Motor reactions (associated with muscular contraction) are one of the most common types of reflex reactions of the body (see Reflexes ), which provide orientation and movement of the body in space.
By the nature of muscle contractions, all motor responses can be divided into two categories: reactions that ensure the tone of muscle fibers, - long-term tonic contractions; reactions that provide local movements are phasic.
By themselves, phasic motor reactions may vary in direction, nature of movement. In this regard, there are movements that provide flexion, extension, adduction, abduction, rotation of the limb in the joint. Muscles that provide these types of motor reactions, received the appropriate names: flexors, extensors, etc.
Very often these muscles act as antagonists. So, flexion of the leg at the knee joint , provided by the contraction of the flexors, is accompanied by relaxation of the extensors. But quite often these muscles act as synergists, that is, they work simultaneously. So, when fixing the leg in the knee joint, simultaneous contraction of different muscle groups is required.
Tonic and phasic muscle reactions are carried out simultaneously, providing a holistic motor act.Go
No local muscular movement (for example, raising the arm) can be carried out without first moving the body's center of gravity and fixing the posture. Otherwise, the person who raised his hand would immediately fall as a result of the imbalance of the body .
Any integral motor act (walking, running, jumping, etc.) can be studied from the point of view of the participation of various muscle groups in the implementation of this act, the amplitude of movement, the degree of flexion or extension of a limb in a particular joint, etc. Section Physiology, dealing with the study of the mechanics of the movement of animals and humans, is called biomechanics.
Any, even the simplest motor act is the result of a very complex and finely coordinated work of many muscle groups, which in turn reflects the very complex processes occurring in the central nervous system. An important role is played by the motor, or kinesthetic, analyzer. The latter, like any other, consists of three main links: peripheral, represented by proprioceptors (muscle spindles, Golgi receptors , Pacini body) located in the motor apparatus itself (in muscles, tendons, articular bags, etc.); a conductor region consisting of nerve fibers conducting proprioceptive excitations to the cortex of the cerebral hemispheres; cortical level, represented by the area of the cortex, which receives the excitation from the muscular-articular receptors.
With the help of the motor analyzer, it is possible to assess the strength of muscle contraction, the amplitude and direction of movement, the position of the body in space, etc.
The development of movements in children - see Infant.
Pathology of movements . Disorders of motor reactions occur with the defeat of the pyramidal path (central motor neuron), subcortical nodes, brain stem, cerebellum , spinal cord and peripheral neuron coming from the cells of the anterior horns of the spinal cord (as part of the anterior roots). Complete loss of motion is called paralysis, partial - paresis.
With central paralysis, there is a lack of active movements, a decrease in muscle strength, an increase in muscle tone, an increase in tendon reflexes, the appearance of pathological reflexes and pathological friendly movements. In peripheral paralysis, the loss of voluntary, friendly and reflex movements, atony, areflexia, muscle atrophy, and in some cases, twitching.
With the defeat of the extrapyramidal system , oligokinesia or bradykinesia appears (see) and hyperkinesias (see). With the defeat of the cerebellum (see) there is an excessive amount of involuntary movements and a violation of their coordination. With the defeat of the parietal lobe and the posterior columns of the spinal cord, sensitivity disorders are noted.