5. Temperature Regulation in the Human Body

5.1 Heat loss in the body

• Heat is lost from the body by (i) evaporation of sweat (ii) through the skin by conduction, convection and radiation (iii) urination and (iv) defaecation.

5.2 Heat gain by the body

• Heat is produced within body as a result of metabolic activities such as tissue respiration.

• Tissue respiration generates energy in the form of ATP. At the same time, heat is released.

5.3 Thermoregulation

• Changes in external temperature (stimulus) are detected by temperature receptors on the skin.

• The information is then sent to the hypothalamus.

• Thermoreceptors of the hypothalamus also monitors the temperature of blood passing through it.

• Hypothalamus in the brain then regulates body temperature.

When there is an increase in temperature

• Skin arterioles dilate and more blood flows through the skin surface. More heat is lost by conduction, convection and radiation.

• Sweat glands become more active – More sweat is produced. Evaporation of sweat leads to removal of latent heat of vaporisation from the body.

• Rapid breathing which releases heat. Decrease in metabolic rate causing less heat to be produced within body.

When there is a decrease in temperature

• Arterioles constrict. Less blood flows through the skin capillaries. Less heat is lost by conduction, convection and radiation.

• Sweat glands become less active – Less sweat is produced.

• Metabolic rate increases to produce more heat. Shivering in the form of increased muscular contractions generate more heat and raises body temperature to normal.