From Big Medical Encyclopedia

HEAT PRODUCTION (synonym heat generation) — formation of warmth in fabrics and bodies as a result of the work made in a live organism. It includes the work performed for maintenance of structural integrity and life activity of an organism; work of reduction of cross-striped and unstriated muscles; work on movement of ions against a gradient of their concentration in a cellular membrane, necessary for preservation of excitability of a cell; the work of synthesis of various organic compounds connected with continuous updating of cellular structures, formation of secrets, hormones, enzymes, etc. All these types of work are made in an organism due to chemical energy of hydrolysis of makroergichesky connections (see. Vysokoergichesky connections ) — ATP, creatine phosphate, etc. — synthesis to-rykh occurs due to free energy of the ingredients of food which are split in the course of a metabolism. At this synthesis apprx. 40% of energy turns into heat and dissipates in fabrics. Further during the use of makroergichesky connections for performance of work of 40 — 50% of chemical energy of their hydrolysis it is also lost in the form of heat. As a result of efficiency of the specified types of work makes only 20 — 10%.

In the conditions of standard metabolism (see) when external work as an organism is not made, all power turning into an organism comes to an end with heat generation. At reductions of a cardiac muscle, e.g., about 80 — 90% of all energy consumed by heart immediately pass in warmly respectively a size efficiency of mechanical work of a cardiac muscle. Other 10 — 20% of potreblyaekhmy energy turn into a motive energy of moving blood, completely turns edges into heat within one cycle of blood circulation as a result of friction of blood about walls of blood vessels. For this reason in the conditions of standard metabolism or muscular rest size T. is the most exact measure of total power consumption an organism. The method of a direct calorimetry is based on this principle (see. Calorimetry ).

In a condition of muscular rest falls to the share of a brain apprx. 20% of all T., about 50 its % fall to the share of internals, other amount of heat — on a share of muscles, skin and other fabrics. During the muscular work of T. an organism can increase by 5 — 10 times and more. In the reduced muscle distinguish initial T., (late) T consisting of an activation heat and warmth of shortening, and set aside. The activation heat represents heat effect of those chemical processes, to-rye transfer a muscle from an unexcited state to active. Warmth of shortening is formed as a result of the process of reduction. The set aside T. it is connected with work of resynthesis of the makroergichesky connections spent in the course of muscular contraction. At action of cold of T. an organism increases at the expense of a thermoregulatory muscle tone (see. Thermal control ) and Cold muscular shiver, adjustable c. N of page. After adaptation to cold of T. muscular contractions increases in result of specific reorganization of power of muscle cells and influences of noradrenaline. Therefore the organisms adapted to cold can sharply increase T. at the expense of rather very weak thermoregulatory tone or a weak Cold muscular shiver. Important source of additional T. at animals brown fatty tissue is, weight a cut increases io to a measure of adaptation to cold.

T. increases at specifically dynamic effect of food (see. Metabolism and energy ), under the influence of nek-ry substances (2,4 - alpha dinitrophenol, polypeptides, etc.), at various diseases as a result of development of a feverish state (see. Fever ), hyperfunctions of a thyroid gland.

Bibliography: Bazhenov Yu. I. Thermogenesis and muscle performance at adaptation to cold, L., 1981; D about l N and to V. R. Bioenergetika of modern animals and an origin of a gomoyotermnost, Zhurn., general biol., t. 42, No. 1, page 60, 1981; II in An about in K. P. Bioenergetik and a temperature homeostasis, L., 1972; P e in z N e r L. Fundamentals of bio-energetics, the lane with English, M., 1977; X and with to and V. V. Energetik's N of heat generation and adaptation to cold, Novosibirsk, 1975; In 1 i g h J. Temperature regulation in mammals and other vertebrates, Amsterdam a. o., 1973; Hill A. V. Work and heat in a muscle twitch, Proc. roy. Soc. B, v. 136, p. 220, 1949.

K. P. Ivanov.