The forebrain is the most rostral branch of the nervous system. It consists of large hemispheres (cortex) and basal ganglia. The latter, located in the cortex, are located between the frontal parts of the brain and the diencephalon. The composition of these nuclear structures includes the caudate nucleus, the shell, which together make up the striatum. It got its name due to the alternation of gray matter, consisting of nerve cells, and white. These elements of the brain, together with a pale ball called pallidum, form the striopallid system. This system in mammals, including humans, is the main nuclear apparatus and is involved in the processes of motor behavior and other important functions.
The structure of the basal ganglia includes subcortical nuclei, which have a very diverse cellular composition. Large and small neurons are located in a pale sphere. The striatum has a similar cellular organization. Impulses from the cortex of the hemispheres, thalamus, stem nuclei go to the neurons of the striopallid system.
What functions do the subcortical nuclei perform ?
The nuclei of the striopallid system participate in the coordination of movements and motor activity. Irritation of the caudate nucleus causes head rotations of a stereotypical nature and trembling movements of the arms or forelimbs in animals. In the process of studying the striatum, it was found that it matters in the processes of memorizing movements. The irritating effect on this structure disrupts the processes of memory and learning. The striopallidar system has an inhibitory effect on motor activity and its emotional components, for example, on aggressive reactions.
Cerebral cortex
The forebrain includes a formation called the cortex. She is considered the youngest brain formation. Morphologically, the cortex consists of gray matter, which covers the entire brain and has a large area due to numerous folds and convolutions. Gray matter consists of a huge number of nerve cells. Due to this, the number of synoptic connections is very large, this ensures the storage and processing of the information received. Based on the appearance and evolution, the ancient, old and new bark are distinguished. During the evolution of mammals, the new cortex developed especially rapidly. The ancient bark in its composition has olfactory bulbs and tracts, olfactory tubercles. The structure of the old includes the cingulate gyrus, tonsil and gyrus of the hypocampus. The remaining areas belong to the new crust.
Nerve cells of the cortex of the hemispheres are arranged in layers and orderly, forming six layers in their composition:
1st - called molecular, formed by the plexus of nerve fibers and contains a minimum number of nerve cells.
2nd - called external granular. It consists of small neurons of various shapes, similar to grains.
3rd - consists of pyramidal neurons.
4th — the inner granular, like the outer layer, consists of small neurons.
5th - contains Betz cells (giant pyramidal cells). The processes of these cells (axons) form a pyramidal tract, which reaches the caudal areas and passes into the anterior roots of the spinal cord.
6th - multiform, consists of triangular and spindle-shaped neurons.
Although the neural organization of the cortex has much in common, a more detailed study of it showed the differences that appear during the course of the fibers, the size and number of cells, and the branching of their detritus. Studying the human brain, a map of the cortex was compiled, which includes 11 regions and 52 fields.
What is the forebrain responsible for ?
Very often, the ancient and old bark are combined. They form the olfactory brain. The forebrain is also responsible for alertness and attention, is involved in autonomic reactions. The system takes part in instinctive behavior and the formation of emotions. In experiments on animals, with an irritating effect on the old bark, effects associated with the digestive system appear: chewing, swallowing, peristalsis. Also, the irritating effect on the tonsils causes a change in the function of internal organs (kidneys, uterus, bladder). Some areas of the cortex are involved in the processes of memorization.
Together, the hypothalamus, limbic region and forebrain (ancient and old cortex) form a limbic system that preserves homeostasis and ensures the preservation of the species.