MEDIATORS – substances formed in the nerve endings and transmitting excitation from one nerve cell to another or from the nerve ending to the working organ (muscle fiber,

MEDIATORS

– substances formed in nerve endings and transmitting excitation from one nerve cell to another or from a nerve ending to a working organ (muscle fiber, glandular cell, etc.). When any organ or tissue is irritated in the nerve endings that permeate the skin, mucous membranes, muscles, joints and all internal organs, a nerve impulse occurs – a signal that is transmitted through sensitive fibers to the central nervous system (spinal cord and brain) . From the central nervous system, the impulse travels along the motor nerves directly to the muscles and causes their response.

In order for the impulse to cause excitation of the nerve cells of the brain, and then switch from the motor nerve ending to the muscle, a chemical is needed. intermediary mediator. Experimental study of mediators began with the discovery of the Austrian. physiologist and pharmacist O. Levy in 1921 of the fact that a solution washing the active drug of an isolated frog heart can act on another similar drug like a direct irritation of the heart. Electron microscopic studies have shown that neurotransmitters are contained in numerous vesicles that form at the point of contact between the nerve endings and the body of the nerve cell, in the so-called. synapses. In the process of nervous excitation, part of the synaptic vesicles bursts and their contents interact with the membrane of a nerve or muscle cell, exciting this cell. It has been established that M.'s release occurs not only during excitation, but also during inhibition of all departments of the central and peripheral nervous system. At the vagus nerve endings it is acetylcholine, and at the sympathetic nervous system endings it is norepinephrine. Along with acetylcholine and norepinephrine, other M. were also found, such as histamine and bradykinin, which cause capillary dilation, serotonin, which constricts blood vessels and depresses the central nervous system, and others.

Research M. gave important results for the clinic. It turned out that in a number of diseases of the nervous system and with certain poisonings, the formation, action or decay of M. is disturbed, on the basis of which new methods of treating these diseases are recommended and put into practice. No less important was the discovery of the influence of a number of substances that prevent the transfer of excitation with the help of M.

Since ancient times, substances such as curare have been known, which were used by hunters, lubricating the tips of their hunting arrows to immobilize animals.However, the mechanism of action of these substances was opened relatively recently. It turned out that they prevent the transfer of excitation by blocking the action of M., after which even artificial irritation is unable to cause the excitation of muscle fiber. Rough preparations were widely used in surgical practice when there is a need to produce operations under breathing off.