# A person has been sitting in a very cold room for an extended period of time. Their core body temperature begins to fall below the normal set point. Explain how the body detects this change and the responses that help to return body temperature to the set point.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 4.6 Homeostasis · Explain · 5 marks

## Mark scheme (5 marks)

1. Thermoreceptors in the skin / hypothalamus detect the fall in temperature
2. The nervous system / hypothalamus sends a signal / nerve impulse to effectors
3. Shivering occurs — muscles contract rapidly, generating heat by respiration
4. Vasoconstriction occurs — blood vessels near the skin surface narrow / constrict, reducing heat loss from the blood
5. These responses return body temperature to the set point / normal level, maintaining a constant internal environment (homeostasis)

## Key terms

- [set point](https://www.gradenine.co.uk/glossary/set-point)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-person-has-been-sitting-in-d2d1387b) · Published by Druglandscape Ltd.