From Big Medical Encyclopedia

MOTOR REACTIONS (synonym: motive reflexes, reflexus motorii) — the movements caused by irritation of sensitive nerve terminations or excitement of c. N of page, extending on centrifuge fibers to effectors (muscles). The inborn and acquired by D. rubles (unconditional and conditional D. distinguish river, according to I. P. Pavlov). Inborn D. of river are implemented through so-called reflex arcs. The rubles acquired by D. arise on the basis of inborn in the course of individual training and therefore are more plastic. Both the inborn, and acquired by D. rubles it is possible to classify by touch character (a touch modality) of the incentive operating on afferent nerve terminations (light, sound, tactile etc.); according to characteristics of the Wednesday creating stimulation of receptors (exteroceptive, proprioceptive, interoceptive); on the level of the nervous structures participating in the organization D. of river (segmented, trunk, cortical); on the volume of a physical activity (simple — like a knee jerk, difficult — like locomotions, the providing movements in time and space) and its biological importance (food, defensive, approximate and research, sexual and other D. R.) - Of river make a basis of life activity of an organism, providing a possibility of its self-preservation, preservation of a look, self-expression and communication. Labor processes, sports activities, the letter, the speech and other purely human types of a physical activity also represent D. of river. At the same time similar motive activity of the person — his motility — can be described only conditionally, i.e. nervous mechanisms of motive activity of the person are very difficult and do not keep within rather simple ideas of D. of river.

History of studying of D. of river is connected with names of the Russian scientists. So, creation of theoretical bases of D. of river belongs to I. M. Sechenov, their further development is connected with V. M. Bekhterev, I. P. Pavlov and N. A. Bernstein's works who managed to generalize results of studying of motive frustration of the person in clinic and results of a research of labor, household and sports movements of the person.

The structurally functional basis of motor reactions is made by the receptor field, neurons of c. N of page and muscle. The receptor field represents the first structure, without cut D. cannot be carried out by river. The most bystry are D. of rubles whose receptor fields are located on skin, in muscles, sinews and joint bags. D.'s regulation by the river is carried out by means of neurons of c. N of page at all its levels. The number, level, localization and the nature of interaction of neurons define character and D.'s complexity of river. Cross-striped muscles are actually D. performers of river. D. are implemented by river all listed above structures on condition of the consecutive communication between them which is carried out by nerve fibrils.

The irritation of the receptor field generates the flow of nervous impulses going to sensory neurons of c. N of page (see. Motor analyzer ). Excitement extends in structures of c. the N of page also reaches its motor departments containing motor-neurons (motor fields of a cerebral cortex, subcrustal kernels, motor-neurons of a spinal cord). Motor department of a simple knee tendon jerk are motor-neurons of a spinal cord. Motor ways of more difficult D. of river begin in bark of hemicerebrums.

The flow of nervous impulses from motor-neurons to a muscle causes reduction of its muscle fibers. Reduction of a muscle in most cases involves change of a corner between bones in a joint, i.e. the movement. Depending on a problem of the movement various muscles work either consensually, or retsiprokno. Associations of big muscular groups in spatio-temporal complexes (so-called synergy) simplify process of management of river of difficult D. (see. Movements, biomechanical bases ). Process control of the movement is directly connected with a number of consecutive transformations in receptors, the central neurons and muscle fibers: in receptors external energy (e.g., mechanical) will be transformed to the generator potential of a receptor in the beginning, and then — to the action potential which is transferred on afferent nerve fibrils to the central neurons; in the central neurons the coming touch categories will be transformed to action potentials of motor-neurons, and muscle fibers, receiving action potentials of motor-neurons, carry out transformation of nervous impulses to muscular contraction. The standard point of view concerning the nature of bonds between separate neurons is idea of discontinuity in implementation of transfer of excitement through a synaptic gap by means of special chemical substances — mediators (see).

Methods of a research. The most informative methods of a research D. of river allow to study the certain nervous and muscular structures participating in D. of river separately and to receive at the same time quantitative estimates. As an example of obtaining quantitative characteristics of D. of river realized by various central nervous structures reduction of a tricipital muscle of a shin and the movement of a separation of a heel in response to irritation electric current of a surface of skin can serve in a popliteal space over a tibial nerve. Elektromiografichesky studying of this reflex shows that stage of latency of response makes 25 — 35 microseconds. Short stage of latency of the answer testifies to the spinal level of implementation of D. of river. If to take into account that at the person the speed of carrying out on the fast-carrying most out afferent fibers does not exceed 120 m/s, and on motor fibers — 90 m/s, then time of passing of an impulse from an afferent fiber of a tibial nerve to a spinal cord will average 10 microseconds, time of passing on axons of motor-neurons of a spinal cord to a neuromuscular synapse will make apprx. 12 microseconds. Thus, only on passing of an impulse on the nervous conductors connecting area of stimulation to the corresponding segment of a spinal cord not less than 22 microseconds are required. It is known also that time of passing of nervous impulse through one synapse makes apprx. 1 microsecond. Therefore, the structures responsible for implementation of such reflex do not go beyond segments of a spinal cord. D.'s characteristics of river are depending on the size of an incentive and a functional condition of c. N of page. Apply a so-called method of measurement of time of D. of river to a research of the rubles acquired by D. in whose organization structures of bark of hemicerebrums take part. At the examinee after the preliminary instruction study reaction to an external signal (e.g., flash of light); D. is in reply carried out by river. However at similarity of external manifestations between the inborn and acquired D. the ruble is essential distinctions which are defined by levels of nervous control. So, stage of latency of the river acquired by D. on average makes 160 — 200 microseconds and does not happen (at the healthy person) less than 100 microseconds (see. Miografiya , Electromyography ).

See also Motoriums, ways .

Bibliography: Bernstein N. A. About creation of movements, M., 1947; Bekhterev V. M. Conduction paths back and a brain, M. — L., 1926; Granite P. Bases of regulation of movements, the lane with English, M., 1973; Kostya to P. G. Struktura and function of the descending systems of a spinal cord, L., 1973; Milner P. Physiological psychology, the lane with English, page 470, M., 1973; P and in l about in I. P. Complete works, t. 3, book 1 — 2, M. — L., 1951; Sechenov I. M. Chosen works, page 167, M., 1935; Physiology of movements, under the editorship of V. S. Guofinkel, L., 1976; Experimental psychology, under the editorship of P. Fress and Ge. Piaget, lane with fr., century 1-2, page 314, M., 1966; Homburger A. Motorik, Handb. d. Geisteskrankheiten, hrsg. at. O. Bumke, Bd 9, S. 211, B., 1932; Jaspers K. Allgemeine Psychopatho-logie, B., 1959.

H. A. Rokotova.