What the cerebral cortex is responsible for: precentral gyrus

The function of the human brain is to control processes throughout the body, as this is the main part of the central nervous system. It is divided into zones, each of which is responsible for a specific process. For example, for coordination of movements, muscle tone, reactions to external influences. The patterns of the brain are studied for a better understanding of the human psyche. This article will consider one of its most important parts - the bark.

The functions of the cerebral cortex

The functions of the cerebral cortex include:

1. The definition of intelligence.
2. Identification.
3. Motor function.
4. Planning and organization.
5. Sensation of touch.
6. Processing sensory information.
7. Language processing.

A number of disorders arise as a result of damage or death of cells of the cerebral cortex. Surviving symptoms depend on the area of ​​the cortex that is damaged. Possible consequences:

• inability to perform certain motor tasks (difficulty walking or interacting with objects);
• agraphia (inability to write);
• ataxia (incoordination);
• depressive disorders, difficulty in making decisions, problems with memory and attention.

Primary motor cortex (precentral gyrus or Broadman’s fourth field)

It is a region of the brain that is located in the back of the frontal lobe. The precentral gyrus is responsible for the conscious movements of the body. It works in combination with other motor areas, including the premotor cortex, parietal lobe and several subcortical areas of the brain, so that a person can plan and perform movements. The considered gyrus contains large neurons, known as Betz cells, which along with other cortical neurons send impulses along long axons down the spinal cord, that is, they transmit signals to the muscle system.

Each hemisphere of the brain is responsible for the opposite side of the body. The amount of primary motor cortex intended for a part of the body is not proportional to the size of its surface, but corresponds to the density of skin motor receptors. Thus, human hands and face need more control of Broadman’s fourth field than legs.

Structure

The precentral gyrus is located on the front wall of the central sulcus. It borders on the resulting lateral premotor cortex, and posterior to the primary somatosensory cortex.

The location of the primary motor cortex is easily determined in histological studies due to the presence of Betz distinctive cells. One of its layers contains giant (70-100 micrometers) pyramidal neurons. They send impulses along long axons to the motor nuclei of the cranial nerves and to the lower motor neurons in the ventral horn of the spinal cord. Axons form part of the cortical-spinal tract, where Betz cells make up about 10% of the total. But they provide clear boundaries of the precentral gyrus.

Blood supply and functions

The branches of the middle cerebral artery provide most of the arterial blood supply to Broadman’s fourth field.

Various parts of the body are displayed on the precentral gyrus in the form of the so-called homunculus (small person). The foot zone corresponds to the midline and forms a longitudinal gap in the internal parts of the motor zone. The lateral convex side is located from top to bottom in places that are responsible for the movements of the buttocks, trunk, shoulders, elbows, wrists, fingers, eyelids, lips and jaws.

It is worth recalling that the parts of the motor cortex are not proportional to the size of their body parts, and the lips, facial features and hands (the most mobile) are represented by especially wide parts. After amputation or paralysis, the motor zones may shift to accept new parts of the body.

Betz cells

The giant pyramidal cells of the precentral gyrus are sometimes mistaken for a single or main exit of the cortex into the spinal cord. Nevertheless, Betz cells make up only about 2-3% of the neurons that bind the cortex and spinal cord, and only about 10% of the neurons that are formed in the primary motor cortex. A number of cortical regions, including premotor, additional motor and even primary somatosensory, have access to the spinal cord.

Even when Betz cells are damaged, the cortex can still bind to subcortical motor structures and control body movements. If the precentral gyrus is damaged, temporary paralysis occurs, and other areas of the cerebral cortex, obviously, can take on part of the lost function.

Lesions of the fourth Broadman’s field lead to paralysis of the contralateral side of the body (facial paralysis, arm / leg monoparesis, hemiparesis).