A person goes for a long run on a hot day. During the run, their body temperature rises above the normal set point. Explain how the body responds to return body temperature to normal.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
During exercise, muscles release large amounts of heat energy as a by-product of increased respiration. The body must maintain a constant internal temperature of approximately 37 °C.
Model answer (5 marks)
1. Thermoreceptors in the skin and in the hypothalamus detect the rise in body temperature above the set point.
2. The hypothalamus sends a nervous impulse to effectors in the skin.
3. Sweat glands produce more sweat, which evaporates from the skin surface, removing heat energy.
4. Vasodilation occurs – blood vessels near the skin surface widen, increasing blood flow to the skin so more heat is lost to the surroundings.
5. This is an example of negative feedback – the response reduces the change and returns body temperature back to the set point / normal level.
2. The hypothalamus sends a nervous impulse to effectors in the skin.
3. Sweat glands produce more sweat, which evaporates from the skin surface, removing heat energy.
4. Vasodilation occurs – blood vessels near the skin surface widen, increasing blood flow to the skin so more heat is lost to the surroundings.
5. This is an example of negative feedback – the response reduces the change and returns body temperature back to the set point / normal level.
Examiner tips
- Use the exact terminology (thermoreceptors, hypothalamus, sweat glands, vasodilation, negative feedback).
- Show the causal chain: detection → signal → effectors → outcome.
- Include the word ‘set point’ to demonstrate understanding of homeostasis.
Common mistakes
- Mixing up the direction of the signal (e.g., saying the skin sends the signal to the hypothalamus).
- Omitting the negative feedback element or not linking it to the response.
Mark scheme (5 marks)
- Thermoreceptors / receptors in the skin and/or hypothalamus detect the rise in body temperature above the set point
- A signal / nervous impulse is sent from the hypothalamus to effectors in the skin
- Sweat glands produce more sweat, which evaporates from the skin surface, removing heat energy
- Vasodilation occurs — blood vessels near the skin surface widen, increasing blood flow to the skin so more heat is lost to the surroundings
- This is an example of negative feedback — the response reduces the change and returns body temperature back to the set point / normal level
Key terms in this question
Related
- All Edexcel A-Level Biology A: Salters-Nuffield (9BN0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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