fibers from sensitive kernels of a trifacial arrive (see). From cells of a vent-rolateralny kernel of a thalamus sensitive ways pass through a back third of a back hip (a back leg, T.) the internal capsule, a radiate crown also terminate in bark posttsentrat a ny crinkle
(field 1, 2, 3) and an upper parietal segment (field 5 and 7) of cerebral hemispheres (see the Cerebral cortex).
Methods of a research of sensitivity divide on subjective and objective. Subjective methods are based on psikhofiziol. Ch.'s studying on character of the arising feeling. It is possible to characterize on space and temporary thresholds of feeling (see), to absolute thresholds of Ch., differential thresholds of Ch. h (see Esteziometriya).
Clinical trials of Ch. (see Obsaestivation of the patient, neurologic examination) it is necessary to conduct in heat, the room protected from noise. The patient shall lie blindly better to concentrate on perception and the analysis of the received feelings and also to exclude a possibility of identification of species of irritation by means of sight. More or less exact identification of frustration of Ch. is possible only at the adult. At small children it is possible to establish surely only painful Ch.'s safety on shout and the protective movements in response to pain stimulations. Investigate Ch. not for long not to cause exhaustion of the patient. It is necessary to avoid the inspiring expressions capable to provoke emergence at persons of a hysterical warehouse of psychogenic disorders of sensitivity at inspection.
Researches Ch. assume active participation of the patient. Results of a research depend on reaction of the patient, his attention, safety of consciousness, ability to be guided in the feelings and, at last, on desire to be exact and truthful in answers to the questions posed. Only at the qualified research Ch. on a certain scheme it is possible to receive necessary data for the nosological and topical diagnosis. Repeated researches by means of the receptions yet not known to the patient, and the subsequent comparison of the received results allow to objektivizirovat results of researches substantially.
Tactile Ch. (see Touch, the Tactile analyzer) is usually investigated a light touch to skin of the patient with a brush, piece of cotton wool, a soft piece of paper, etc.; painful — a prick of a pin or other sharp object; temperature — hiting at to skin the test tubes filled cool (not higher than 25 °) and more hotly (40 — 50 °) water. More precisely temperature Ch. can be investigated by means of a termoesteziometr (see Esteziometriya). In the absence of necessary conditions temperature Ch. is investigated approximately hiting at to a body of the patient metal (cold), rubber (warmer) part nevrol. hammer. After drawing the corresponding irritation of the patient shall characterize the feeling immediately.
The threshold characteristic of painful and tactile Ch. can be received at a research on Frey's method by means of the graduated set of bristles and hairs. Other special methods of a research Ch. are applied seldom. Practically it is not used at a research Ch. the method offered in 1885 by A. Gold-scheider — drawing pain stimulations by means of the terminal squeezing a fold of skin. This method gives the chance to reveal areas of a hyperalgesia and allows to establish the level of spinal defeat.
Discrimination Ch. — ability to separately perceive two identical irritations operating at the same time in two points of a body (see Touch) — investigate, using esteziometry — Weber's compasses. Normal two separate irritations on the palmar surface of fingers of a hand are perceived during removal of one from another on
2 mm; on a palmar surface of a brush it is distance reaches 6 — 10 mm, on a forearm and a dorsum of foot — 40 mm, and on a back and hips — 65 — 67 mm.
At painful, temperature, tactile Ch.'s research establish not only degree of safety of this or that type of Ch., but also ability investigated precisely to localize irritation (topognosis), edges it can be broken at nek-ry defeats of a nervous system.
Muscular and joint Ch.'s (kinesthesia) research is made in position of the patient lying blindly. The doctor makes unsharp passive bending, extension, assignment and reduction of fingers or all extremity in various joints. Investigated shall define the direction, volume, the nature of these movements. Begin a research with check of ability of the patient to distinguish the movements of fingers. Muscular and joint Ch.'s disturbance conducts to an ataxia — a sensitive ataxy (see). Use the device to objectification of data of a research of muscular and joint Ch. ki-nesteziometr.
Safety of pressure sense (baresthesia) is determined by ability of the patient to distinguish pressure from a light touch, and also to catch a difference in degree of the made pressure. The research is carried out by means of barestezio-meter — the spring device with a scale of intensity of pressure expressed in grams that allows to define a threshold of pressure sense and distinguishing of its difference. Normal the examinee distinguishes increase or reduction of pressure (on a hand) on V20 —:1/10 part of initial pressure. Researches of a baresthesia are conducted seldom since disturbance has no this appearance of Ch. of great semiologiche-sky value.
Vibration sensitivity (see) — ability to perceive vibration of a tuning fork, a leg to-rogo is put on the bone which is close to the surface of skin, usually investigate a tuning fork of low frequency (64 — 128 Hz).
Ability of recognition of two-dimensional irritations (two-dimensional and space feeling) is investigated, suggesting the patient to define at the closed eyes of figure, a letter and figure, to-rye investigating draws a pencil or a blunt end of a pin on skin of investigated.
At a research of stereognosti-chesky feeling (a stereognozis, or a stereognosis) to the patient, eyes to-rogo are closed, put various familiar objects on a palm: coin,
pencil, key, etc. Investigated shall, having felt a subject, to describe its form, to define a consistence, temperature, character of surfaces, to establish the approximate weight of a subject and its other qualities. Summing up all feelings connected with this subject, the patient shall connect them with image of a subject known to it and to call it. The difficult act of a stereognozis is connected with associative activity of a brain. Stereognostic Ch. is broken as at defeat of habit views of Ch. (a secondary astereognosis), and initially — at disorder of the highest cortical functions — a gnozisa (see Agnosia).
Voloskovy Ch. — the peculiar feeling arising during the carrying out by a soft brush, a piece of cotton wool by a pilar part of skin so that the irritating subject touched only hairs, without concerning the surface of skin. The research of voloskovy sensitivity in clinic is made seldom.
Objective methods of a research Ch. are necessary when in response to irritation of receptors there is no feeling. The greatest distribution in pilot studies was gained by methods of registration of electric potentials of receptors, the sensitive fibers departing from receptors or certain sites of a head and spinal cord. Registration of evoked potentials of various areas of a brain, the reactions arising in response to electric irritation of sensory nerves or adequate stimulation of receptors is widely used (see Bioelectric potential). In a crust, time the non-invasive technique of registration of pulse activity in sensory nerves of the person is developed.
Pathology of sensitivity can be shown by both quantitative, and qualitative changes. Reduction of intensity of feeling, i.e. Ch.'s decrease — a hypesthesia, or its full loss — anesthesia belongs to quantitative changes (see). According to Ch.'s type distinguish: hypalgesia (gipalgiya), analgesia (decrease or painful Ch.'s absence), thermohypoesthesia, thermoanesthesia (decrease or temperature Ch.'s absence), topogipesteziya, topoanesthesia (decrease or loss of ability of localization of irritation), astereognoziya, or astereognosis (loss of a stereognozis). Ch.'s increase connected with reduction of the threshold of perception of this or that irritation is called a true hyperesthesia. Refer disturbance (perversion) of perception of external irritations to high-quality frustration of Ch., napr, emergence of feeling of pain at cold irritation or at thermal (thermalgia); feeling of bigger size of the felt subject — a macroesthesia (e.g., the patient perceives the match put to it in a hand, as a stick); feeling of a set of objects instead of one (polyesthesia); feeling of pain, in addition to the place of a prick, in some other area (sin-algiya); feeling of irritation not in the place of its putting (alloesthesia); feeling of irritation in the symmetric site on the other hand (hallo-heyriya); inadequate perception of various irritations (dizeste-ziya), napr, perception of pain stimulation as thermal, tactile — as cold, etc. The special form of a qualitative change of Ch. is represented by a hyperpathia — a peculiar painful perception of various sharp irritations. Type the rpatiya differs from a true hyperesthesia (or giperalgiya) in the fact that at the last reduction of the threshold of perception of irritation takes place. At a hyperpathia, on the contrary, the threshold of perception of irritation (excitation threshold) is raised (slight irritations are perceived in the field of a hyperpathia less clearly, than normal, or at all are not perceived, and intensive irritations, especially nociceptive — as sharply painful, extremely unpleasant, painful). At the same time irritations are badly localized by the patient; their long after-effect is noted.
To Ch.'s frustration, not connected with any external influence, carry paresthesias (see) — various, often unusual, externally not motivated feelings, such as feeling of running of goosebumps, numbness, an odereveneniya of certain sites of skin, pain in roots of hair (trikhalgiya), feeling of humidity of skin, the movement of drops of liquid on it (hygroparesthesia) in the absence of the conditions stimulating feeling of humidity inherent to the healthy person (hygresthesia). Especially often various paresthesias observe at back to tabes (see) and other diseases of a nervous system, at to-rykh in about -
tsess back roots of a spinal cord are involved.
Carry to Ch.'s frustration also the pains accompanying nek-ry defeats of a nervous system (see Bol), including stump neuralgias in the amputated extremity (see the Phantom of amputated), a kauzalgiya (see), at a cut often observe a symptom of a gigromaniya (an inclination to wet), testimonial of value of a hygresthesia in the sum afferent to them - the pulsation making Ch. of the person.
At defeat of the receptor device the local hypesthesia caused by reduction of quantity of receptor points, and also change of threshold characteristics of different types of H can be observed. Increase in a threshold of painful and tactile Ch. can be very considerable (e.g., the corresponding minimum feelings appear only at irritation the largest bristles or Frey's hairs — No. 8, 9, 10). The hyperesthesia in the struck area is connected with the peripheral mechanism — patol. reduction of the threshold of excitability of the remained receptors and the central mechanism — increase in excitability of neurons of back horns of a spinal cord. Thereof the first adequate feelings appear at irritation the most gentle bristles from a set of hairs (No. 1, 2).
At defeat of a sensory nerve find two zones of disturbance: anesthesia in a zone of a car
of a nomny innervation only of this nerve, a hypesthesia with a hyperpathia in a zone of the mixed innervation (overlapping with zones of an innervation of other nerves); all types of Ch., but in various degree are broken (see Neuritis). Disturbance of all types of Ch. on distal type — in the form of long gloves on hands and a stocking standing is characteristic of multiple symmetric defeat of peripheral nerves of extremities (see the Polyneuritis) (fig. 1). And the hypesthesia is expressed to those more, than distalny the studied part of an extremity is located. Ch.'s decrease is combined with weakness of hands and legs (flaccid paralyzes or paresis of muscles), pains of different intensity, a hyperpathia and vegetative and trophic on rusheniye.
Defeat of back roots of spinal nerves causes Ch.'s disturbances in the corresponding dermatomas — zones of skin, shaped belts in a breast and a stomach and a form of longitudinal strips on extremities (fig. 2). The radicular hypesthesia (anesthesia) concerns all types of Ch., but not always to the same extent. If together with chuvstvitel-
Fig. 1. The diagrammatic representation of zones of disturbances of sensitivity (are shaded) at multiple symmetric defeat of peripheral nerves of extremities at a polyneuritis (and — the back view, 6 — an anterior aspect).
ny roots in process involved spinal nodes, sensitive frustration are combined from a gerpeticheskikhma by rashes in the corresponding zone of an innervation (see anglionit).
At cross damage of a spinal cord anesthesia is most often observed (or a hypesthesia) places of defeat are lower than all types of Ch., the zone of anesthesia is limited above to the circular line. This spinal (circular, or conduction) the type of frustration of Ch. is often combined with the central lower paraplegia and pelvic disturbances, making a so-called spinal syndrome (see Paralyses, paresis; Spinal cord). Level of anesthesia, as well as prevalence of paralyzes, is various at different levels of damage of a spinal cord. At localization patol. the center above a cervical thickening of a spinal cord there is an anesthesia of skin of a trunk, the lower and upper extremities, the upper bound passes a cut at the level Ssh_glgdermatomov; patol. the center in a Thlr-segment causes anesthesia, the top
ny border cuts is located at the level I of an edge, in TYU-segmen-te at the level of nipples, in Thix_x - a segment — at the level of a navel. At localization of process in a spinal cord below the specified levels anesthesia spreads to a lower part of a stomach, the lower extremities, skin of a crotch and generative organs.
Defeat of back cords of a spinal cord (Gaulle and Burdakh's bunches) frustration tactile, muscular and joint, vibration and other types of deep Ch. in hands and legs, followed by a sensitive ataxy, napr causes on the party damages, at back to tabes (see).
Defeat of a side cord on one party is followed by a hypesthesia (or anesthesia) painful and temperature Ch. on conduction type on side of a body opposite to the center, since level there is 2 — 3 segments below than the level of defeat. At cross defeat of a half of a spinal cord there is Broun-Sekar's syndrome (see Broun-Sekar a syndrome), at Krom muscular and joint Ch. on the party of the center of defeat is broken (owing to loss of function of a go-molateralny back cord), painful and temperature Ch. on the opposite side of a body disappears (owing to a break of a spinotalamichesky path in a side cord); tactile Ch. can be not broken since its conductors are not only in a back cord on the party of defeat, but also in a side cord opposite (not the victim) half
of a spinal cord. Higher than the level of disturbance of deep sensitivity often is found
Shai's not pain a zone of a radicular painful hyperesthesia.
Fig. 2. The scheme of a radicular sensitive innervation (above — the back view, below — an anterior aspect): not for
zones of an innervation of roots of cervical department of a spinal cord (Cu_vin) are shaded: pointed shading — zones of an innervation of roots of chest department of a spinal cord (ThI_xn) \are designated in black color zones of an innervation of roots of lumbar department of a spinal cord (Li_n-); zones of an innervation of roots of sacral department of a spinal cord (Si_in) are shaded.
Patol. the center in back horns of a spinal cord causes segmented frustration of Ch. on the party patol. process in the sites of skin innervated by the struck segments. Ch.'s frustration has at the same time the dissociated character: drop out only painful and temperature Ch. at safety tactile, and also muscular and joint and other types of the deep P. Ch.'s dissociation is connected with the fact that tactile stimulations are carried out to a brain not only on the spinotalamichesky path connected with nervous cells of back horns, but hl. obr. on system of back cords. The dissociated anesthesia is characteristic of a myelosyringosis (see), at a cut process usually begins with defeat of back horns of a spinal cord. Segmented frustration of Ch. extend at a myelosyringosis most often to hands and an upper part of a trunk, at the same time the .zona of disturbances has the «jackets» or «semi-jackets» form. The segmented dissociated anesthesia can spread only to an upper part of a trunk (a form of «vest»), and on Ch.'s hands remains undisturbed. This type of disturbances of Ch. can be observed also at intramedullary tumors and at vascular damages of a spinal cord.
At defeat of a lobby (white, T.) commissures of a spinal cord the dissociated anesthesia develops in several dermatomas on both parties, level the cut approximately corresponds to the level of localization patol. process.
At a research Ch. it must be kept in mind that skin of area of a neck and a shoulder girdle is provided with sensitive fibers from With, and _,^-сегментов, to an outer surface of a shoulder — from Cv, an outer surface of a forearm — from CVI, beam parties of a brush — from Cvn, the elbow party of a brush — from CV] II, inner surfaces of a forearm — from Th, a shoulder — Thn, the level of nipples — from Thv, the level of a navel. — from Thlx x, an inguinal fold — from Ll4 of a front surface of a hip (from top to down) — from Lj_iv, the anteriointernal surface of a shin — from LJV, the anteroexternal surface of a shin — from Lv, a back surface of a hip — from Lj_v, Sj_n, the posteroexternal surface of a shin — from
S, the posterointernal surface of a shin — from Sn, genitalias and the area surrounding them — from Sm_v (fig. 2).
At selective defeat of a kernel of a spinal way of a trifacial (see) in the field of a varoliyev of the bridge and a myelencephalon (generally at a syringobulbia) painful and temperature Ch.'s disturbances on the half of the face of the same name are observed. At the same time anesthesia (or a hypesthesia) spreads concentric strips around a mouth and a nose; medial and lateral zones of a skin innervation suffer unequally (see fig. 2 to St. Trifacial, t. 25, Art. 290).
At patol. the center in rostral departments of a tire of a varoliyev of the bridge (see the Bridge of a brain) there is Raymond's syndrome — Sestan (see. Alternating syndromes)'. a cerebellar ataxy on the party of the center and superficial Ch.'s hemianaesthesia on the opposite side of a body. The specified syndrome is usually connected with obstruction of an upper cerebellar artery.
Damage to one half of a myelencephalon is caused most often by emergence of a syndrome of Wallenberg — Zakharchenko (see. Alternating syndromes): gemigi-
a pesteziya on the side of a body opposite patol. to the center, and Ch.'s frustration on a face on the party of the center, i.e. an alternating ge-migipesteziya (see rice, 7 to St. Alternating syndromes, t. 1, Art. 318), edges is combined with paralysis of a soft palate, muscles of a throat and throat, Bernard's syndrome — Horner (see Bernard — of an orner a syndrome) and vestibular and cerebellar disturbances on the party of the center. The syndrome is connected with obstruction of a back lower cerebellar or vertebral artery, feeding side department of a myelencephalon.
Pathology of a thalamus can cause Dezherin's syndrome — Russia (see the Thalamus), at Krom there is a loss or decrease in all types
of Ch., a sensitive ataxy on an opposite half of a body (owing to deep defeat of muscular and joint Ch.), a counterlateral hemianopsia (see), the expressed hyperpathia, the central pains in all opposite patol. to the center to a half of a body — very intensive, diffusion, burning, resistant to use of analgesic means, various dizesteziya with an unpleasant affective component. Also the astereognosis is quite often noted (secondary). Ch.'s disturbances can be combined with gemigkharezy, usually without patol. reflexes.
In a back hip (a back leg, T.) the internal capsule conductors of all types Ch. for an opposite half of a body therefore defeat causes it a so-called kapsulyarny hemianaesthesia (or a gemi-gipeeteziya) are compactly located, for a cut big expressiveness of defeat in distal departments of extremities, especially on a hand is characteristic. Ch.'s disturbances are usually combined with a kapsulyarny hemiplegia (see) on the party opposite to the center since passes through a knee and a back hip of the internal capsule also a pyramidal way for an opposite half of a body.
The center in a radiate crown of a cerebral hemisphere also causes disturbance of all types of Ch. on the party opposite to the center, but in this case the gemigipesteziya never happens such full, as at defeat of the internal capsule as Ch. of one extremity always suffers much more another. This results from the fact that sensitive fibers in a radiate crown are located less compactly and occupy considerably the bigger volume of a cerebral hemisphere. Destruction of ground mass of the sensitive fibers innervating an upper extremity can be followed by defeat only of a small part of the fibers innervating the lower extremity and vice versa.
In a cerebral cortex sensitive fibers reach a limit with hl. obr. in a postcentral crinkle, in fields 1, 2, 3, i.e. in the main cortical sensitive zone. At the same time the top-most department of a crinkle the centers Ch. for a leg occupy, an average third — the centers Ch. for a half of a trunk and a hand and the lower third — a sensitive face zone. The postcentral crinkle is the highest the general Ch.'s synthesis analyzer for all opposite half of a body. The postcentral crinkle is considered a somatic sensitive zone I. Also additional cortical sensitive zones are described: cortical feeling
a telny zone II in the field of back department of an upper lip silviyevy (side, lateral) furrows and a zone III — on a medial surface of a cerebral hemisphere, a kzada from a postcentral crinkle. The general Ch.'s synthesis analyzer is the basic a postcentral crinkle, other zones play a less important role. In I and II cortical sensitive zones there are small sites connected not with opposite, and with the half of a body of the same name.
The center of damage to a postcentral crinkle causes a monoanesthesia (or a monohypesthesia) as a result of loss of function of a certain center Ch. As a symptom of irritation at these patients jacksonian touch attacks are quite often observed; partial paresthesias in a face, a hand or a leg usually short, proceeding without changes consciousnesses. A hypesthesia at cortical patol. the centers usually happens unstable, it is more expressed in distal departments of an extremity, n ri than we she chno-with at hundred vny feeling and vibration Ch. are broken more, than the superficial P. At paracentral (parasagittal-ache) localizations patol. process with destruction of an upper part of postcentral crinkles of both hemispheres of Ch. it can be broken on both groans. At damage of a cerebral cortex also nek-ry special more difficult types of Ch., such as recognition of a difference in intensity various, including skin suffer, irritations, exact definition of the space relations (topognoziya), is possible easing of ability to discrimination, two-dimensional and space Ch. and a stereognozisa. Primary, cortical astereognozis arises at defeats of hl. obr. parietal area.
Localization of the center of defeat of a nervous system defines character and the field of distribution of frustration of Ch.; besides, features of pathology of Ch. depend on an etiology of process and character of a basic disease.
Ch.'s frustration are often observed at various nosological forms, and at each form they can have the features, despite identical localization of defeat. Features of frustration of Ch. characteristic for defined a wedge, forms, are given at the description of separate nervous diseases and syndromes of defeat of a nervous system.
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