# A student is working in a laboratory and accidentally knocks a glass beaker. Without thinking, they quickly blink and flinch away before the beaker hits their face. Explain why the student responds so rapidly, describing the roles of the receptor, coordinator, and effector in this reflex action.

> Pearson Edexcel A-Level Biology A (9BI0) — 4.3 Nervous system and reflex action · Explain · 5 marks

> Reflex actions are rapid, automatic responses to stimuli that do not require conscious thought. They are coordinated through a reflex arc involving specific types of neurones.

## Mark scheme (5 marks)

1. A receptor detects the stimulus (the approaching beaker / light stimulus / sudden movement)
2. A sensory neurone carries the electrical impulse from the receptor to the spinal cord / coordinator
3. The spinal cord acts as the coordinator / relay neurone in the spinal cord passes the impulse to the motor neurone
4. A motor neurone carries the impulse from the spinal cord to the effector (muscle)
5. The response is rapid because the impulse bypasses the brain / does not require conscious thought / shorter pathway means faster response

## Key terms

- [receptor](https://www.gradenine.co.uk/glossary/receptor)
- [coordinator](https://www.gradenine.co.uk/glossary/coordinator)
- [effector](https://www.gradenine.co.uk/glossary/effector)

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](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/a-student-is-working-in-a-d2f45084) · Published by Druglandscape Ltd.