Reflex action is a spontaneous rapid motor response to a stimulus. A simple reflex action consists of 5 components— 1. Receptor (Responds to stimulus). 2. Sensory neuron (Receptor to axon & transmits impulse). 3. Integration center (sensory impulse to motor impulse). 4. Motor neuron (efferent impulses from integration Centre). 5. An Effector responds (glands, muscles) Hence, the sequence of events in a reflex action are → Receptor → sensory neuron → CNS → motor neuron → effector responds.