Under the cerebral cortex there is a group of anatomically isolated paired structures - the basal nuclei (ganglia). Together with other nuclei of the middle and diencephalon, they affect motor activity, which has a different function than the cerebellum. The difference is that the basal nuclei of the cerebral hemispheres do not contain a direct entrance from the cerebral cortex. Ganglia affect the motor parts of the cerebral cortex, participate in cognitive and emotional functions.
Basal nuclei significantly affect the cerebral cortex. Their dysfunction leads to impaired movement. The disorder is explained by a significant role in the work of the lateral system of motor abilities. If the basal nuclei of the cerebral hemispheres are affected, then the symptoms are as follows: the tone and muscular position are disturbed. The basal nuclei soften the movements that occur during the "start" of their cerebral cortex, and also suppress excessive movements. Organized projections come in parallel. They begin from the frontal areas, somatic sensory, motor areas, as well as from the crown of the head, temples, nape.
The basal nuclei of the brain consist of the striatum, which includes the amygdala, fencing, lenticular and caudate nuclei.
- The amygdala is located in the temporal region. In this zone, the crust is somewhat thickened;
- The fence is outside the nucleus (lenticular). It has the form of a plate with a thickness of two millimeters. Its front part is thickened. A protrusion of gray matter is characteristic on the lateral margin. The medial edge of the fence is flat;
- The lenticular nucleus is located outward from the caudate. Small accumulations of white matter divide the core into three parts.
- The caudate nucleus is involved in the formation of the upper wall of the lateral ventricular horn.
The basal nuclei do not have a direct path to the spinal cord. From the striatum to the reticular region of the substantia nigra and the medial pale sphere, inhibitory (GABAergic) fibers are located. Their functional orientation is based on the increased influence of the excitation of the thalamic nuclei on the parts of the motor cortex responsible for the necessary movement.
The organization of an indirect path is quite complicated. The process consists in suppressing the excitation of the thalamus to other areas of the motor cortex. The first section of the path contains GABAergic inhibitory projections of the striatum onto a lateral pale ball. The latter sends brake fibers to the thalamus nucleus. The outputs of the core are filled with exciting fibers. Some of them are sent to a pale lateral ball. The remaining fibers move to the reticular zone of the substantia nigra and the pale medial ball. From this it follows: if the activating effect of the direct path from the striatum increases the excitatory activity of the motor cortex, then the activity of the indirect path weakens.
Dysfunction of the subcortical nuclei leads to a disorder of the human motor abilities. They become either excessive or absent altogether. Parkinson's disease should be mentioned as an example. People affected by this disease acquire a face mask. Walking is done in small steps. It is difficult for a person to start and end movements. Trembling (tremor) of the extremities is observed , muscle tone increases. Parkinson's disease occurs due to impaired conduction of nerve impulses from the substance to the striatum. The defeat of the striatum leads to excessive movements: twitching of the cervical and facial muscles, trunk, arms, legs. Increased activity in the form of aimless movement of the body can also be observed.
In conclusion, it should be noted that a personβs vital ability depends on the normal functioning of the brain. The slightest deviation in the brain leads to various diseases, disabilities, and sometimes to complete paralysis. Therefore, avoid injuries, do not expose yourself to unnecessary dangers, undue risk.