Thermoregulation — AQA GCSE Biology (Separate / Higher)
Thermoregulation is the control of body temperature. Humans maintain a core temperature of about 37 °C, the optimum for enzymes.
The control centre
Body temperature is monitored and controlled by the thermoregulatory centre in the brain (hypothalamus), which contains receptors sensitive to the temperature of the blood. Temperature receptors in the skin also send impulses to the centre.
When the body is too hot
- Vasodilation — blood vessels supplying the skin capillaries widen, so more blood flows near the surface and more heat is lost to the surroundings.
- Sweating — sweat glands release sweat; as it evaporates, it transfers energy from the skin, cooling the body.
When the body is too cold
- Vasoconstriction — skin blood vessels narrow, so less blood flows near the surface and less heat is lost.
- Shivering — muscles contract rapidly; this respiration releases heat.
- Sweating stops.
- (Hairs stand up to trap an insulating layer of air.)
Negative feedback
Thermoregulation is another example of negative feedback — a change in temperature triggers responses that reverse the change and restore 37 °C.
Exam tips
- The hypothalamus (thermoregulatory centre) controls temperature.
- Too hot → vasodilation and sweating; too cold → vasoconstriction, shivering, hairs raised.
- Note: blood vessels don't "move" — the vessels widen or narrow (vasodilation/vasoconstriction).
- Explain it as negative feedback.