The senses of smell, taste, sight, hearing, and balance are associated with very specialized, localized sensory receptors. The sensations of smell and taste are closely related, both structurally and func-tionally, and both are initiated by the interaction of chemicals with sensory receptors. The sense of vision is initiated by the interac-tion of light with sensory receptors. Both hearing and balance function in response to the interaction of mechanical stimuli with sensory receptors. Hearing occurs in response to sound waves, and balance occurs in response to gravity or motion.