A patient is admitted to hospital with a dangerously high core body temperature of 41 °C following prolonged exercise in hot conditions. Explain how negative feedback mechanisms would act to return the patient's core body temperature to the normal set point of 37 °C.

OCR A-Level Biology A (H420) — 5.1 Communication and homeostasis · Explain · 4 marks · View as Markdown

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

The hypothalamus acts as the thermoregulatory centre in humans, continuously monitoring blood temperature and coordinating responses through both nervous and hormonal pathways. Peripheral thermoreceptors in the skin also send afferent impulses to the hypothalamus.

Model answer (4 marks)

The hypothalamus senses the core temperature is above the set point of 37 °C.
1. It activates effectors that promote heat loss – sweat glands secrete sweat and skin arterioles dilate.
2. These responses increase heat dissipation, lowering core temperature.
3. As the temperature falls towards 37 °C the stimulus to the hypothalamus diminishes.
4. When the set point is reached the hypothalamus stops signalling the effectors, ending the corrective response.

Examiner tips

  • Use the word ‘activate’ for effectors, ‘promote heat loss’ for sweat and vasodilation, and show the sequence from detection to cessation.
  • Mention the set point explicitly to link to negative feedback.

Common mistakes

  • Failing to state the hypothalamus as the detector; or confusing the set point with the current temperature.
  • Not linking the cessation of the response to the return to the set point.

Mark scheme (4 marks)

  1. The hypothalamus detects that blood temperature is above the set point / above 37 °C
  2. Effectors are activated to promote heat loss — sweat glands increase sweat production and/or vasodilation of skin arterioles occurs
  3. The corrective responses reduce core body temperature back towards the set point of 37 °C
  4. Negative feedback is completed — once temperature returns to the set point, the hypothalamus no longer stimulates the effectors, so the corrective response is switched off

Key terms in this question

negative feedback · set point

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