What is thermoregulation in human? As we know that thermoregulation refers to control systems operate in organisms to cope with environmental stresses including temperature extremes. Lets discuss in detail thermoregulation in human are as under;
REGULATORY STRATEGIES | THERMOREGULATION IN HUMAN
Endothermic to maintain high temperature: Mammals including human maintain their high body temperature within a narrow range of about 36-38C, because of their endothermic characteristics. They regulate the rate of metabolic heat production and balancing it with the rate at which they gain or lose heat from the surroundings. The origin of endothermy in birdsand mammals have provided the opportunity to keep high metabolic rate and availability of energy round the clock, thus had acquired greater ability to adaptations and has assisted in much of their wider diversity and distribution in diversified regions of the earth.
Shivering thermogenesis: The rate of heat production is increased by increased muscle contraction by movements or shivering so called as shivering thermogenesis.
Non-shivering thermogenesis; Hormones trigger the heat production as do thyroid hormones and are termed as non-shivering thermogenesis.
Brown fat: Some mammals possess brown fat (adipose tissue), which is specialized for rapid heat production.
Evaporative cooling: In overproduction of heat it is. dissipated through exposed surfaces by increasing blood flow or the evaporative cooling. In mammals it is observed that skin has been adapted as the organ of thermoregulation.
REGULATORY MECHANISMS IN COLD TEMPERATURE
Mammals have various mechanisms that regulate heat exchange with their environment. Vasodilatation (expansion of blood vessel) and vasoconstriction (shrinkage of blood vessels) effect heat exchange and may contribute to regional temperature differences within an animal.
Human: On a cool day a human’s temperature may be several degrees lower in the arms and legs than in the trunk, where the most vital glands are situated. Human mostly rely on a layer of fat just beneath the skin as insulating material-against heat loss.
Land mammals: Most land mammals respond to cold by raising their furs thereby trapping the thicker layer of still air and it acts as good insulator between animal skin and the surroundings.
Marine mammals; Marine mammals such as whales and seals inhabit much colder water than their body temperature have a very thick layer of Insulting fat called as blubber just under the skin.
REGULATORY MECHANISMS IN WARM TEMPERATURE
Marine mammals: Marine mammals dispose off their excess heat into warm seas by large number of blood vessels in the outer layer of the skin This dissipates the heat from the skin surface.
Terrestrial mammals: In terrestrial mammals, the sweat gland activity and the evaporative cooling is the one of the major temperature reducing strategy. Panting, the evaporative cooling in the respiratory tract,’ is the other mechanism as represented in the dogs. Bats etc., use saliva and urine for evaporative cooling.
THERMOSTAT FUNCTION AND FEEDBACK CONTROLS IN HUMAN
Hypothalamus – homeostatic thermostat; The body temperature regulation in humans is based on complex homeostatic systems facilitated by feedback mechanisms. The homeostatic thermostat is present in the hypothalamus, a brain part. It responds to the changes in the temperature above and below a set point which is 370C.
Thermoreceptors: In case of increase in temperature above the set point, certain warm temperature sensitive thermoreceptors in skim hypothalamus and other parts of nervous systems send the signals to the system that increase the blood flow to the skin and also cause sweat gland activation and the sweat is evaporated for the cooling. Cold receptors: In cold temperature, the cold receptors send the pulses to hypothalamus to inhibit heat loss mechanisms and activate the heat conservation mechanisms. This includes constriction of superficial blood vessels and stimulating shivering and non shivering mechanisms.
Temperature in fever (Pyrexia) ; In bacterial and viral infections mainly, leukocytes increase in number.These pathogens and the blood cells produce chemicals called as pyrogens. Pyrogens displace the set point of hypothalamus above the normal point of 37C, Fever or high temperature helps in stimulating the protective mechanisms against the pathogens.