# Explain how the endocrine system and the cardiovascular system are integrated to respond to a sudden stressful situation.

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

> When an organism perceives a threat, a coordinated whole-body response is initiated within seconds, preparing the body for rapid physical action.

## Mark scheme (4 marks)

1. The adrenal glands (medulla) secrete adrenaline into the blood in response to stress / sympathetic nervous stimulation.
2. Adrenaline travels via the blood to the heart and increases heart rate / cardiac output.
3. Adrenaline causes vasodilation of blood vessels supplying skeletal muscle / vasoconstriction of vessels supplying non-essential organs, redistributing blood flow.
4. The integrated response ensures more oxygen and glucose are delivered to muscles / tissues, enabling increased metabolic activity for the 'fight or flight' response.

## Key terms

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

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](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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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-endocrine-system-and-338337f9) · Published by Druglandscape Ltd.