# Reflex arc

A fast, automatic response to a stimulus that does not need conscious thought.

Biology (school) · Part 03: The human body · Card 8 of 11 · Last updated 2026-10-19

## Analogy

A shortcut: the signal goes via the spinal cord, not the brain.

## In practice

You pull your hand away from a hot pan before you feel the pain.

## Practice

### Flashcards

- **What is the path of a reflex arc?** Receptor, sensory neurone, spinal cord, motor neurone, effector.

### Interview questions

**Describe the route of a reflex action.**

- A receptor detects the stimulus
- A sensory neurone carries the signal to the spinal cord
- A relay neurone passes it on
- A motor neurone sends it to an effector that responds

## Questions people ask

### Why are reflexes faster than normal actions?

In a reflex, the signal travels from the sensory neurone to the spinal cord and straight out via a motor neurone, without going through the brain's decision-making. The shorter route saves time, which helps protect you from harm, such as when you touch something dangerously hot.

### What is a synapse?

A synapse is the tiny gap between two nerve cells. The electrical signal cannot jump across, so the first nerve cell releases chemicals that cross the gap and trigger a new electrical signal in the next cell. This one-way chemical step is why signals travel in only one direction.

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