Cerebellum

Physiology

Modern knowledge on physiology of the cerebellum is based on data obtained by the methods of partial or total destruction, irritation and registration of action potentials of this body. The most accurate knowledge about the functions of the cerebellum are associated with the name of Lucani [Luciani (L. Luciani, 1893)], in accordance with the ideas of which M - the body that regulates the neuromuscular activity by scenicheskoe, tonic and static action. This means that M increases the force of muscle contraction during movement, and their tone in periods of functional peace and promotes the development of sustainable solid tehnicheskogo muscle contraction. Therefore, the loss of function of the cerebellum leads to the appearance of the classical triad of Lucani: asthenia, atony and Ustashi. Fatigue is expressed in weakening the force of muscle contraction, atony - low muscle tone, astasia - in the loss of the muscle's ability to continuous tehnicheskomu reduction. All this syndrome leads to musculoskeletal disorders known as the cerebellar ataxia (see). In the drop function M gecirebilirsiniz animals become motor disabilities: they lose the ability to walk in a straight line, to keep the torso in a stable position (wobbly, "drunk" gait); when walking disproportionate to move the limbs (legs put it far from the middle line, close to it, often capturing left leg to the right, and Vice versa); the movements are jerky, on the background of the growing, weakened rocking the whole body (see Balance of the body).
Exploring the impacts of removing cerebellum allowed Lucani to distinguish three periods in the evolution of mobility impairments in animals. 1. The period of dynamic phenomena (1st week after the operation) is characterized by the strengthening of the animal extensor tone that leads to periodic extensor spasm front legs, severe crowding the head, arching body (opistotonus). In the same Period of forced movement: the rotation about the longitudinal cap and the other 2. The period of loss of, or failure (for 2-4 weeks I) is characterized by the appearance of the symptom complex of motor disorders, expressed asthenia, atony and astasia. 3. The period of compensation (end of the 1st month) is expressed in the gradual reduction of cerebellar disorders; compensation, however, is partial: gecirebilirsiniz animals motor disorders are detected even after 7 to 8 years.
Local destruction in the experiment, the most ancient part of the cerebellum (nodulus) leads to the appearance of cats, dogs, monkeys, including the chimpanzee syndrome imbalances without any other symptoms experienced at total destruction M [Dau (K. S. Dow)]. The destruction floccule-nodular Department M. leads to the extinction of the conditioned reflexes to swing the camera where you have placed the dog. However, as has operated animals compensatory devices (see), restore the reaction not only on the strong and weak swing the camera (S. N. Khechinashvili).
Despite the elegance of the teachings of Lucani, experimental validity of many of its provisions, further research has made significant additions and changes to this doctrine.
A new major stage in the development of modern ideas about the functions of the cerebellum was the investigation of L. A. Orbeli and his school. He managed not only to confirm the whole picture motor disorders in gecirebilirsiniz animals, but also to establish a number of new and important facts. In the most significant issue of muscle tone was able to show that it's not the loss of tone in bestuzhevyh animals, and in his frustration, in the wrong distribution of tone between individual muscle groups.
Numerous experiments L. A. Orbeli with TCS. other authors [Moruzzi (G. Moruzzi) and others] have shown the importance of the cerebellum in trophic functions of the organism. Thus, it is established that the extirpation of the cerebellum leads to various disorders of the gastrointestinal tract (reduced tone muscles of digestive apparatus, lowering evacuation ability of the stomach and small intestines, the change in the secretion and absorption of activity). Destruction M increases the range of fluctuations of blood sugar, to change the content To and Sa. Chemical or electric irritation M. causes a change in the function of the cardiovascular and respiratory systems leads to oppression or facilitate reflexes from pressoreceptor. Extirpation of the cerebellum immature female animals in many cases leads to a delay of puberty, the underdevelopment of reproductive organs (the dog) and lactation failure (cat).
Based on all data received, L. A. Orbeli formulated the concept of M. as adaptation of higher-trophic centre, regulating functional readiness and functional status of all parts of the nervous system, all organs and body systems. The role of the Supreme regulator of neurological function and trophic regulation of the cerebellum implements together with the bark of the big hemispheres through intercentral, vegetative and humoral links based on a constant stream of afferent alarm.
Neurological studies in recent years have shown that M is not only the device, which has efferent connection with various departments of the Central nervous system, but also the body to which the projected variety of afferent systems.
Electrophysiological found that pulses from musculoskeletal not only reach the cerebellum, but have here some topographically defined localization. Registering biopotentials M at the irritation of the limbs of animals (cats and monkeys), Adrian (Adrian E. D.) found that opens in strict sequence localization caused the afferent discharge. In another series of experiments, irritating (current or strychnine) different departments of motor areas of the cerebral cortex, he found in the cerebellum topographically defined projection corresponding cortical areas of the face, upper and lower extremities. These projection area coincided with the areas obtained by irritation of the limbs. MC-Inter (A. K. McJntyre) showed that the afferent impulses from muscle receptors (intrafusal muscle fibers) reach M. These data suggest that M - a body, which presents afferent paths from muscular-articular apparatus. Snyder, Stowell (C. S. Snider, Stowell) showed that the auditory, visual and tactile afferention also presented in the cerebellum, and L. A. Firsov, K. M Kullanda and others have shown the presence in M. projections of the AIDS interoceptive alarm.
Thus, M is represented in the form of anatomical education, where the projected afferents external and internal alarm. Due to the presence of cerebellar system afferent alarm cortex (see) receives double projection sensor systems: one through the brain stem, the second one via PM


Electrophysiological studies have shown that evoked potentials, registered in the bark of the big hemispheres of a brain after bilateral destruction medial loops change significantly following the complete removal of the cerebellum.
This, however, does not mean that M is a guide to the information from the periphery to the big hemispheres. This Department of the Central nervous system (like all others) along with afferent system is endowed also efferent management system. The presence of afferent alarm provides specific cerebellar level of analytical and synthetic activity, which finds its output via efferent "gate" this naselennogo management personnel. Being the closest accomplice of the cerebral cortex in adaptation and trophic regulation neurological functions, modulation and stabilizing functional readiness of all reflex systems and devices, Meters, has a bilateral, circular connection with all structural units of the Central nervous system. Through these connections, and are facilitating and inhibiting the effects of the cerebellum to spinal centers, centers of the trunk and the cerebral cortex. This means that M is an essential link in the structure of external and internal analyzers (see) and primarily in the structure of the motor analyzer [L. S. Ghambaryan; Kreindler (A. Kreindler)].
As a structural element motor analyzer M. receives information from muscular-articular apparatus and via efferent system regulates relations coordinated activity of alpha - and gamma-efferent systems, and hence the receptor function of muscle spindles. Afferent discharge from muscle spindles enhances the irritation hemispheric departments front of the cerebellum and severely oppressed, and sometimes blocked when the irritation of his worm zone (culmen).
Regulation of afferent functions spindles M performs through gamma motoneurone spinal cord (see). When you activate gamma afferent happens spasm intrafusal fibers and as a result increases the afferent impulses from the receptor apparatus of spindles. The high activity of muscle receptors on the mechanism ring feedback supports the activity of alpha-motoneurons spinal cord, causing tonic extrafusal muscle contraction. When oppression gamma afferent observed the opposite value. Thus, the increased activity of gamma-fibers is an important factor in the mechanisms of support and regulation of muscle tone [Granite (Century Granit)]. At loss of function M animals are deprived of the possibility to use their "measuring instruments" in the muscle spindles (see Receptors), and this leads to dysmetria, the violation of the regulation of muscle tone and other motor disorders.
According to L. A. Orbeli, Beznosikov animals, being the motor disabled, find extremely sophisticated higher nervous activity and seem to be even compared with normal dogs especially "intelligent". This is confirmed by experiments on studying the conditioned reflex activity in bestuzhevyh dogs. However, some experiments conducted in the conditions of free movement, show that, with the removal of the cerebellum is broken correct spatial conditioned reflex orientation animals sounds and a place of refreshment. Cm. also the brain.