# Explain how the nervous system and the endocrine system are integrated during the fight-or-flight response to produce coordinated physiological changes in the body.

> IB DP Biology Higher Level (2023 syllabus) — C3.1 Integration of body systems · Explain · 4 marks

## Mark scheme (4 marks)

1. The hypothalamus detects a stressor and activates the sympathetic nervous system, which directly stimulates the adrenal medulla.
2. The adrenal medulla secretes adrenaline (epinephrine) into the blood, representing the endocrine component of the response.
3. Adrenaline binds to receptors on target organs, producing rapid, widespread effects such as increased heart rate, dilation of bronchioles, or redirection of blood flow to skeletal muscle.
4. Integration is achieved because the nervous system provides rapid, short-duration, localised signals whereas the endocrine system provides slower, sustained, widespread effects, allowing the body to respond both immediately and over a prolonged period.

## Key terms

- [fight-or-flight response](https://www.gradenine.co.uk/glossary/fight-or-flight-response)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](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-dda4a24b) · Published by Druglandscape Ltd.