# A student is studying how the nervous system coordinates a response. They learn that when a person smells smoke, the nervous system detects the stimulus and sends electrical impulses to the muscles, which contract to move the person away from danger. Explain how the nervous system coordinates this response, from detecting the stimulus to bringing about the muscular response.

> OCR A-Level Biology B — Advancing Biology (H422) — 5.7 Nervous communication · Explain · 5 marks

> When a person smells smoke, receptor cells in the nose detect the chemical stimulus. A series of electrical impulses then travel through the nervous system until muscles contract, moving the person away from danger.

## Mark scheme (5 marks)

1. Receptor cells in the nose detect the stimulus (smell of smoke)
2. Electrical impulses travel along sensory neurones to the central nervous system (CNS / brain or spinal cord)
3. The CNS (brain) processes the information and coordinates the response
4. Electrical impulses travel along motor neurones from the CNS to the effector (muscle)
5. The muscle (effector) contracts, bringing about the response / moving the person away from danger

## Related

- [Revision notes for OCR A-Level Biology B — Advancing Biology (H422)](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-studying-how-the-98f36450) · Published by Druglandscape Ltd.