Explain how the body uses a negative feedback system to restore normal blood glucose levels after a person eats a meal containing a large amount of carbohydrates.

OCR GCSE Biology A: Gateway Science (J247) — B3.3 Maintaining internal environments · Explain · 4 marks · View as Markdown

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

After eating a large carbohydrate-rich meal, a person's blood glucose concentration rises above the normal level. The body must respond to restore the stable internal environment.

Model answer (4 marks)

1. The pancreas senses the increased blood glucose level.
2. It releases insulin into the bloodstream.
3. Insulin stimulates cells to take up glucose and convert it into glycogen for storage in liver and muscle, thereby lowering blood glucose.
4. This response opposes the initial rise, restoring the normal glucose concentration – a negative feedback loop.

Examiner tips

Use the exact terms: pancreas, insulin, glycogen, negative feedback.
Show the sequence: detection → hormone release → action → restoration.
Mention that the response reverses the original change.
Keep each point concise and directly linked to the scheme points.

Common mistakes

Confusing insulin with glucagon or omitting the pancreas as the sensor.
Failing to state that the response lowers glucose, not raises it.
Not explicitly stating that the system is negative feedback or that it restores homeostasis.

Mark scheme (4 marks)

The pancreas detects the rise in blood glucose concentration
The pancreas releases insulin into the bloodstream
Insulin causes glucose to be converted into glycogen (stored in the liver / muscles), lowering blood glucose concentration
This is a negative feedback system because the response reverses / opposes the original change, restoring the normal blood glucose level (homeostasis)

Key terms in this question

negative feedback system