VESTIBULAR ANALYZER

From Big Medical Encyclopedia

VESTIBULAR ANALYZER (statokinetic) — the neurodynamic system which is carrying out perception and the analysis of information on situation and the movement of a body in space. Century and. consists of receptors, conduction paths (afferent and efferent), the intermediate centers and cortical department. Coming to c. and. pages impulses from vestibulo-and proprioretseptor cause emergence of vestibulo-motor (tonic), vestibulo-touch and vestibulo-vegetative reflexes.

Fig. Structurally functional organization of a vestibular analyzer. And (the upper drawing) — a schematic structure of a sensitive spot of a sack (utriculus or sacculus): 1 — gelatinous substance, in a cut voloskovy cells are submersed (4); 2 — a layer of otoliths; 3 — nerve fibrils; And (the lower drawing) — a schematic structure of a comb (crista ampullaris): 1 — gelatinous substance (cupula); 2 — voloskovy cells; 3 — nerve fibrils; 4 — a layer of foot cells. B — the scheme of the intra central relationship of a vestibular analyzer: I \bark of big hemispheres; II \level of a mesencephalon; III \reticular formation of a trunk; IV \cerebellum; V \level of a myelencephalon; VI \receptor of a vestibular analyzer; VII \level of a spinal cord. 1 — m. rectus lat.; 2 — m. rectus med.; 3 — n. abducens; 4 — nuci, vestibulares; 5 — tractus vestibulospinalis. B — a projection of a vestibular analyzer in bark of big parencephalons of the person (is shaded): 1 — on Ferstera; 2 — on Penfilda; 3 — on Kornkhubera.

V.'s receptors and. are located in a webby labyrinth inner ear (see). The labyrinth is presented by three semicircular channels and two sacks — utriculus and sacculus. Each channel leaves utriculus and, having spun two a third, again falls into it. On site confluences there is an expansion — an ampoule, and in the last — a comb (crista ampullris), a surface to-rogo is formed by a layer of voloskovy (sensornoepitelialny) cells; one of them have the form of a jug and others are localized on tops of cristas — a cylindrical form, are located in slopes; they are more organized and react, probably, to more local irritations. Those and other cells bear touch fibers on the free end, each of which represents the bunch consisting of 70 — 80 motionless stereocilias and one long mobile kinotsiliya on the periphery. The comb (fig., And, lower) is covered with the jellylike weight (cupula) adjoining closely a wall of an ampoule owing to what under the influence of shifts of an endolymph there is its shift. Receptors of sacks (macula) also consist of voloskovy cells of two types and a layer of foot cells. Over a touch epithelium the zhelatinopodobny membrane lies, in to-ruyu limy educations — otoliths are interspersed (fig., And, upper). Between otoliths and macula there is a narrow submembrane space, a cut gives the chance to an otolitovy membrane to slide on macula and to deform hairs of touch cells. Macula utriculi has the form of a concave oval spot of 3x1 in size — 5 X 2 mm and is located generally on a bottom, on a front and medial wall of utriculus. Macula sacculi lies on its medial wall, has the oval form (0,48 mm 2 ) also forms with macula utriculi a corner apprx. 90 ° (see. Otolitovy device ).

Natural irritants of V. and. the inertial shifts of an endolymph arising in semicircular channels at impact of rotary and Coriolis accelerations are (see. Acceleration ), and movement of otoliths (sliding is preferential, probably) rather voloskovy cells at rectilinear accelerations and the changed gravity. The arrangement of semicircular channels according to the planes of three-dimensional space allows receptors to react to the inertial forces arising practically at any movements of a body (active or passive), changes of size and a vector of gravitation.

From receptors of labyrinths primary nerve fibrils begin. The first neuron of the carrying-out system is in the vestibular ganglion lying in the depth of internal acoustical pass and representing accumulation of cells with two shoots. Long shoots of neuron make a vestibular nerve (see. Eighth cranial nerve ), bearing impulses to the second neurons — to a complex of the kernels in the bridge which are projected on lateral corners of a rhomboid pole (area vestibularis).

Vestibular fibers terminate generally on neurons in the central part of an upper kernel and a lateral kernel, in a posterolateral part of a medial kernel and in a back and medial part of the lower predoor kernel. A part of primary fibers, without being interrupted in kernels, goes to a cerebellum. In kernels secondary vestibular fibers originate and go as a part of a medial longitudinal bunch to motor neurons of oculomotor muscles and through a vestibulo-spinal path to the lower segments of a spinal cord.

In kernels of a reticular formation, apparently, upper, lateral and lower vestibular nuclei are projected. It is revealed that as a part of a vestibular nerve there pass the myelin fibers connected with a brain trunk and nek-ry kernels of a cerebellum; their main source — an intermediate kernel of a mesencephalon and a kernel of a back longitudinal bunch. From subcrustal educations the fibers of neurons of the third order which are reaching a limit in a cerebral cortex begin (fig., B).

Localization of cortical department of V. and. it is studied generally on cats by registration of evoked potentials. V.'s studying and. shows the person that cortical department of V. and. includes the field 21 according to K. Brodmann, an upper parietal segment according to O. Ferster (1936), bark of an upper temporal crinkle according to U. Penfildu (1957) and a postcentral crinkle on Kornkhubera (fig., In).

Afferent ways from vestibular receptors to bark are studied insufficiently.

It is important that on neurons of vestibular nuclei of the intermediate centers and in a cortical vestibular zone convergence of the impulses coming on various afferent fibers is carried out.

Numerous afferent and efferent bonds of V. of ampere-second various formations of c. and. the page are promoted by generalizations of effect of vestibular irritations. At high-organized animals and the person the space analysis is supplemented visual, proprioceptive, tactile, acoustical with analyzers at the predominating role of a cerebral cortex as integrator of an afferent impulsation. At deficit of touch information or at excessive vestibular irritations the vestibulo-touch reaction which is expressed in loss of dimensional orientation (developing of dizziness, illusory feelings) is possible.

At V.'s overexcitation and. there is a complex of the vestibulo-vegetative frustration which are expressed increase in a tone, hl. obr. parasympathetic nervous system: an urezheniye of pulse, lowering of blood pressure, changes of an ECG, narrowing of a pupil, strengthening of sweating, a vermicular movement went. - kish. path, etc. An essential role in an origin of vegetative frustration is played by a reticular formation of a brain trunk, about a cut vestibular nuclei have close structurally functional relationship. Besides, it is necessary to consider close ties of various kernels of V. of ampere-second internals (V. S. Raytses, A. M. Dutov, 1971). Vestibulo-vegetativnye reflexes can make a basis of a symptom complex of a disease of movement.

Methods of assessment of a functional condition of V. and. are based on the analysis of the reactions caused by the adequate dosed irritations. For this purpose there are special rotating chairs, centrifuges, installations imitating the lowered support, elevators. Also use of inadequate irritants practices (electric current, a caloric method — see. Vestibulometriya ). By repeated impacts on V. and. accustoming to irritants, or a training is reached (see. Vestibular training ), the physiological sense a cut comes down to decrease in thresholds of vestibulo-spinal reflexes and braking of touch and vegetative manifestations. It is possible that the pathogenetic basis of accustoming is made by other distributional pattern of excitement in a cerebral cortex and change cortical nodkorkovykh relationship. Century and. functions on the basis of close interaction with other systems of a brain and analyzers: cerebellum, striopallidal system, visual analyzer etc.

V.'s studying and. is of particular importance in practice of space exploration when as a result of influence of zero gravity and disturbance of certain types of sensitivity the conditions which are temporarily changing physiological properties of all analyzers defining position of a body in space are created.

See also Vestibular reactions .

Biophysical mechanisms of orientation information

For orientation in relation to gravitational field of Earth animals and the person have the receptor of gravitation constructed by the same principle — the sensor of position of a body. It is characterized by existence of the otolitovy device and cupula in a vestibular mechanism at vertebrata and the person and statocysts at invertebrates. Otoliths and cupula biophysical are «the trial weight». Receptor cells directly do not perceive gravitation. But any deviation in position of a body (linear and angular accelerations) is followed by the shift of trial weight and emergence of forces which cause excitement of the corresponding groups of receptor cells.

The receptor of gravitation of animals and the person always functions according to the same scheme, edges are included by three basic elements. The first — the mentioned trial weight; the second — the capable educations, sensitive to a deviation departing from top of receptor cells (a kinotsiliya and a stereocilia); the third element — the receptor cell estimating changes of sensitive educations and transferring in coded form information of c. N of page. Thanks to a special arrangement of sensitive educations at top of receptor cells at the movement of trial weight one cells are excited, others are braked. The structural and functional organization of a receptor of gravitation allows c. and. to determine by page orientation and to carry out installation of a body of animals and the person.

Dysfunction of a vestibular analyzer at beam influence. Sensitivity and V.'s reactivity and. in the conditions of acute exposition of an organism in various doses are investigated during the use of an adequate irritant (angular acceleration and Coriolis's acceleration). It is established that changes in function of a labyrinth are noted already at doses 50 — 100 I am glad. At these doses, as a rule, during the first hours on - hardly radiations excitability of the analyzer increases. Radiation in high doses (500 is also more glad) leads to considerable initial oppression of function of a labyrinth that is expressed in decrease in excitability and V.'s reactivity and. At action of an irritant of bigger force paradoxical and ultraparadoxical reactions develop. In 5 and more hours after radiation there is a normalization of activity of the analyzer. In conditions hron, radiations of an organism of animals within 3 — 6 years at a total dose 50 year is glad / function of a vestibular analyzer significantly is not broken, responses are adequate to the size of the applied irritant; similar results were received also in clinic.

In experiments with local radiation of a stomach, a front part of the head or only a brain it was shown that in emergence of functional disturbances from V. and. the large role is played by the so-called reflected effects. Radiation of peripheral parts of a body also leads to the mediated action of ionizing radiation on V. and., what is expressed in oppression of its activity.

Using the recommended prophylactics of a radial illness (see. Radioprotectors ), it is possible to weaken functional disturbances from V. and.

On the basis of the conducted kliniko-pilot studies the conclusion is drawn that under special conditions of the combined radiation effect and various physical. environmental factors (vibration, noise, etc.) perhaps interfaced increase in reactivity of V. and.

Dysfunction of V. and. at its radiation it can be observed at radiation of a middle ear in the therapeutic purposes, at working in certain professional conditions (e.g., radiologists), and also at astronauts at long space flights.

Dysfunction of a vestibular analyzer at other morbid conditions — see. Vestibular symptom complex , Labyrinthitis , Labyrinthopathy , Menyera disease , Motion desease .


Bibliography: Vinnikov Ya. A. Cytologic and molecular bases of reception, L., 1971, bibliogr.; About r silt and d z E. I. Cortical mechanisms of vestibular function, Usp. sovr, biol., t. 70, century 1, page 65, 1970, bibliogr.; Grigoriev Yu. G., F and r e r Yu. V. and Volokhov N. A. Vestibular reactions (Methods of a research and influence of various environmental factors), M., 1970, bibliogr.; To at r and sh in and l and A.E.I Babiyak V. I. Physiological functions of vestibular system, L., 19 75, bibliogr.; Ying V. V. steam of and d river. Sketches on space physiology, M., 1967, bibliogr.; Razumeev A. N. and A. A Thorns. Nervous mechanisms of vestibular reactions, M., 1969, bibliogr.; A receptor of gravitation, evolution of the structural, cytochemical and functional organization, under the editorship of V. N. Chernigovsky, L., 1971, bibliogr.; Hilov K. L. Cerebral cortex as a vestibular analyzer, M. — L., 1952, bibliogr.; it, Function of an organ of equilibrium and disease of movement, L., 1969, bibliogr.; Zimmerman G. S. Ear and brain, M., 19 74; Handbook of sensory physiology, ed. by H. Autrum a. o., v. 1, V. a. o., 1971; P e n f i e 1 d W. Vestibular sensation and the cerebral cortex, Ann. Otol. (St. Louis), v. 66, p. 691, 1957.

F. P. Vedyaev, M. D. Yemelyanov. Ya. A. Vinnikov, K. A. Koychev (biophysical.), Yu. G. Grigoriev (I am glad.)

Яндекс.Метрика