Explain how the endocrine system responds when blood glucose concentration falls below the optimum level.

OCR GCSE Biology A: Gateway Science (J247) — B3.2 Coordination and control — the endocrine system · Explain · 4 marks · View as Markdown

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

During a long-distance run, a competitor's blood glucose concentration begins to drop significantly below the normal level.

Model answer (4 marks)

The pancreas senses the fall in blood glucose and releases glucagon.
Glucagon travels through the bloodstream to the liver.
In the liver, glucagon stimulates glycogenolysis, converting glycogen into glucose.
The released glucose returns the blood glucose level to normal, completing a negative‑feedback loop.

Examiner tips

  • Use the word ‘stimulates’ to show the action of glucagon on the liver. Mention the liver as the target organ to demonstrate organ specificity.

Common mistakes

  • Confusing insulin with glucagon. Forgetting to state that the liver is the target organ. Using vague terms like ‘hormone’ without naming glucagon.

Mark scheme (4 marks)

  1. The pancreas detects the fall in blood glucose concentration and secretes glucagon
  2. Glucagon is a hormone that travels in the bloodstream to target organs
  3. Glucagon causes the conversion of glycogen into glucose in the liver
  4. This raises blood glucose concentration back to the optimum level / this is an example of negative feedback

Key terms in this question

endocrine system

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