What is reflex action? Explain the mechanism of reflex action with a suitable example.

Reflex Action: It is an automatic nerve mediated response to a stimulus without consulting the will of the individual, e.g., withdrawal of hand on being pricked or coming in contact with hot surface.

Mechanism: The stimulus for reflex action is picked up by a receptor located in the organ on which stimulus is acting. One or more sensory neurons carry the impulse from receptor to the central nervous system (e.g., spinal cord). CNS functions as modulator. It transfers the sensory nerve impulse to one or more motor neurons. The motor neurons carry the impulse to effectors which provide a proper response to the stimulus.

Stimulus → Receptor → Sensory neurons → CNS → Motor neurons → Effectors → Response.