Q.Explain the mechanism of reflex action with the help of a suitable diagram.

In a reflex action, a receptor detects the stimulus, a sensory neuron carries the impulse to the spinal cord, a relay neuron there passes it to a motor neuron, which carries it to an effector (muscle/gland) — this ref...

Reflex arc: receptor -> sensory neuron -> spinal-cord relay neuron -> motor neuron -> effector, all without waiting for the brain.

A reflex action is a rapid, automatic (involuntary) response of the body to a stimulus, occurring without conscious control or the direct, initial involvement of the brain, mediated by a pathway called the reflex arc. Sequence: a Receptor (e.g. a pain or touch receptor in the skin) detects the stimulus (e.g. touching a hot object) and generates a nerve impulse. This impulse travels along a Sensory (afferent) neuron to the spinal cord. Inside the grey matter of the spinal cord, the sensory neuron synapses with a Relay neuron (interneuron/association neuron), which processes and relays the impulse directly to a Motor (efferent) neuron, without the signal first travelling up to the brain. The motor neuron carries the impulse out to an Effector organ — typically a muscle — causing it to contract (e.g. rapid withdrawal of the hand from the hot object), or a gland to secrete. Because the decision-making/relay happens at the spinal cord rather than requiring a round-trip to the brain, reflex actions are extremely quick, protecting the body from harm; a parallel ner …