Vision: rod and cone cells of the eye’s retina are specialized to respond to the electromagnetic radiation of light.
Hearing: the ear’s receptor neurons are topped by hair bundles that move in response to the vibrations of sound.
Smell: olfactory neurons at the back of the nose respond to odorant chemicals that bind to them.
Taste: receptor cells on the tongue and the back of the mouth respond to chemical substances that bind to them.
Touch: Meissner’s corpuscles are specialized for rapid response to touch, while free nerve endings bring sensations of pain.
—Source: Illustration, Eade Creative Services Inc. / George Eade illustrator (rod and cone cells adapted from Scientific American Vol. 256, No. 2, page 42, 1987). Edited by Dr. Hugo Heyrman.