Reflex arc
Exam-ready definition
The nerve pathway of a reflex action: receptor → sensory neurone → relay neurone (in the spinal cord) → motor neurone → effector, producing a fast, automatic response that protects the body.
How this is marked
Sequencing questions are marked on the correct order and correct neurone names. 'Fast' and 'automatic/does not involve conscious thought' are the two description marks. Drawing arrows the wrong way along neurones is an instant lost mark.
In an exam answer
Describing a hand pulling off a hot object: 'The receptor detects heat; the impulse passes along sensory → relay → motor neurones to the muscle, which contracts. A reflex arc.'
Full topic guide: Coordination & response
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