Explain how the body responds to a sustained rise in core body temperature, such as during prolonged exercise, to restore homeothermy.

IB DP Biology Higher Level (2023 syllabus) — D3.3 Homeostasis · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Thermoreceptors in the hypothalamus detect a rise in core temperature above the set point.
Vasodilation of superficial skin arterioles increases blood flow to the skin, enhancing heat loss by radiation and convection.
Sweat glands are stimulated to secrete sweat; evaporation of sweat from the skin removes latent heat.
These responses form a negative‑feedback loop: as core temperature falls back to the set point, the effector responses are reduced or stopped.

Examiner tips

  • Use the word "detect" for the receptor action and "stimulated" for the effector actions. Mention the negative‑feedback nature explicitly. Keep the answer concise – 4 points can be covered in 4 short sentences.

Common mistakes

  • Confusing the hypothalamus with peripheral thermoreceptors. Forgetting to state that the responses are part of a negative‑feedback loop. Using vague terms like "heat loss" without specifying radiation, convection or evaporation.

Mark scheme (4 marks)

  1. Thermoreceptors in the hypothalamus detect a rise in blood/core temperature above the set point
  2. Vasodilation of superficial/skin arterioles increases blood flow to the skin surface, increasing heat loss by radiation and convection
  3. Sweat glands are stimulated to secrete sweat; evaporation of sweat from the skin surface removes latent heat
  4. These responses constitute negative feedback: as core temperature returns to the set point, the effector responses are reduced/switched off

Key terms in this question

homeothermy

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