control of body temperature

• body temperature is monitored and controlled by the thermoregulatory centre in the brain (located in the hypothalamus)
• the thermoregulatory centre has receptors that are sensitive to the temperature of blood and the skin contains temperature receptors sensitive to the temperature of air and sends nervous impulses to the thermoregulatory centre
• when body temperature is too high:

  • vasodilation occurs
  • where the blood vessels in the skin get wider and dilate so a greater volume of blood flows closer to the surface of the skin, meaning more heat radiates and is transferred to the environment
  • and sweat is produced from sweat glands, which evaporates off the surface of the skin, transferring heat to the environment
  • both these mechanisms cause a transfer of energy from the skin to the environment
• when body temperature is too low:

  • vasoconstriction occurs
  • where the blood vessels in the skin constrict and get more narrow which means blood flows further away from the surface of the skin, reducing heat loss from the body
  • sweating stops
  • skeletal muscles contract and relax (shivering) which generates heat
  • goosebumps trap and insulating layer of air, reducing heat loss