Thermal homeostasis or thermoregulation - a physiological function that supports the human and animal body temperature constant (with slight variations) with the regulation of heat production and heat loss. Thermal homeostasis is part of homeostasis.

The normal temperature of the internal environment and its regulation

Normally, the temperature of the human brain, blood, and internal organs on the average about 37˚S with oscillations in one direction or in the other direction is not more than 1, 5 ° C. Changing the temperature of internal organs and blood of 2 - 2, 5 ° C of the average level is already causing disorders in humans. The temperature of the human body 42 - 43˚S and above shall be considered incompatible with life.

At high ambient temperatures, increase the rate of heat production of the body (for example, during muscular work) thermoregulation is performed by changing the amount of heat transfer. This process is called physical regulators.

Thermoregulation at higher ambient temperature

The main part of thermoregulation is vascular thermoregulation, which is a widening or narrowing of blood vessels in the skin, whereby the skin is supplied a greater or lesser volume of blood, and it is given to the heat from the internal organs, i.e. part of the heat generated as a result of metabolism.

The maximum expansion of the blood vessels of the skin of the state of maximum constriction increases the heat six times. Not all areas of the skin equivalent involved in thermoregulation. Large heat transfer possible from the hands - up to 60% of the total heat production, whereas the area of ​​the brushes is not more than 6% of the total area of ​​the skin. When physical work involving muscles are particularly important areas of the skin over the muscles working. Part of the blood rushes working muscles directly into the veins of these sections of the skin, which greatly facilitates the return of heat from the muscles.

Thermoregulation at normal ambient temperature

As we approach the ambient temperature to body temperature decreases the efficiency of vascular and heat regulation is replaced by the following reaction of physical thermoregulation - sweating. Sweating is a water seepage through the skin surface where it evaporates. This process is also called insensible perspiration. Through it absorbed about a fifth of the basic exchange of heat.

Insensible perspiration is not regulated and not very dependent on the ambient temperature. With the threat of overheating of the sympathetic nervous system simply activates the sweat glands in the skin. With vigorous functioning sweat glands secrete up to 1, 5 liters of sweat per hour and more.

Thermoregulation at low ambient temperature

When the ambient temperature decreases and the threat supercooling primarily and sweating stops occurs vasoconstriction skin. If the skin temperature continues to fall and the threat of hypothermia is not eliminated, it includes so-called chemical heat regulation - increasing heat production of the body due to special forms of contractile activity of skeletal muscles and increasing the physiological activity of other organs (eg, liver).

With a relatively weak cooling of the muscles in their apparent ease arise periodically single reduction of individual fibers - the so-called Thermo muscle tone, which can increase the body's heat production by 20 - 40%.

With further cooling occurs cold muscle tremors, which manifested periodic series of quick cuts. Of heat it will be increased by 2 - 3 times more. Thermo muscle tone and shivering when cooling is most clearly revealed in the muscles of the head, neck and shoulder girdle.

After a prolonged adaptation to the cold heat production of muscle contractions in the cold shivering thermoregulation and increases muscle tone of 1, 5 - 2 times. This process is stimulated by the stress hormone norepinephrine and thyroid hormone thyroxine.

Management of thermal homeostasis

Manage all your reactions that allow you to maintain a constant body temperature in different conditions, carried out by special nerve centers in the brain. The main center of thermoregulation is a part of the brain called the hypothalamus. Thermoregulatory centers are informed of the conductive paths from temperature sensitive nerve cells located in different parts of the central nervous system and the peripheral thermoreceptors located in the skin. After receiving and analyzing information hypothalamus "orders" for the inclusion of certain regulatory systems.

Thermal homeostasis - it is one of the most advanced general homeostatic mechanisms of the human body.

Galina Romanenko

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