Chemical senses

Article By:

Pfaffmann, Carl Department of Psychology, Rockefeller University, New York, New York.

Last reviewed:April 2021

DOI:https://doi.org/10.1036/1097-8542.127700

Neural systems used for physiological reception of and response to chemical stimulation by excitation of specialized receptors. In vertebrates, the senses of smell (olfaction) and taste (gustation), along with the so-called common chemical sense, constitute the external chemical senses, as contrasted with such internal chemoreceptors as the carotid sinus detectors of carbon dioxide in blood, and glucose receptors of the brain and certain visceral organs. The olfactory cells of vertebrates, usually located in the olfactory mucosa of the upper nasal passages, are specialized neural elements that are responsive to chemicals in the vapor phase. The floral fragrance of roses and the putrid smell of hydrogen sulfide are two examples of human olfactory sensations. Taste buds of the oral cavity, especially the tongue, are composed of modified epithelial cells responsive to chemicals in solution (see illustration). Sweet, salty, sour, bitter, and umami (savory) are the basic taste qualities experienced by humans. In certain fish (for example, catfish), taste buds occur over the body surface and barbels. The aforementioned common chemical sense is composed of free nerve endings in the mucous membranes of the eye, nose, mouth, and digestive tract and is responsive to irritants or other chemicals in either the vapor or liquid phase. See also: Carotid body; Chemoreception; Nervous system (vertebrate); Neurobiology; Olfaction; Sensation; Sense organ; Taste

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