By structure, the human nervous system is divided into central and peripheral.
The central nervous system (CNS) is formed by the brain and spinal cord.
The peripheral nervous system includes 12 pairs of cranial nerves, 31 pairs of spinal nerves, plexuses and nodes throughout the body.
According to functional characteristics, the nervous system is divided into somatic and autonomic. Each of these sections has a central part, located in the brain and spinal cord, and a peripheral part, represented by nerves, nerve nodes and endings.
- * The somatic nervous system controls skeletal muscles, establishes a relationship with the environment. With the participation of this department, the human brain receives information about the external environment and its effect on the body (for example, temperature changes, pain, touch, etc.). With its help, a person voluntarily (i.e., voluntarily) performs different movements.
- The autonomic (autonomic) nervous system (ANS) regulates the work of internal organs, controls the activity of smooth and cardiac muscles, the work of the glands, metabolic reactions, maintaining the constancy of the internal environment in the human body. The person himself cannot control the work of this system (for example, it is impossible, for example, to stop the heart at will, to speed up the digestion process, to delay perspiration), that is, it works involuntarily.
In the autonomic (autonomic) nervous system, two divisions are distinguished: parasympathetic and sympathetic. As a rule, the nerves of these two sections exert opposite influences on the internal organs.
Parasympathetic nerve impulses weaken cardiac activity, dilate the blood vessels of the skin, lower blood pressure, and lower blood glucose levels.
The sympathetic nervous system speeds up and strengthens the work of the heart, increases blood pressure, narrows the vessels of the skin, and inhibits the work of the digestive system.
Example: some organs are supplied with only one type of autonomic nerve fibers (for example, the sweat glands and the adrenal medulla are innervated only by sympathetic nerves).