# A person moves from a warm room into a cold environment. Explain how the body responds to maintain a constant internal temperature.

> Pearson Edexcel A-Level Biology A (9BI0) — 4.6 Homeostasis · Explain · 5 marks

> The normal core body temperature is 37 °C. When a person steps outside on a cold winter's day, their skin temperature receptors detect the change in conditions and send signals to the brain.

## Mark scheme (5 marks)

1. Temperature receptors in the skin detect the drop in (external/skin) temperature
2. A signal / nervous impulse is sent to the thermoregulatory centre in the brain (hypothalamus)
3. Muscles shiver / contract rapidly to generate heat (by respiration)
4. Vasoconstriction occurs — blood vessels (near the skin surface) narrow, reducing heat loss
5. These responses maintain / restore body temperature to the normal level (37 °C) — this is homeostasis / maintaining a constant internal environment

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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