From Big Medical Encyclopedia

EXTEROCEPTION (Latin exter outside, external + [re] of ceptio acceptance) — process of perception and processing by an organism of the irritations arriving from the environment; it is carried out by specialized sensitive educations — exteroceptors. By means of exteroceptors light, sound, tactile, thermal, flavoring and olfactory stimulations are perceived (see Taste, Sight, Sense of smell, Touch, Hearing).

Perception by an organism of objects and the phenomena of the world around is connected with exteroception. Unlike interoceptors (see Interoception), the irritation to-rykh does not lead to formation of accurate feelings (see), the irritation of exteroceptors finally causes formation of accurate figurative perceptions (feelings). Switching off of exteroceptors (experimental or traumatic) not only reduces adaptive opportunities of an organism, but also reduces its general tone (see).

AA. includes primary processes of interaction of an external irritant with a sensitive membrane of the receptor device leading to emergence of specific transformational processes and generation of local electric potentials which mechanisms, apparently, are similar for various groups of receptors.

Irrespective of functional specialization all exteroceptors can be divided into two groups: primary feeling (the sensitive terminations of touch, or sensitive neuron which are directly interacting with an irritant), and secondary feeling (the external irritant in them interacts with a specialized receptor cell, edges are activated by a sensory neuron).

Local electric potential in primary feeling exteroceptor is called generating since generation of nervous impulses (is connected with it see. Nervous impulse) in the nerve fibril departing from a receptor. In the secondary feeling exteroceptor local potential arises twice — in a receptor cell (receptor potential) and in the termination of a sensory neuron (generator potential since it causes the category of nervous impulses). The initial stages of exteroception in receptors of various types differ from each other. So, in photoreceptors (see) under the influence of light quantums there are chemical transformations of rhodopsin (see) initiating multistage process of transfer of excitement to ion channels of a plasma membrane of a receptor. In chemoceptors (see) under the influence of an adequate irritant there is its linkng with membrane macromolecules of the proteinaceous nature leading to subsequent changes of level of the cyclic nucleotides and calcium ions managing ion channels spatially of the remote electrogene membrane of a receptor.

Many types of exteroceptors are characterized by spontaneous activity, i.e. generation of impulses in lack of an external irritant. The nature of such activity is studied insufficiently, however its function consists in maintenance of the general activity of certain structures of a brain and in distinguishing of the braking irritations exciting I.

Various exteroceptors function is interconnected thanks to efferent influences from those brain structures, in to-rye the relevant information arrives. Most closely the structures of a brain connected with tactile, visual and muscle receptors therefore recognition of a form and size of objects, their arrangement in space, and also the processes of compensation of perception which are observed at people with the lost or underdeveloped receptors are carried out interact.

Frustration E. can be connected with disturbances in the auxiliary device of a receptor (e.g., in photoconductive structures of organs of sight, the sound carrying out structures of acoustic organs) or with pathology of actually receptor structures (e.g., disturbances of biochemical transformations of a rhodopsin), and also owing to development patol. processes in other fiziol. systems of an organism. E.g., at hron. diseases went. - kish. a path, such as gastritis (see), colitis (see), changes of functions of flavoring receptors are observed (see Taste). Disturbance E. it can be observed also at use of nek-ry medicines, e.g. a hearing loss owing to an atrophy of voloskovy cells of a kortiyev of body (see) at the excessive use of streptomycin (see Streptomycin); the decrease in sharpness of taste and its perversion as a result of an atrophy of flavoring receptors caused sn by a zheniye of ion concentration of copper and zinc in a blood plasma at prolonged use of penicillin (see Penicillin).

See also Receptors , Reception .

Bibliography: Esakov A. I. Concept of functional mobility and problem of regulation of touch perception. Messages. USSR Academy of Medical Sciences, No. 1, page 19, 1984; Touch systems, Sense of smell and taste, under the editorship of G. V. Gershuni, etc., L., 1980; Tamar G. Fundamentals of touch physiology, the lane with English, M., 1976; Physiology of touch systems, under the editorship of G. V. Gershuni, p.1 — 2, L., 1971 — 1972.

A. I. Esakov.