A runner completes a long-distance race on a hot day. During the race, the runner's core body temperature rises above the normal set point. Explain how the body responds to return the core body temperature to the set point.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
During intense exercise, muscles generate large amounts of thermal energy. The nervous system detects changes in body temperature and coordinates responses to restore normal conditions.
Model answer (5 marks)
Thermoreceptors in the hypothalamus detect the rise in core body temperature above the set point.
Vasodilation occurs – arterioles near the skin surface widen, allowing more blood to reach the skin.
The increased blood flow to the skin transfers more thermal energy to the environment by radiation.
Sweat glands produce and release more sweat onto the skin surface.
The sweat evaporates from the skin, removing heat from the body and cooling it back to the set point.
Vasodilation occurs – arterioles near the skin surface widen, allowing more blood to reach the skin.
The increased blood flow to the skin transfers more thermal energy to the environment by radiation.
Sweat glands produce and release more sweat onto the skin surface.
The sweat evaporates from the skin, removing heat from the body and cooling it back to the set point.
Examiner tips
- Use the exact terms: thermoreceptors, hypothalamus, vasodilation, arterioles, radiation, sweat glands, evaporation.
- Show the sequence of events – detection, vasodilation, blood flow, radiation, sweating, evaporation.
- Keep each point brief but complete – 5 points, 1 mark each.
Common mistakes
- Confusing skin temperature with core temperature; the set point is core. Using ‘conduction’ instead of ‘radiation’ for heat loss. Omitting the role of the hypothalamic thermoreceptors or the evaporation step.
Mark scheme (5 marks)
- Thermoreceptors in the hypothalamus detect the rise in core body temperature above the set point
- Vasodilation occurs — blood vessels (arterioles) near the skin surface widen / dilate
- More blood flows to the skin surface, so more thermal energy is transferred to the environment / lost by radiation
- Sweat glands produce / release more sweat onto the skin surface
- Sweat evaporates from the skin surface, which transfers thermal energy away from the body / cools the body
Key terms in this question
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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