An action is an involuntary response to a stimulus. A reflex is made possible by a neural pathway called the reflex arc. Whenever a sense organ senses any danger (stimulus). The sensory neurons pick up signals from the sensory organ and send them to the spinal cord. It is then received by the neurons in the spinal cord. The spinal cord then sends back signals to the muscle through the motor neuron. The muscles (effector organ) attached to the sense organ move the organ away from danger.
