4) Control of body temperature

• . Human body temperature should be kept at around 37℃.
• · This gives an optimum temperature for enzymes to work.
• . The thermoregulatory centre in the brain:

  monitors and controls body temperature

  has receptors that monitor the temperature of the blood flowing

  through the brain

  • receives information (impulses) from temperature receptors in the

  skin.
• . If the body temperature is too high:

  blood vessels widen, directing more blood to the surface of the skin -

  this is called vasodilation

  more sweat is produced from the sweat glands and evaporates

  • both these mechanisms cause a transfer of energy from the skin to

  the environment.
• . If the body temperature is too low:

  blood vessels narrow, directing blood away from the surface of the

  skin - this is called vasoconstriction

  sweating stops

  • skeletal muscles uncontrollably contract and relax quickly (shiver),

  which transfers more heat to the blood.