DEAFFERENTATION

From Big Medical Encyclopedia

DEAFFERENTATSIYA (Latin the de-prefix extraction, destruction + afferens, afferent [is] bringing) — deprivation of a possibility of carrying out touch excitement from the periphery to the center as a result of disturbance of an anatomic or physiological integrity of sensory nerves. The term «deafferentation» is narrower, than denervation (see), also means the termination of receipt in c. N of page of touch impulsation (acoustical, visual, exteroceptive, proprioceptive etc.); the term «touch deprivation» which is often used also designates the termination of receipt in c. N of page of touch excitement owing to cancellation of irritants of the environment (see. Deprivation ).

The anesthesia in a zone of an innervation is D.'s consequence. Breaks fiziol, properties of nerve centers. E.g., switching off of sensitivity of a hinder leg of a dog leads to increase in excitability of motor-neurons of the corresponding segments of a spinal cord therefore they begin to answer on various excitement, circulating in a nervous system (respiratory, labyrinth, eksteropropriotseptivny, etc.). The Deafferentirovanny paw of a dog begins to move in one rhythm with the respiratory movements of a thorax. At the slightest change of position of the head or trunk, especially at the raised emotional state, and also during the swallowing, bark etc. the deafferentirovanny extremity makes the sharp ex-tensor movements. Therefore, in normal conditions the afferent impulsation going to motor-neurons of a back extremity supports circulation of impulses on a vicious circle within certain segments of a spinal cord (from an extremity to motor-neurons, and from them to an extremity again) and slows down distribution of impacts on them of other functional systems. It is shown also that the deafferentirovanny extremity at rest is in a condition of an inflection or an ekstenziya; at the time of transition of an animal from rest to the movement this extremity at first is in coordinate and proper phase correlations with other extremities. With increase in speed of movements this extremity «drops out» of a coordinate rhythm and is tightened to a trunk. At delay of rate of movements the deafferentirovanny extremity enters the coordinate relations with other extremities again. These observations showed that in the locomotory act the first volley of impulses does not depend on a local afferentation and is integrated at the level of the highest departments of a brain. The subsequent coordination of movements of extremities is supported by means of the local afferent impulses controlling correctness of the motor act. Also reflected movements of a deafferentirovanny extremity in response to the centrifugal impulsation going to other extremities are found. So, e.g., at active raising of a healthy extremity there is a pulling up of a deafferentirovanny extremity advancing the movement of the first by several seconds.

Partial D.'s emergence in the person can serve as a symptom of a row nevrol, diseases. So, at syphilis of a nervous system (see. Back tabes ) the ataxic gate connected with partial D. defeat of back columns is noted spinal cord (see) and reduction of proprioceptive inflow. In this case D.'s compensation happens generally at the expense of a visual afferentation: the patient can go only under control of sight.


Bibliography: Anokhin P. K. Sketches on physiology of functional systems, M., 1975, bibliogr.; Kunstman K. I. and Orbeli L. A. About effects of a deaf-ferentation of a back extremity at dogs, Izv. Leningr, nauch. in-that of P.F. Lesgaft, t. 9, century 2, page 187, 1924, bibliogr.; Shumilina N. I. About the dual nature of motor vozbuzhdeniye in the central nervous system, Fiziol, zhurn. USSR, t. 31, Kya 5-6, page 272, 1945.

A. I. Shumilina.

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