Controlling Body Temperature

• The body has to keep its insides at a temperature of around 37 degrees celcius - the optimum temperature for enzymes in the body
• The body has to balance the amount of energy gained (e.g. by respiration) and lost to keep the core body temperature constant
• There is thermoregulatory centre in the brain, which contains receptors that are sensitive to the temperature of the blood flowing through the brain
• The thermoregulatory centre also receives impulses from temperature receptors in the skin, giving information about skin temperature
• Body temperature is controlled via negative feedback
• Too high:

  • temperature receptors detect that core body temperature is too high
  • the thermoregulatory centre acts as a coordination centre - it receives information from the temperature receptors and triggers the effectors automatically
  • effectors, e.g. sweat glands, produce a response and counteract the change
• Too low:

  • temperature receptors detect that core body temperature is too low
  • the thermoregulatory centre acts as a coordination centre - it receives information from the temperature receptors and triggers the effectors automatically
  • effectors, e.g. muscles, produce a response and counteract the change
• Some effectors work antagonistically, e.g. one effector heats and another cools - they'll work at the same time to achieve a very precise temperature
• Antagonistic effectors allow a more sensitive response
• Different responses are produced by effectors to counteract an increase or decrease in body temperature
• When you're too hot:

  • hairs lie flat
  • sweat is produced by sweat glands and evaporates from the skin
  • this transfers energy to the environment
  • the blood vessels supplying the skin dilate so more blood flows close to the surface of the skin - this is called vasodilation
  • this helps transfer energy from the skin to the environment
• Vasodilation

  blood vessels dilate (get wider) so more blood flows close to the surface of the skin
• When you're too cold:

  • hairs stand up to trap an insulating layer of air
  • no sweat is produced
  • blood vessels supplying skin capillaries constrict to close off the skin's blood supply - this is called vasoconstriction
• When you're cold you shiver too (muscles contract automatically), this needs respiration, which transfers some energy to warm the body
• Vasoconstriction

  blood vessels constrict (get narrower) to close off the skin's blood supply