# Explain how the body responds to a sudden drop in core body temperature, such as when a person enters cold water.

> IB DP Biology Standard Level (2023 syllabus) — D3.3 Homeostasis · Explain · 4 marks

## Mark scheme (4 marks)

1. Thermoreceptors in the skin / hypothalamus detect the fall in core body temperature
2. The hypothalamus acts as the control centre / thermostat and coordinates the response
3. Effectors are activated: vasoconstriction of skin arterioles reduces heat loss / shivering generates heat through muscle contraction
4. This is an example of negative feedback — once core temperature returns to the set point, the corrective responses are switched off

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
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