# A student accidentally touches a very hot pan. Before the student is consciously aware of the pain, their hand has already been pulled away. Explain how the nervous system brings about this rapid, automatic response.

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

> When a person touches something painfully hot, a protective response occurs almost instantly — faster than conscious thought.

## Mark scheme (5 marks)

1. The heat acts as a stimulus, detected by a receptor in the skin
2. A nerve impulse is sent along a sensory neurone to the spinal cord (relay neurone)
3. The relay neurone in the spinal cord connects the sensory neurone to the motor neurone
4. The impulse travels along a motor neurone to the effector (muscle)
5. The response is a reflex action — it is rapid and automatic because it bypasses the brain / does not require conscious thought

## 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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