Reflex action

In the syllabus and the exam

Reflex action is examined through the full pathway of the reflex arc, and candidates are expected to sequence and explain each stage rather than only stating the outcome. A complete answer names, in order, the receptor detecting the stimulus, the sensory neuron carrying the impulse to the spinal cord, the relay neuron within the spinal cord, the motor neuron carrying the impulse onward, and the effector, usually a muscle, that produces the response, alongside the key point that the pathway bypasses the brain so the response is faster than a voluntary action. Structured questions often use the knee-jerk reflex or the withdrawal reflex from a sharp or hot object as the scenario and ask candidates to explain why a reflex action is important for survival, with the expected answer centred on speed of protection against harm without needing conscious decision-making. A common error is stating that the brain controls a reflex action, when the defining feature examiners look for is precisely that the spinal cord, not the brain, coordinates the immediate response.

Example

Touching a hot pan triggers a reflex action that withdraws the hand before the pain is even consciously felt.

Related terms

NeuronSynapseStimulus

Source:SRC-DSKP-EN