The central nervous system (CNS) is the main part of the nervous system of animals and humans, consisting of an accumulation of nerve cells (neurons) and their processes; it is represented in invertebrates by a system of closely interconnected nerve nodes (ganglia), in vertebrates and humans — by the spinal cord and brain.
The main and specific function of the central nervous system is the implementation of simple and complex highly differentiated reflective reactions, called reflexes. In higher animals and humans, the lower and middle sections of the central nervous system — the spinal cord, medulla oblongata, midbrain, diencephalon and cerebellum — regulate the activity of individual organs and systems of a highly developed organism, carry out communication and interaction between them, ensure the unity of the organism and the integrity of its activity. The highest department of the central nervous system — the cerebral cortex and the nearest subcortical formations — mainly regulates the connection and relationship of the body as a whole with the environment.
The main features of the structure and function
The central nervous system is connected with all organs and tissues through the peripheral nervous system, which in vertebrates includes cranial nerves extending from the brain, and spinal nerves — from the spinal cord, intervertebral nerve nodes, as well as the peripheral part of the autonomic nervous system — nerve nodes, with him (preganglionic) and departing from them (postganglionic) nerve fibers. Sensitive, or afferent, nerve adductor fibers carry excitation to the central nervous system from peripheral receptors; along the efferent efferent (motor and autonomic) nerve fibers, excitation from the central nervous system is directed to the cells of the executive working apparatus (muscles, glands, blood vessels, etc.). In all parts of the CNS there are afferent neurons that perceive stimuli coming from the periphery, and efferent neurons that send nerve impulses to the periphery to various executive organs. Afferent and efferent cells, with their processes, can contact each other and form a two-neuron reflex arc that performs elementary reflexes (for example, tendon reflexes of the spinal cord). But, as a rule, interneurons, or interneurons, are located in the reflex arc between the afferent and efferent neurons. Communication between different parts of the CNS is also carried out with the help of many processes of afferent, efferent and intercalary neurons of these parts, which form intracentral short and long pathways. The CNS also includes neuroglial cells, which perform a supporting function in it, and also participate in the metabolism of nerve cells.