Odors

Odors are the perceptual experiences produced by volatile chemical compounds when they interact with the olfactory system. They are detected by olfactory receptor neurons in the nasal cavity, which express a large family of G-protein-coupled receptors. Each odorant can bind to multiple receptor types, and each receptor can respond to multiple odorants, enabling a combinatorial code that allows the brain to distinguish many different smells. Odor perception depends on concentration, temperature, humidity, and context, and can decline with continuous exposure through adaptation.

The olfactory epithelium sends signals to the olfactory bulb, where initial processing occurs before higher brain regions interpret odor quality, intensity, and hedonic value. Unlike other senses, olfactory information often has a weak direct anatomical relay to the thalamus and may be integrated with memory and emotion in limbic areas.

Odors are described in terms of their qualitative character (aroma, scent, fragrance) and hedonic valence (pleasant, neutral, unpleasant). They arise from natural sources such as foods, flowers, and decaying matter, or from synthetic compounds used in flavorings, fragrances, and industrial applications.

Measurement and regulation of odors involve olfactometry to estimate odor concentration and nuisance; environmental monitoring may require odor thresholds and dispersion modeling. Odor detection and perception have practical implications for food flavor, product design, workplace safety, and environmental management.