# A sprinter is waiting for the starting pistol to fire at the beginning of a race. When the sound reaches the sprinter's ears, a nerve impulse travels to the brain, which then sends signals to the muscles in the legs. Explain how the nervous system coordinates the sprinter's response to the starting pistol.

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

> A sprinter crouches at the start line, listening carefully for the starting pistol. The moment the pistol fires, the sprinter's legs push powerfully off the blocks.

## Mark scheme (5 marks)

1. The ear acts as a receptor, detecting the stimulus (sound of the pistol)
2. A nerve impulse / electrical signal is sent along sensory neurones to the brain / central nervous system (CNS)
3. The brain (CNS) processes the information and coordinates a response
4. A nerve impulse is sent along motor neurones from the brain / CNS to the muscles (effectors)
5. The muscles (effectors) contract / respond, causing movement

## 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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