Olfaction

Olfaction is the sense of smell, produced when sensory systems detect airborne chemical molecules. It supports odor identification, food evaluation, hazard detection, and social communication.

Olfactory epithelium: A specialized nasal tissue containing olfactory sensory neurons and supporting cells. It is where inhaled odor molecules first interact with smell receptors.
Odorant: A volatile chemical molecule capable of stimulating olfactory receptors. Odorants are the airborne chemicals that initiate olfactory perception.
Flavor: The combined sensory experience of taste, smell, and other oral sensations during eating and drinking. Retronasal smell supplies much of what is experienced as food flavor.
Taste: The sense that detects dissolved chemicals through receptors in the mouth, especially on the tongue. Taste detects chemicals in solution, while olfaction detects airborne molecules.
Olfactory receptor: A protein that binds odorants and initiates signaling in an olfactory sensory neuron. Different receptor proteins detect different features of airborne chemicals.
Volatility: A substance’s tendency to enter the gas phase under specified conditions. A molecule must become airborne to reach olfactory receptors through ordinary smelling.
Retronasal olfaction: Olfactory perception produced when volatile compounds travel from the mouth to the nasal cavity during eating. It explains why foods lose much of their flavor when nasal airflow is blocked.
Trigeminal sensation: Chemical or mechanical sensations conveyed by the trigeminal nerve, including pungency, cooling, and irritation. Many apparent smells also trigger nasal sensations that are not olfactory.
Olfactory transduction: The conversion of odorant binding into electrical signals in olfactory sensory neurons. This process turns chemical contact into neural activity.
Chemoreception: The detection of chemical stimuli by specialized sensory systems. Olfaction is one form of chemical sensing.

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