# A athlete is preparing for a marathon. During training, their blood glucose levels drop significantly. Explain how the body responds to low blood glucose levels to restore them to normal, and describe why this method of communication is suited to coordinating a whole-body response.

> OCR A-Level Biology B — Advancing Biology (H422) — 5.8 Hormonal communication · Explain · 5 marks

> During prolonged exercise, muscles use glucose rapidly as a respiratory substrate. The blood glucose concentration can fall well below the normal range. The body must detect this change and respond to restore balance.

## Mark scheme (5 marks)

1. The pancreas detects the fall in blood glucose concentration
2. The pancreas releases glucagon (a hormone) into the blood
3. Glucagon travels in the blood to the liver (target organ)
4. The liver converts glycogen back into glucose (glycogen is broken down), raising blood glucose back to normal
5. Hormones are suited to a whole-body response because they travel in the blood and can reach all organs / act on multiple target organs simultaneously / the response is sustained over a longer period compared to nervous communication

## Related

- [Revision notes for OCR A-Level Biology B — Advancing Biology (H422)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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