Reflex action: is spontaneous or unconscious response of body to a stimulus. Receptors : are specialized cells that can transducer external stimulus into a nerveimpulse e.g.rods & cones of retina. Sensory nerve : is afferent nerve carrying nervous impulse from peripheral organ towards CNS e.g. optic nerve. Motor nerve : is efferent nerve carrying nervous impulse from CNS to peripheral organ e.g. occulomotor nerve.