# Explain how the pupil reflex protects the eye when a person moves from a dark room into bright light. Include the structures involved and the type of response produced.

> AQA A-Level Biology (7402) — 3.6.1 Stimuli and Responses · Explain · 5 marks

## Mark scheme (5 marks)

1. Bright light is the stimulus detected by receptors in the eye (retina)
2. A nerve impulse is sent along a sensory neurone to the brain (coordinator)
3. Motor neurone carries impulse to the iris (effector / circular muscles of the iris)
4. Circular muscles of the iris contract, causing the pupil to constrict / become smaller
5. This is an automatic / involuntary response that protects the eye by reducing the amount of light entering / preventing damage to the retina

## Key terms

- [reflex](https://www.gradenine.co.uk/glossary/reflex)
- [pupil](https://www.gradenine.co.uk/glossary/pupil)

## Related

- [Revision notes for AQA A-Level Biology (7402)](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-pupil-reflex-protects-ae5b7e91) · Published by Druglandscape Ltd.