Example 1
Core temperature rises from 37.0 to 38.2∘C. Find the change.
Change =38.2−37.0=+1.2∘C. A heat-loss response acts against this rise.
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Year 12 · SACE Stage 2
Thermoregulation
Practise heat-loss responses and negative-feedback directions.
Method and worked examples
Temperature affects enzyme activity and cellular function, so human thermoregulation coordinates heat production and heat transfer. Temperature receptors in the body and skin provide information to centres including the hypothalamus. When body temperature rises, increased skin blood flow and sweating can promote heat loss. Evaporation of sweat removes heat; sweating is less effective when evaporation is restricted.
When temperature falls, reduced skin blood flow can limit heat transfer, while shivering increases muscle activity and heat production. Behavioural responses such as seeking shade or adding clothing also affect heat balance. Vasodilation and vasoconstriction change blood flow near the skin; they do not move blood outside vessels. In a negative-feedback description, name the disturbance, relevant effector and opposing response.
Example 1
Example 2
Why does shivering oppose a fall in body temperature?
Repeated muscle contractions increase metabolic heat production, helping reduce the downward temperature disturbance.
Watch out: Evaporation is the major cooling step; restricted evaporation reduces cooling.