Olfaction (smell) and gustation (taste) are called chemical senses because they rely on sensory receptors known as chemoreceptors that respond specifically to chemical molecules. Olfaction detects volatile chemical molecules in the air, which interact with receptors in the nasal cavity, while gustation detects chemical compounds in food and drinks through receptors on the tongue's taste buds. The interaction of these chemical molecules with their respective receptors generates neural signals that the brain interprets as distinct smells or tastes. Unlike other senses that respond to physical stimuli like light or sound waves, olfaction and gustation fundamentally depend on chemical stimuli, hence the name chemical senses.