From Big Medical Encyclopedia

MESENCEPHALON [mesencephalon (PNA, JNA, BNA)] — the forefront of a trunk of a brain located between the varoliyevy bridge and a diencephalon and consisting of a roof (tectum mesencephali) and legs of a brain (pedunculi cerebri). Legs of a brain are located on a ventral surface of S. m, the dorsal surface of S. of m is formed chetverokholmiy.

The comparative anatomy

the Difficult developmental character of structures of S. of m is defined as the general patterns of evolution brain (see), and ecological factors of formation of touch systems depending on biol. the importance of separate analyzers at these or those animals. The general pattern of complication of cortical formations of an end brain is shown, on the one hand, by increase in the cortical and trunk conduction bonds presented at

the level C. of m by legs of a brain and forming a so-called leg of a great brain at mammals, and with another — relative reduction of bonds of a plate of a roof (chetverokholmiya) with acoustical and visual receptors. The last comes in connection with a re-deployment of ground mass of projections of the corresponding analyzers from S.'s structures of m where they are located at the lowest vertebrata (including and the lowest mammals), in structures of a diencephalon (that is characteristic of the highest mammals, especially of primacies and the person). Influence of environmental factors in the greatest measure affects degree дифференцированное™ the lower and upper dvukholmiya depending on a role of hearing and sight in adaptation to it. So, e.g., at the majority of the land mammals leading a day life trunk educations are most developed visual analyzer (see); at the water and land mammals leading a nocturnalism structures are more developed acoustic analyzer (see).

At the lowest mammals the plate of a roof is presented by well-marked visual shares (lobi optici), to-rye at mammals form upper dvukholmy. Accessory upper a dvukholmiya to visual system and the layered nature of this education remain at all representatives of vertebrata. Posterolateral walls of a plate of a roof at the lowest vertebrata form to semi-circus-lyarnye the rollers located under visual shares. At mammals corresponds to these rollers lower dvukholmy, a cut together with upper dvukholmiy forms chetverokholmy. Lower dvukholmy is one of the centers of the acoustic analyzer. In addition to visual and acoustical, vestibular, proprioceptive and other projections are presented to chetverokholmiya that causes the correlation nature of this education for many vital functions, especially at the lowest vertebrata in connection with rather low extent of development and a differentiation of a neoncephalon. At vertebrata around S.'s water supply system of m the central gray matter (substantia grisea centralis) which is structural substrate of various vegetative functions is located. Under the central gray matter C. of m the reticular formation (formatio reticularis) presented at the lowest vertebrata diffuzno and differentiated on kernels at mammals lies.

The m which is the most differentiated by S.'s education at animals is the red kernel (nucleus ruber) which is accurately delimited from the next structures. At the highest mammals in a red kernel allocate two parts — the back, older small-celled part connected with the below-located structures of a trunk and with a cerebellum and a lobby macrocellular, phylogenetic newer, having bilateral ties with a cerebral cortex. Rather new S.'s education in the evolutionary plan of the m characteristic of mammals is black substance (substantia nigra) located over the basis of legs of a brain.

The anatomy and a microscopic structure

Anatomic borders of S. of m are conditional. The Zadnenizhny border passes from the place of escaping of the bridge of legs of a brain, posterosuperior from top to bottom — directly kzad from lower a dvukholmiya, front border ventrally — kzad from mastoidal bodies, and dorsalno — at the level of the epitalamichesky (back) commissure lying under an epiphysis. S.'s cavity of m is presented by a silviyevy water supply system (a water supply system of a brain, T.; aqueductus cerebri), connecting the third ventricle of a diencephalon to the fourth ventricle of a rhombencephalon (see. Ventricles of a brain ).

Legs of a brain leave upper parts of a varoliyev of the bridge (see the Bridge of a brain) in the form of two massive tyazhy and go, dispersing, in the corresponding cerebral hemispheres. The space, a cut is formed between legs, carries the name of an intercrural pole (fossa interpe-duncularis); it is closed by the so-called back made a hole substance (substantia perforata post.), small openings in Krom serve for passing of vessels from the basis of a brain to the educations which are in more thickly S. of m. Over legs of a brain it is located chetverokholmy. The cross furrow divides chetverokholmy into top and bottom hillocks, or hillocks (colliculi sup. et inf.), and the longitudinal furrow separates hillocks of one party from hillocks of the opposite side. In a venter of this furrow lies pinus (see), relating to to a diencephalon (see). Kpered and up white rollers depart from the lateral party of each of four hillocks (brachii colliculi sup. et inf.).

Fig. 1. Cross sections of a mesencephalon at the level of upper and lower hillocks are normal: on the right side of each drawing — a type of cross section on a tissue specimen, on left — the diagrammatic representation of anatomical structures, levels of cuts on a dorsolateral surface of a trunk of a brain are shown at the upper right: I \roof; II \tire; III \basis; IV \part of a diencephalon (medial cranked body); 1 — a red kernel; 2 — a leg of a brain; 3 — black substance; 4 — a medial cranked body; 5 — a medial loop; 6 — a back longitudinal bunch; 7 — kernels of a third cranial nerve; 8 — an upper hillock; 9 — silviyev a water supply system; 10 — decussation of upper cerebellar legs; 11 — a kernel of a block nerve; 12 — the lower hillock.

S.'s diameter of m (fig. 1) is conditionally divided into three parts — the basis [basis pedunculi (BNA), crus cerebri (PNA, JNA)], a tire (tegmentum) and a roof (tectum mesencephali). Sil-viyev a water supply system is surrounded with the central gray matter (substantia grisea centralis).

On the basis of S. the m of fiber and a kernel of the bridge disappear and release the fibers lying between them, to-rye gather, forming the basis of legs of a brain. Fibers in them are located in the following order: the central 3/5 legs are occupied with cortical and spinal and cortical and nuclear fibers; knutr from them lie frontal and bridge fibers, and knaruzh — parietal and temporal and occipital and pavements. On border of the basis and tire the medial loop caudally is located (lemniscus med.), and rostralno — black substance. The medial loop in the lower (caudal) parts of S. of m does not reach the centerline. The distance between both loops is busy with an intercrural kernel (nuci, interpeduncularis), legs of a mastoidal body (pedun-culi corporis mammillaris) and a bunch of a loop to a leg of a brain (fasciculus lemnisci ad pedunculum). Knaruzhi a medial loop reaches an outer surface of S. of m; slightly above it forms turn up and approaches close a lateral loop (lemniscus lat.), forming with it an obtuse angle.

Between the basis of a leg of a brain and a medial loop black substance (substantia nigra) is located. It has the form of a strip, wider in a middle part and narrowed on the ends. Black substance is divided into a dorsomedial compact part (pars compacta) formed by the cells rich with a pigment and ventromedialny — a mesh part (pars reticularis) containing myelin fibers in network to-rykh the big cells deprived of a pigment are interspersed. The interior of black substance is cut through by roots of a third cranial nerve (n. oculomotorius), and several knaruzha — fibers to mastoidal bodies. Cells of black substance of the considerable sizes, prodolgovata, multipolars-ny, are rich with dendrites, contain melanin, to-ry occupies the most part of cytoplasm in the form of gentle granularity and sometimes it is found in dendrites. Black substance has the following bonds: 1) with a cerebral cortex, hl. obr. with the central crinkles, back departments of frontal lobes; by means of centripetal and centrifugal fibers these fibers go via the internal capsule (capsula interna); 2) with a striate body (corpus striatum), and also with a lenticular loop (ansa lenticularis); 3) with a subthalamic kernel (nucleus subthalamicus); 4) with a thalamus (thalamus opticus); 5) with red kernels (nucll. rubri). Efferent pathways of black substance partially go through Epi - thalamic (back) commissure (commissura post.) on the opposite side, other part of fibers has the descending direction; ways to front a dvukholmiya, to area of a medial loop (lemniscus medialis), to a red kernel are established.

In S.'s tire of m in the corners formed by medial and lateral loops upper cerebellar legs lie, to-rye originate in kernels cerebellum (see) and in S. m form the decussation known under the name of decussation of Vernekinga (decussatio pedunculorum cerebellarium sup.). Rostralno in decussation two round educations — the red kernels covered with the fibers forming their capsule appear; partially these fibers reach a limit in these kernels, and partially — penetrate them and go to a thalamus further, to a cerebral cortex.

Kzadi from upper cerebellar legs and their decussation is in outside departments of a tire the central bunch of a tire of Bekhterev (fasciculus centralis tegmenti, s. fasciculus thalamorubrooli varis) going from a thalamus and from a red kernel to the lower olive kernel of a myelencephalon (see) to-rogo it around forms the capsule, and then terminates in its cells. Several knaruzha from a lateral loop lies a side bunch of a tire (fasciculus lat. tegmenti), directly kzad and several knutra from it - kernels are located reticular formation (see). On border with the central gray matter of a silviyev of a water supply system at the centerline there passes the back longitudinal bunch (fasciculus longitudinalis dorsalis, s. post.). The descending and ascending fibers are a part of this bunch. The descending fibers, having begun in Darkshevich's kernel and in an intermediate kernel, go down through a brain trunk in spinal cord (see) where come to an end in cells of front horns. A large amount of the fibers going from vestibular nuclei enters a bunch; vestibular fibers, entering a bunch, share on ascending and descending. The ascending fibers establish connection of vestibular nuclei with kernels the taking-away nerve (see), block nerve (see) and third cranial nerve (see) and opposite side. Through the descending fibers also connection with a motive kernel is established eleventh cranial nerve (see) and with a spinal cord (see). Directly near a back longitudinal bunch the pokryshechno-spinal way (tractus tectospinalis) lies, fibers to-rogo originate from cells of sublayers of upper hillocks a chetverokholmiya, partly from lower. During the escaping them fibers surround with arches the central gray matter and kzad from decussation of a krasnoyaderno-spinal way (Forel) form fontanovidny decussation of Meynert (decussatio tractuum tegmenti). Pokryshechno-bulbarnye fibers reach a limit in a trunk, in kernels of the nerves innervating muscles of an eyeglobe, and pokryshechno-spinal fibers — in cells of front horns of a spinal cord. In lower parts of S. of m, in gray matter, surrounding silviyev a water supply system, side kernels of a tire of a water supply system are located (nucll. laterales aqueducti cerebri), kernel and srednemozgovy way of a trifacial, kernel of a block nerve. In S.'s tire of m, at the level of decussation of Vernekinga, on the periphery the lateral loop relating to system of the acoustic analyzer lies; a part of its fibers goes to the lower hillocks a chetverokholmiya, a big part of fibers goes to a medial cranked body. S.'s roof of m makes chetverokholmy. The lower hillocks a chetverokholmiya where the lateral loop comes to an end, have the oval form. The acoustical fibers of a lateral loop entering kernels of the lower hillocks a chetverokholmiya form around them the fibrous capsule. Between both lower hillocks there pass komissuralny fibers. Lower dvukholmy is the center of compound instinctive acoustical reflexes. In it also other system of sensitive fibers — back pokryshechny a way (tractus spinotectalis) comes to an end. In rostral department of S. of m back dvukholmy is replaced to the lobbies differing from back more complex structure markedly. In it distinguish several layers. On a surface of a front hillock the layer of the I white matter (stratum zonale) lies, to-ry, as well as the layer of III (stratum opticum), is formed by the fibers from a visual tract which are reaching a limit in cells of a layer of II (stratum griseum superficiale); cells of a layer of II have the small sizes, their dendrites connect to visual fibers of layers of I and III, and the axon goes to a layer of VI. The layer of IV (stratum griseum medium) is formed by cells enough large sizes, axons to-rykh go to deep layers of a front hillock. The layer of V (stratum album medium, s. lemnisci) includes fibers from a lateral loop, and also fiber from a spinnopokryshechny bunch. All these fibers connect to dendrites of cells of a layer of IV. The layer of VI (stratum griseum profundum) is formed by the cells connected by fibers with cells of other layers of a front hillock; from its cells fibers begin, to the Crimea the fibers of a layer of VII (stratum album profundum) going from various gray layers upper, or front, a dvukholmiya join. All these fibers are a part of efferent fibers upper a dvukholmiya. They have the arc-shaped form, a part them goes to a tire of the party, others come over to the opposite side. These fibers are a part of the pokryshechno-spinal way going to a spinal cord and on the way of giving collaterals to a reticular formation and to a red kernel. Both upper a dvukholmiya are connected by komissuralny fibers. Upper dvukholmy is generally the center of instinctive visual reflexes.

In a tire, at the level of upper a dvukholmiya, between red kernels kernels of a third cranial nerve are located (nucll. n. oculomotorii), side, pair, macrocellular, knowing the movement of eyes and divided, in turn, into smaller groups of kernels corresponding to various muscles of an eye. Knutri and kzad from side kernels lies a pair small-celled additional kernel of Edinger — Vestfalya, or Yakubovich's kernel. It innervates through a ciliary node (gangl. ciliare) unstriated muscles of an eyeglobe (a sphincter of a pupil — m. sphincter pupillae) and a ciliary muscle (m. ciliaris). This kernel belongs to parasympathetic system.

The physiology

S. belongs to m to the multifunctional educations which are carrying out difficult reflex acts. The most important structure of S. of m is chetverokholmy, upper hillocks to-rogo provide the organization of approximate behavior on visual signals. Thanks to upper hillocks the coordination of consensual movements of eyeglobes necessary is carried out for solid vision (see), and a number of the vegetative reactions connected with sight (see): reductions of the unstriated muscles of an eyeglobe providing accommodation, pupillary tests on light, etc. On a surface of hillocks there is an exact somatotopichesky projection of a retina of an eye; each hillock receives fibers from a retina of both eyes, but it is more — from the opposite side. The majority of neurons of top coats of upper hillocks reacts to the movements of an object in any direction; apprx. 10% of neurons give reaction to the movement only in one direction (the directional and selection neurons). In sublayers of upper hillocks there are neurons, most active at spasmodic movement of an eye in a certain direction. In upper hillocks convergence of retinal and somatosensory afferentation is established. At the person these structures perform also function of distribution of the descending corticofugal influences.

The lower hillocks will organize orientation motor reactions on a sound: a nastorazhivaniye, turn of the head, etc. (see. Approximate and research reaction ). On cells of the lower hillocks the most part of fibers of a lateral loop switches. The neurons answering the low frequency of sound irritation are located in dorsolateral area lower a dvukholmiya whereas the neurons answering the high frequency of the irritating incentives are concentrated in rostroventralny area of the lower hillock. The tonotopichesky organization is characteristic of the lower hillocks; the functional organization of neurons of the lower hillocks allows to define the provision of a source of a sound in space and extent of its movement.

The red kernels located rostralno in a reticular formation S. in m closely connected with a cerebellum, vestibular nuclei basal kernels (see) and direct monosynaptic pathways with a motor zone of bark of cerebral hemispheres, in normal conditions slow down tonic anti-gravitational ekstensorny reactions of a spinal cord, holding them at the certain level. Functions of red kernels and a reticular formation (see) promote saving the normal provision of a body in space and participate in regulation poses (see). At an integrity of red kernels animals in response to irritation of skin or muscles have reactions of straightening. The cat with remote cerebral hemispheres, but with intact S. of m (a mezentsefalichesky animal), gets up if to lay it sideways. At S.'s section of m on a first line of back hillocks, i.e. kaudalny red kernels, at an animal develops cerebrate rigidity (see). Simultaneous removal of a cerebellum strengthens this state, arises so-called. opisthotonos (see). In recent years it is shown that S. of m at animals possesses an important role in the organization of the act of circulation: the irritation of certain sites of a mesencephalon causes the coordinate shagatelny movements in a cat.

The big role in implementation of motive functions and maintenance of a tone is played by black substance. Together with system of a pale sphere black substance performs statokinetic function, disturbance leads a cut to development of an amyostatic syndrome (see. Amyostatic symptom complex ). Cells of black substance at the person contain much melanin (see) — the pigment close to catecholamines, and a large amount of dopamine (see. Catecholamines ) — the predecessor of noradrenaline (see). Data of the last time on studying of various mediators of a brain indicate a big role of black substance along with the bluish place (locus coeruleus) in activity of noradrenergichesky systems. It is revealed that in the bluish place there is accumulation of noradrenergichesky neurons. The majority of axons of cells of black substance terminates on close located neurons of a reticular formation. From them the nigrostriarny dopaminergic ways going rostromedialno via the internal capsule and a striate body begin. Terminali of the axons leaving a striate body and terminating on cells of black substance contain a large number piperidic acid (see). Pry defeat of black substance at the person sharply expressed poverty of movements, constraint, maskoobraznsst persons, lack of the consensual movements accompanying the main motive act (akineziya) is observed. Other kernel of a reticular formation of S. of m is the intermediate, intersticial kernel (nucl. interstitialis). The electric irritation of this kernel causes turn of the head and an upper half of a trunk, rotary motions. This kernel receives the main afferentation from labyrinths of an inner ear and proprioretseptor of muscles, especially cervical.

In a reticular formation of S. of m the ground mass of fibers from more rostralno the located departments of a brain terminates. In a tire the fibers going to preoptichesky and septal areas, a basal part of a neoncephalon and basal kernels begin. From here the ground mass of fibers of the medial perednemozgovy bunch connecting structures departs limbic system (see) from S. of m. Characteristic property of reticular kernels — increase in their activity in response to any irritation going from the periphery and change of breath. In their structure the neurons answering change of content in blood of carbonic acid and oxygen are found. It is established that activity of a reticular formation of S. of m can be maintained a long time only by changes of internal environment of an organism. At decerebration at the level of upper hillocks the animal is capable to keep a long time normal respiration on condition of absolute rest. Neurons of this department of a brain answer with increase in activity at irritation of cutaneous, muscular, optic, acoustical and various visceral nerves. The reticular formation of S. of m is a part of the so-called facilitating system, edges transfers the ground mass of the ascending facilitating influences to a brain. In classical experiences of X. Meguna and J. Moruzz it is shown that S.'s tire of m and a basal part (hypothalamus) of a diencephalon render the longest and expressed activating effect on a cerebral cortex. Section of a trunk above these educations causes emergence of a continuous EEG-picture of a dream, and destruction of this area conducts to a deep coma. According to M. N. Livanov, a reticular formation, strengthening also it is long supporting a condition of activation, facilitates processes of irradiation of intracortical excitement. In the area C. of m a large amount of biologically active agents is revealed. So, in dorsomedial and caudal parts C. of m there is accumulation of serotonergic neurons; besides, there are accumulations of noradrenergichesky neurons. It is established that excitement of a reticular formation leads to activation a hypophysis - adrenal system that, in turn, causes increase in level of corticosteroids in blood, increase in contents them in adrenal glands, change of concentration of AKTG in a hypophysis, etc. Mobilization of all protective forces of an organism on the damaging influences results. A rostral part of a reticular formation of S. of m has hypersensitivity to adrenaline, but only at a certain level of thyritropic hormones in blood. The last is provided with activity of hypophysical adrenal system. Thus there are mutually activating neurohumoral cycles of excitement. Preferential participation of S. of m in motor reactions of a fruit and in implementation of a childbed is revealed. The active role of a fruit during the passing in patrimonial ways is connected with increase in activity of its S. of m. Also the role in the organization of a sentry reflex, providing an initial phase chetverokholmny, or start reflex — instant mobilization of all organism to vigorous activity at emergence of danger is attributed to a mesencephalon. At the same time all muscles are brought to ready condition to bystry action: hardening (stop reflex), start and a nastorazhivaniye (orientation response) and, at last, automatic (extramental) flight at big danger. This reaction can be caused by irritation of any modality, its reflexogenic zone includes practically all contact and distantny receptors. Thus, at the level of all structures of S. of m there is primary integration of somatic, vegetative, humoral irritants and composite unconditional reactions, functional systems — defensive, approximate, food, homeostatic, etc. form (see. Functional systems), with vegetative components and chemical specifics, characteristic of them. According to P. K. Anokhin, S. of m, its reticular formation, is one of the segmented structures exciting neurons of various departments of a brain, in particular bark, and creating behavior according to quality of initial excitement. Carry to group of the neurons which are a part of the activating reticular formation also neurons of the central gray matter (substantia grisea centralis), a cut has extensive bonds with hypothalamus (see) is also a component of limbic system. Believe that the central gray matter is also connected with regulation of the movement, there are data and on its participation in regulation of cycles dream (see). It is established that its destruction interferes with development of the visceral and behavioural reactions caused by irritation of a hypothalamus. In recent years the central gray matter is considered as the main anti-nociceptive structure — the irritation causes it an analgesia and increase in content in cerebrospinal liquid of endogenous opiates (see. Opiates endogenous ). The categories of neurons of a back horn of a spinal cord resulting from pain stimulation are suppressed at electrostimulation of the central gray matter. In the last a large number of opiate receptors and endogenous opiates (enkephalin and endorphine) is revealed. The irritation of the central gray matter suppresses the answers in a median kernel of a thalamus caused by pain stimulation. Feedforwards between these structures and the second somatosensory area of a cerebral cortex are morphologically established.

Methods of a research

at S.'s pathology of m apply To specification of the diagnosis ekhoentsefalografiya (see), with the help a cut reveal hydrocephaly, tumors; an angiography (see. Cerebral angiography ) for diagnosis of supraplacement and a kzada of a big vein of a brain and other vascular changes; a ventrikulografiya (see. Ventrikulografiya ) for detection of defects of filling of back departments of the third ventricle, hydrocephaly side and the third ventricles (in case of occlusion of a silviyev of a water supply system); an electroencephalography (especially with the caused acoustical potentials); a computer tomography of a brain (see. Tomography computer ), allowing to visualize patol. the center and to specify its character, prevalence.


Patol. the processes causing S.'s damage of m are various. A wedge, manifestations of defeats of S. of m depend on localization and size patol. the center in S. of m, and also from character of the basic patol. process in c. N of page (vascular, infectious, tumoral, traumatic). Various pathological processes in a head cavity can cause m, characteristic of S.'s defeats, a wedge, syndromes. The most frequent topiko-diagnostic characters of defeat of S. of m are alternating syndromes (see), various oculomotor disturbances, frustration consciousnesses (see) and dream, cerebrate rigidity (see). Distinguish Weber's syndrome from the alternating syndromes arising at hemilesion of S. of m — gomolateralny defeat of a third cranial nerve in combination with a contralateral hemiparesis or a hemiplegia, and sometimes and with a hemianaesthesia; Benedict's syndrome — gomola-teralny defeat of a third cranial nerve in combination with a contralateral hyperkinesia like a hemitremor, a hemochorea, a hemiballism, a choreoathetosis (see Hyperkinesias) or muscular rigidity (the syndrome is connected with destruction of a red kernel in that its part, to-ruyu penetrates a third cranial nerve); the lower red nucleus syndrome (develops owing to damage of a front cerebellar leg on the site from decussation of Vernekinga to a red kernel or defeat of the most red kernel) — gomolateralny defeat oculomotor, sometimes and a block nerve in combination with contralateral cerebellar symptoms — a gekhmiataksiya, dismetriy, adiadokhokine-zy. At defeat of oral departments of a red kernel the third cranial nerve can not suffer, in similar cases there is a so-called upper red nucleus syndrome — ataxy (see) in extremities on the opposite side, an intentsionny hemitremor, a choreoathetoid hyperkinesia, a hyperpathia. Alternating syndromes are often combined with other symptoms of defeat of S. of m. Sometimes at vascular defeats of S. of m there is a syndrome caused by simultaneous damage of an upper cerebellar leg, a spinotalamichesky way and a chetverokholmiya; at the same time are observed a choreiform or atetoidny hyperkinesia on the party of the center of defeat and frustration painful and temperature sensitivity (see) on the opposite side. At the same localization of process in connection with defeat of the central bunch of a tire there can be rhythmic myoclonia (see) soft palate, edge can extend to muscles of a throat, a throat, a bottom of a mouth, the person, eyeglobes.

Weber's syndrome is called a syndrome of the basis of S. of m, or a ventral syndrome of S. of m as it arises at defeat of ventromedialny department of the basis of a leg of a brain where there pass fibers of a third cranial nerve and a pyramidal way. Benedict's syndrome, an upper red nucleus syndrome, etc. carry to syndromes of a tire of S. of m, or intermediate syndromes of S. of m.

The oculomotor frustration caused by defeat of kernels III and IV cranial nerves are manifestation of a dorsal syndrome of S. of m. Oculomotor disturbances at S.'s defeat in m are caused by full or partial destruction of kernels of oculomotor and block nerves or damage of the specified nerves at their passing through S. in m, and also defeat of the system coordinating function of oculomotor muscles. Defeat of a kernel of a third cranial nerve is followed by paralysis or paresis of all outside muscles of an eyeglobe except for an outside straight line and an upper braid; note also ptosis (see) an upper eyelid, mydriasis (see) and areflexia of a pupil. It is often accompanied by anesthesia of a cornea due to involvement in process of close located kernel of a srednemozgovy way of a trifacial. Existence of this symptom allows to differentiate defeat of a kernel of a third cranial nerve from defeat of a trunk of a nerve. Defeat of a kernel of a block nerve leads to paralysis of an opposite upper oblique muscle of an eye and worsens the movements of an eye from top to bottom and several knaruzha; development of paresis on the party opposite to the struck kernel, is connected with the fact that fibers of a block nerve completely cross within S. of m.

At defeat of a back longitudinal bunch there can be a disturbance of consensual movements of eyes, and depending on proximity of the center of defeat to the kernel innervating this or that muscle of an eye there come the corresponding disturbances of consensual movements of eyes, and axes of eyeglobes stop being parallel that brings to diplopias (see). Sometimes in these cases it is noted monocular nystagmus (see) the taken-away eye. The oculomotor disturbances depending on defeat of a back longitudinal bunch designate as internuclear ophthalmoplegia (see). At defeat of pretektalny area (the predkryshechny field, T.) there is Parino's syndrome (see. Soared a syndrome ), to-ry also carry to dorsal syndromes of S. of m. At a syndrome of a water supply system of a brain the nystagmus joins oculomotor symptoms. Carry to dorsal syndromes of S. of m also Notnagel's symptom complex which is characterized by oculomotor frustration, a hearing disorder and a cerebellar ataxy, sometimes a choreiform hyperkinesia.

Disturbance of consciousness, a dream (see) often arises at extensive bilateral defeat of S. of m with involvement in process of the central gray matter and kernels of a reticular formation. Sleep disorders happen both in the form of a hypersomnia, and in the form of an insomniya (see. Dream, frustration of a dream ). The m a phenomenon of blinking of consciousness, i.e. fluctuation of its level from a lung is very characteristic of S.'s defeats devocalizations (see) to a deep sopor that is explained by disturbance of the ascending activating influence of a reticular formation. Sometimes there is an akinetic mutism which is characterized by what in the absence of paralyzes of the patient lies not movably with open eyes and the look of the patient only watching demonstrates that it in consciousness. Lack of active movements and the speech in such cases is caused by disturbance of motives to action and difficulty of motor integration. Amental, delirious, oneiric states, hypersomnias, and in nek-ry cases pedunku-lyarny hallucinosis — the peculiar, generally visual hallucinations of gipnagogichesky type developing during backfilling can be observed. Contents them is made by color moving figures of people and animals; the patient keeps the critical relation to hallucinations.

Patol. m quite often lead processes in S. to disturbance of muscular tone (see). Damage to black substance (usually in combination with defeat of a pale sphere) is caused by an akinetiko-rigid syndrome (see. Parkinsonism ); defeat of all diameter of S. of m kaudalny red kernels or functional dissociation at this level can lead it to development of a syndrome of a cerebrate rigidity (see). Depending on the nature of defeat the cerebrate rigidity happens resistant, arises sharply or pristupoobrazno. Sharp increase in a muscle tone leads to hyperextension of extremities. Sometimes hyperextension is observed only in the lower extremities, hands are in the provision of an inflection, muscles of a neck and a back are strained.

The isolated S.'s damages by m meet seldom that is explained by its deep arrangement in a head cavity. Generally it is gunshot wounds. Secondary damages of S. of m arise at its prelum owing to dislocations of a brain (see) or hemorrhages in S.'s parenchyma of m owing to disturbance of blood circulation and circulation of cerebrospinal liquid in a head cavity at to a craniocereberal injury (see), tumors, etc.

Fig. 2. Cross sections of a mesencephalon at the level of front a dvukholmiya at hemorrhage in the field of a red kernel (a) and a fibrillar astrocytoma in the field of a silviyev of a water supply system (6): and — native drug; — the gistotopografichesky cut painted on Shpilmeyera; sites of defeat are specified by shooters.

Most often vascular defeats of S. of m — hemorrhage (fig. 2, a) and heart attacks in the pool of branches basilar and back brain arteries, krovosnabzhayushchy S. of m develop (see. Cerebral circulation, pathology). S.'s heart attacks of m can be primary and secondary, caused trans-tentorial vklineniye at various supratentorial processes (an injury, a tumor, the extensive center of a necrosis or hemorrhage in a cerebral hemisphere). Inflammatory processes — encephalitis of various nature (see. Encephalitis ) also can strike S. with m and cause oculomotor frustration, a sleep disorder, a muscle tone, akinetiko-rigid and other syndromes. S.'s defeat m is possible at multiple sclerosis (see) that is expressed to hl. obr. oculomotor frustration and nystagmus. S.'s pathology of m is quite often caused by intracranial tumors: gliomas (astrocytomas, S.'s gliomatosis of m, pleksus-papilloma), tumors of strobiloid gland and its area — pinealomas (see), teratomas, etc. (see. Brain, tumors ). Wedge, a picture and symptomatology of defeats of S. of m at tumors depend on their localization and damage of these or those kernels and conduction paths of S. of m, degree of occlusion of a silviyev of a water supply system. Symptoms of defeats of S. of m at tumors can be resistant or remittiruyushchy that depends on whether the relevant structures of S. of m or a wedge are destroyed, the picture is caused by their hypostasis, a prelum. The prelum of a silviyev of a water supply system (fig. 2,6) can bring to hydrocephaly (see), to all-brain symptoms, developments of stagnation on an eyeground (see. Occlusal syndrome ) also makes heavier a clinical picture of defeats of S. of m.

Treatment at patol. processes in the area C. of m depends on an etiology of the disease which caused S.'s damage of m, its character and features of symptoms. At the dislocation of a brain which caused S.'s damage of m remove its cause (delete intracranial hematomas, foreign bodys), at S.'s compression of m make a puncture of cerebral cavities (see. Ventriculopuncture ), establish a temporary or constant ventrikulyarny drainage, cut cerebellar it is mashed (tentoriotomiya). Operational treatment at an injury and S.'s tumors of m is complicated in connection with its anatomic unavailability. With the advent of microsurgical technology of operation in the area C. of m began to make more often and with slightly best outcomes (see. Microsurgery ). Transkallezny access is most widespread (trepanation in the right occipitoparietal area with assignment from a crescent shoot of a cerebral hemisphere and a section of a corpus collosum). There are quick accesses to S. of m through a back cranial pole, through a right ventricle, consecutive use sub - and supratentorial accesses, etc.

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E. L. Golubeva (physical.), V. S. Kesarev, E. P. Kononova (An.), V. V. Lebedev, D. K. Lunev (pathology).