A person moves from a warm room into a cold environment. Explain how the body responds to maintain a constant internal temperature.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
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.
Model answer (5 marks)
Temperature receptors in the skin detect the drop in external temperature.
A signal is sent via the nervous system to the thermoregulatory centre in the hypothalamus.
The hypothalamus activates shivering – rapid muscle contractions that generate heat.
It also induces vasoconstriction of blood vessels near the skin surface, reducing heat loss.
These responses restore the core temperature to 37 °C, maintaining homeostasis.
A signal is sent via the nervous system to the thermoregulatory centre in the hypothalamus.
The hypothalamus activates shivering – rapid muscle contractions that generate heat.
It also induces vasoconstriction of blood vessels near the skin surface, reducing heat loss.
These responses restore the core temperature to 37 °C, maintaining homeostasis.
Examiner tips
- Use the exact terms: skin receptors, hypothalamus, shivering, vasoconstriction, homeostasis.
- Show the causal chain – receptor → brain → effect.
- Keep answer concise; each point counts as one mark.
Common mistakes
- Confusing skin temperature with core temperature; students say ‘core temperature drops’ instead of ‘skin temperature drops’.
- Using ‘respiration’ instead of ‘shivering’ to describe heat generation.
- Omitting the role of the hypothalamus or vasoconstriction.
Mark scheme (5 marks)
- Temperature receptors in the skin detect the drop in (external/skin) temperature
- A signal / nervous impulse is sent to the thermoregulatory centre in the brain (hypothalamus)
- Muscles shiver / contract rapidly to generate heat (by respiration)
- Vasoconstriction occurs — blood vessels (near the skin surface) narrow, reducing heat loss
- These responses maintain / restore body temperature to the normal level (37 °C) — this is homeostasis / maintaining a constant internal environment
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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