Body Temperature

• Body temperature must be kept constant at around 37 degrees, this is the optimum temperature for enzymes
• Body temperature is controled by the thermoregulatory centre in the brain, this contains receptors which are sensitive to blood temperature
• When the body is too hot

  • Hairs flatten
  • Sweat is produced and evaporates from the skin, this transfers energy to the environment
  • Blood vessels dilate so more blood flows close to the surface of the skin, this is calle vasodilation
  • Energy is transfered from the skin to the environment
• When you are too cold

  • Hairs stand up to create an insulating layer of air
  • No sweat is produced
  • Blood vessels constrict and close off the skin's blood supply, this is called vasoconstriction
  • Muscles automatically contract (shivering), this needs respiration which transfers energy to warm the body
• Some effectors work antagonistically, e.g. one effector heats when another cools. This creates a more sensitive response