# Explain how the endocrine system uses negative feedback to return blood glucose concentration to its optimum level after a person goes for a long run.

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

> During a long run, muscles use glucose rapidly for respiration, causing blood glucose concentration to fall below its optimum level. The endocrine system detects this change and responds to restore balance.

## Mark scheme (4 marks)

1. The pancreas detects the fall in blood glucose concentration and releases glucagon into the bloodstream.
2. Glucagon causes glycogen to be converted into glucose (in the liver).
3. This raises / increases blood glucose concentration back towards the optimum level.
4. This is an example of negative feedback because the response reverses / opposes the original change (fall in blood glucose).

## Key terms

- [endocrine system](https://www.gradenine.co.uk/glossary/endocrine-system)

## Related

- [Revision notes for OCR GCSE Biology A: Gateway Science (J247)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-endocrine-system-uses-764aad49) · Published by Druglandscape Ltd.