CHAPTER 28. THERMOREGULATION

28.1 General characteristics of thermoreguIa-tion

28.2 Heat generation

28.3 Heat transfer

28.4 Functional thermoregulation

Profile materials Control questions Situational tasks

28.1. General characteristics of thermoregulation

There are 3 types of organisms according to their ability to maintain a constant body temperature.

Poikilotherms (cold-blooded) are animals and insects whose body temperature fluctuates in tune with the ambient temperature. To increase body temperature, they use external heat sources and their bodies usually have high thermal conductivity.

Homeotherms (warm-blooded) are people, higher vertebrate animals, and birds. They are capable of isothermal regulation: maintaining a constant temperature at the ?core? of their bodies. In humans the temperature is maintained at 36.9-37.1 °С, even with significant fluctuations in the temperature of the environment. They have powerful internal heat sources and better thermal insulation of the body.

Heterotherms are animals with daily or seasonal deviations of the ?core? when the temperature varies by more than ±0.5 °С; it is characteristic of hibernating animals and some birds. In humans, heterothermia is characteristic for newborns and adults in REM sleep.

Role of homeothermy in evolution

• rate of enzymatic reactions and metabolism;

• phase state of membrane lipids (liquid or crystalline) and the functional state of membrane proteins: receptors, channels, and enzymes;

• the rate of formation and stability of bonds in the complexes: hormone - receptor, mediator - receptor, antigen - antibody, activity of ion channels, etc.;

• organ functions; central nervous system excitability, skeletal muscle and myocardial contractility.