From Big Medical Encyclopedia

DOMINANT (Latin dominans, dominant [is] dominating) — the center of excitement in the central nervous system directing complete activity of an organism at present and under existing conditions.

— a special condition of nerve centers (see. Centers of a nervous system ), characterized hypererethism, firmness and inertia of the arising process of excitement, i.e. ability to hold and continue time the begun excitement. This property D. can lead to emergence in c. N of page of the «congestive» center of the excitement capable to cause functional disturbance of mental activity.

Emergence of the «congestive» center of excitement as a result of the repeating negative emotional impacts can be an origin of a number of diseases, such as an idiopathic hypertensia, stenocardia, a peptic ulcer, etc.

The dominant center (center) represents set of structures of c. N of page with selective a hyperexcitability, capable to sum up excitement and creating a certain reflex activity of an organism during the drawing any irritation, irrespective of its origin and quality. Methods of artificial creation of the dominant center, napr, by means of polarization by the anode of a small direct current or application pharmakol, substances are developed (strychnine, etc.) on various areas of bark and subcrustal structures.

The doctrine about D. is developed by A. A. Ukhtomsky. The following fact was the basis for the doctrine: at the dog preparing for defecation, the irritation of the site of the motor area of bark of big cerebral hemispheres caused the full act of defecation instead of motor reactions of extremities. The act of defecation prepares a continuous stream of afferent impulses from receptors of a rectum for nerve centers that leads to increase in their excitability. In these conditions excitement of the centers of defecation accrues already under the influence of the impulses coming to c. N of page irrespective of the place and quality of irritation. Increase in excitability in nerve centers and D.'s formation can be caused not only an afferent impulsation, but also hormonal influences. So, at males of frogs during the spring period in connection with increase in level of sex hormones the strong «obnimatelny reflex» is observed; due to reduction of sgibatel of front extremities the male strong clasps a female, holding it in such situation during the entire period of a throwing of caviar. Drawing irritation on a body surface of a male instead of causing the corresponding defensive reflex, strengthens tension of muscles of sgibatel of front extremities.

D.'s opening showed that the net result of reflex reaction of an organism is not defined entirely by carrying out impulses from receptors to effector to bodies for the isolated ways according to classical ideas of reflex arcs, and in many respects depends on a functional condition of nerve centers.

In the conditions of D. the arising center of excitement brakes all other reflexes on the next irritants, subordinates to itself activity of other centers and represents the system of bonds dominating in an organism combining nervous elements of various levels of c. N page and peripheral bodies.

Under natural conditions not the center of excitement, but this or that functional system dominates (see. Functional systems ), providing achievement of adaptive result, useful to an organism.

In D.'s organism evolves from the motivational excitement dominating at present (see. Motivations ). In this regard allocate food, sexual, defensive and other views of. During pregnancy change of all functions in an organism of the woman is directed to successful incubation of a fruit.

This orientation is connected with formation in D.'s organism of the pregnancy submitting we blow to the patterns characteristic for D. Takaya D.

Neyrofiziol, the mechanism creating D. — the ascending activating influences of the centers of a hypothalamus and a reticular formation of a brain selectively strengthening the level of excitement in certain cells of bark of big cerebral hemispheres increasing their excitability and increasing the volume of convergence of arousing various quality forms in connection with emergence of interoceptive impulses from a uterus, change of activity of hemadens, emergence of a placenta, action of products of exchange of a fruit etc. In turn the descending influences of certain areas of a cerebral cortex selectively facilitate carrying out excitement on relay kernels of a thalamus and a reticular formation. In these conditions practically any irritations cause summation of processes of excitement in the corresponding nerve centers and lead to the organization of the complete activity providing to an organism achievement of useful result. The mechanism D. takes part in formation of an initial stage of the central architecture of any functional system — a stage afferent synthesis (see).

The doctrine about D. opens universal pattern in activity of a complete organism. Mental activity of the person submits to the principle D.; once having arisen, D. is capable to create active purposeful behavior and to be a driving factor of intellectual development, moral and ethical motives.

Bibliography: Anokhin P. K. Internal inhibition as problem of physiology, M., 1958, bibliogr.; it, Biology and neurophysiology of a conditioned reflex, M., 1968, bibliogr.; Arshavsky I. A. Dominant of pregnancy and problem of physiologically full ontogenesis, Trudy Nauch. - issled, in-that biol, and biol, f-that Harkovsk. un-that, t. 24, page 161, 1956; Konradi G. P. Transition of a dominant to braking, Collection of works fiziol. laboratories Leningr, un-that, page 118, M. — L., 1930; V. S. Dominant's Russinians, M., 1969, bibliogr.; K. V pike perches. Biological motivations, M., 1971; it, the Dominating motivation as a basis of purposeful activity, in book: The touch organization of movements, under the editorship of A.S. Batuyev, page 204, L., 1975, bibliogr.; Ukhtomsky A. A. Collected works, t. 1, page 31, L., 1950.

S. A. Osipovsky.