From Big Medical Encyclopedia

MECHANIORECEPTORS (grech, mechane the tool, the machine + receptors) — special sensitive nerve terminations (receptors) adapted for perception of mechanical irritations. Receptors of acoustic organs, perceptions of gravitation, a vestibular mechanism, cardiovascular system, internals, skin, a musculoskeletal system belong to M. Depending on localization and function a row M. received the independent name — e.g., receptors of a musculoskeletal system — proprioceptors (see), receptors of vessels — angiotseptor (see), the receptors perceiving vibration — vibroreceptors (see. Vibration sensitivity ) etc.

In any M. distinguish: the auxiliary device, mechanical characteristics to-rogo, as well as properties of surrounding fabrics provide features of carrying out a mechanical incentive (irritation) to a receptor; actually receptor substrate and related system of generation of the local electric phenomena (receptor potential); the structures responsible for generation of pulse activity, on a basis to-rykh c. the N of page receives data on character of the operating incentive (irritation). Idiosyncrasy of most of M. is their sensitivity to the direction of action of an irritant (directional sensitivity), edges can be caused both by features of a structure of auxiliary structures, and a structure of receptor (voloskovy) cells or nerve terminations (see). At one direction of action of an irritant in receptors there are a depolyarizatsionny potential and pulse activity, at another — the hyper polarizing potential interfering emergence of spontaneous pulse activity. Activity practically of all M. is under control of c. the N of page, edge has the regulating effect both the direct (nervous), and mediated (humoral) way that changes properties of auxiliary structures, receptor cells and afferent fibers departing from them (see. Nervous control of functions , Neurohumoral regulation ). The large role in many M.' activity is played by properties of the environment surrounding them. In liquid of channels of a snail of an inner ear high ion concentration of potassium (in an endolymph of the webby channel of a snail of the person it, e.g., in 30 times more, than in a blood plasma) and the reduced maintenance of ions of sodium is revealed. It is considered that strengthening of potassium ions in the environment and action of stationary hyperpolarization of M. promotes increase in their sensitivity.

Diagrammatic representation of a structure of voloskovo-ciliate (I) and aresnitchaty (II) mechanioreceptors of vertebrate animals; shooters designated the direction of neurohumoral regulation of activity of receptors: a somatic efferent innervation of elements of fabric (blood vessels, muscle fibers) — green shooters, the auxiliary device (a muscle of an outside ear, intrafusal fibers) — red shooters; a vegetative efferent innervation of elements of fabric, the auxiliary device and surrounding vessels — orange shooters; the humoral substances which are emitted from vessels — discontinuous shooters (red — exciting action, blue — brake action). Shooters in a synapse and afferent nerve fibril show the direction of processes of excitement (red) and braking (blue). External influence (incentive) — violet shooters.

Despite M.'s variety caused first of all by the features of their auxiliary structures connected with specifics of the innervated fabrics and bodies all of them can be subdivided into two main types. M of the first type possess the specialized voloskovo-ciliate structures (so-called voloskovo-ciliate M.) participating in acts of primary receptions (see). M of the second type are deprived of such educations (aresnitchaty M.). Perception of an irritant in them is carried out by directly mechanosensitive membrane of nerve termination. At vertebrate animals the voloskovo-ciliate complex is in a special voloskovy cell, edges bears own and receptor function. Voloskovo-resnitchatye M. have high sensitivity to action of an adequate mechanical irritant (e.g., M. of acoustic organs are capable to perceive so small shifts as shares of an angstrom). Regulation of their activity from c. the N of page is exclusively brake (tsvetn. fig., I). Aresnitchatye M. of vertebrata are less sensitive, and efferent influences on them preferential have the facilitating character or even exciting as, e.g., in case of muscle spindles (tsvetn. fig., II). Structural and funkts, M.'s variety causes big differences of the methods of their research using both psychophysical, and numerous modern analytical (Electrophysiologic, biophysical etc.) approaches.

M.'s pathology is very various and closely connected with pathology of fabrics and bodies, in to-rykh they are put, and is observed, e.g., at vibration disease (see), nek-ry types deafness (see), disorders of vestibular function (see. Vestibular symptom complex ), atherosclerotic defeats of cardiovascular system etc. At the same time patol, the changes affecting structures of the auxiliary device M. of the first type (voloskovo-ciliate M.) are reversible and can respond to treatment (e.g., at deterioration in activity of the sound carrying out structures of an acoustic organ). Damages of sobstvennoretseptiruyushchy structures have irreversible character and will not respond to treatment. Destructions of retseptiruyushchy structures and afferent nerve fibrils M. of the second type (aresnitchaty M.) are reversible and will respond to treatment, napr, recovery of tactile and proprioceptive sensitivity owing to the actions directed to regeneration of the damaged afferent conductors is possible.

See also Analyzers , Receptors .

Bibliography: Granite P. An electrophysiologic research of reception, the lane with English, M., 1957; it, Bases of regulation of movements, the lane with English, M., 1973; Ilyinsky O. B. Physiology of touch systems, p. 3. Physiology of mechanioreceptors, L., 1975; Physiology of touch systems, under the editorship of A.S. Batuyev, L., 1976.

O. B. Ilyinsky.