Solution – reflex action is a rapid and involuntary response to a stimulus .

Examples of reflex action are – in bright light the pupil of the changes in size .

                                                    Sucking reflex in infants

Reflex arc – it is a neural path which controls a reflex . It is made up of sensory neurons , spinal cord , motor neuron and muscles .

• signal from the stimulus is picked by the sensory neuron and taken to the spinal cord .
• spinal cord send a message via motor neuron
• signal is transmitted to the effector muscle by the motor neuron .