The sense organs contain receptors that are sensitive to stimuli.
The nervous system consists of the central nervous system - brain and spinal cord -and peripheral nerves. Nerve impulses travel through the axons of neurones - nerve cells. Reflex actions are fast, automatic and protective responses.
Human vision is binocular, which gives us a good perception of depth. Vision defects include short-sightedness, long-sightedness and colour blindness.