# Explain how the nervous system and endocrine system work together to produce the 'fight or flight' response when a person perceives a threat.

> OCR A-Level Biology A (H420) — 5.5 Plant and animal responses · Explain · 4 marks

> When an organism detects a sudden threat in its environment, a rapid, coordinated response is initiated that prepares the body for intense physical activity. This response involves both rapid nerve impulses and slower-acting chemical signals.

## Mark scheme (4 marks)

1. The hypothalamus or sympathetic nervous system sends nerve impulses to the adrenal medulla
2. The adrenal medulla releases adrenaline into the blood
3. Adrenaline binds to receptors on target organs, causing physiological changes that prepare the body for action
4. This demonstrates coordination between the two systems: the nervous system provides rapid initial signalling while the endocrine system provides a sustained response via adrenaline

## Key terms

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

## Related

- [Revision notes for OCR A-Level Biology A (H420)](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-nervous-system-and-6ac9acf5) · Published by Druglandscape Ltd.