Go Thermoregulation human heat exchange
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Thermoregulation

Thermoregulation (heat exchange) is a combination of physiological processes in the body of warm-blooded animals and humans, ensuring the maintenance of a constant body temperature at a certain level with very small fluctuations.

The temperature of the internal environment of the body is maintained at a relatively constant level according to the principle of self-regulation, according to which the deviation of temperature from the level that ensures normal vital activity is a stimulus that returns it to this level. The set of structures that provide self-regulation of the temperature of the body, is the so-called functional system of thermoregulation (P. K. Anokhin).

The constancy of body temperature is provided by two oppositely directed processes - heat production and heat transfer.

Heat production, i.e. the generation of heat in the body, depends on the intensity of metabolic processes, so it is often called chemical heat regulation. Heat transfer by the body surface to the external environment is called physical heat regulation.

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Heat is released by the body by conduction (convection), radiation (radiation) and evaporation of sweat.

When the ambient temperature is high, the heat release by the body of warm-blooded animals whose skin is almost devoid of sweat glands (for example, dogs) is additionally carried out by evaporation of sweat, as well as by evaporation of fluid from the surface of the respiratory tract. Finally, part of the heat is released from the body along with urine and feces .

If the processes of heat production prevail over the processes of heat transfer, overheating of the body occurs (see). If, on the contrary, heat transfer processes dominate over heat production processes, cooling occurs (see).

Both humoral and nervous mechanisms are involved in thermoregulation.

Temperature fluctuations in ambient air act on special receptor formations that are sensitive to changes in temperature (thermoreceptors). There are thermal and cold receptors . The excitation from thermoreceptors enters through special pathways to the brain and causes changes in the activity of the thermoregulation center located in the hypothalamus. The excitation of various parts of this center leads to a change in the processes of heat production and heat transfer. When the thermoregulation center is turned off with special chemicals, the body loses its ability to maintain constant temperature. In recent years, this feature has been used in the clinic for artificial cooling of the body during complex surgical operations on the heart .