Homiotherms are generally known as warm-blooded animals (mammals). They have constant body temperature. They maintain their body temperature despite the change in atmospheric temperature. The normal range of temperature in mammals is 36-38 C. the regulatory mechanism includes both loss and conservation of heat. In some mammals, temperature regulates by specialized fat called brown fat. This brown fat is found in the neck and between the shoulders. This type of fat is responsible for the heat production for the body.

A- Mechanism of Thermoregulation in Cold Temperature:

This includes means i.e., physiological and behavioral.


  1. a) Non-Shivering Thermo genesis
  2. i) Eraction of hair:

Hairs of animals are raised to an almost vertical position due to the contraction of erector pili muscles in the skin. In furry animals, the hair in vertical position can trap a thick layer of satisfactory air next to the skin. Due to this, heat loss from the skin is reduced.

  1. ii) Reduction in blood flow towards skin:

The blood all around transports the heat in the body. In cold temperature, the narrowing of the blood arteriole or vaso-constriction occurs so the lesser blood is supplied towards the body surface to conserve the body heat. This is more marked in the limbs than in the rest of the body.

iii) Subcutaneous fat accumulation:

In mammals, fat is stored in adipose tissues below the skin. It is a bad heat conductor so it serves as a means of conserving heat. This is particularly very important for the survival of aquatic mammals like seals, whales, walrus, etc. However, in terrestrial mammals, which remain active in cooler season, fats are primarily stored as reserved food.


  1. b) Shivering Thermo genesis

In cooled condition, the muscle tone, initially under nervous control, tend to rise. If the cooled continues, shivering begins which generates heat in muscles. Under persistent cooler conditions, the basal metabolic rate (BMR) is raised in short term by the secretion of hormone called Adrenaline and in longer term by the secretion of another hormone, Thyroxin (T4) from thyroid gland.


Behavioral mechanism includes moving to a warmer location; huddling close together with other individuals; and in humans, putting on conditional clothes.


B- Mechanism of Thermoregulation in Hot Temperature:

It includes both physiological and behavioral mechanisms:


Few of these mechanisms include:

  • Lowering of hair growth which reduces the insulating effects.
  • Reduction in subcutaneous fats.
  • Evaporative cooling effect by means of secretion of sweat from skin.
  • Vasodilation of arterioles of skin promotes heat loss by flowing of blood to the skin.
  • Few animals losing heat from mouth, tongue, and respiratory passage.
  • Low metabolic rate also helps in the reduction of heat.



It involves migration or moving of animals from hotter location to a cooler location and the use of thin clothes specifically by human.


See Also