Explain how the body responds to prevent overheating when core body temperature rises above the normal level.

WJEC GCSE Biology (Wales) — 2.5.3 Homeostasis · Explain · 4 marks · View as Markdown

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

During intense exercise, the body generates a large amount of heat. The body must detect this change and respond to return temperature to normal.

Model answer (4 marks)

Thermoreceptors in the skin and in the hypothalamus sense the rise in core temperature. The hypothalamus then signals the sympathetic nervous system to increase sweat gland activity, so more sweat is secreted onto the skin surface. The sweat evaporates, taking heat energy with it and thereby cooling the body. At the same time, blood vessels close to the skin dilate, allowing more blood to reach the surface and increasing heat loss by radiation and convection.

Examiner tips

  • Mention both skin and hypothalamic thermoreceptors; link to sympathetic output
  • Explain evaporation as heat removal and vasodilation as increased surface blood flow
  • Use correct terminology: sweat glands, vasodilation, sympathetic nervous system

Common mistakes

  • Confusing the role of the hypothalamus with the skin alone; not mentioning evaporation; using 'conduction' instead of 'evaporation' for sweat removal

Mark scheme (4 marks)

  1. Thermoreceptors / temperature receptors in the skin or hypothalamus detect the rise in temperature
  2. Sweat glands produce / secrete more sweat onto the skin surface
  3. Sweat evaporates from the skin, removing heat energy / cooling the body
  4. Blood vessels near the skin surface vasodilate / widen, allowing more blood to flow near the surface, increasing heat loss

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