People can discern thousands of odors, although there is great variability among people in the ability to detect particular odors. Some of the differences in this detection ability are believed to be genetically determined.
Odor is a sensation, a stimulus and perception captured by the sense of smell by the interaction of an organic substance with the olfactory receptors in the nostrils. This interaction is influenced by many factors such as the composition of the substance, its volatility or the number and type of olfactory receptors of each individual.
In the olfaction process, odorant substances are transported through the air, reach the olfactory epithelium where they are detected by the receptors of the sensory receptor neurons. The olfactory epithelium has between 20 and 30 million receptor cells which, when activated, transmit the signal to the cerebral cortex and, from there, to the limbic system and hippocampus where olfactory memory is established and memories are associated with certain odors.
It is estimated that humans have the ability to differentiate up to ten thousand different odors, but most of us will only perceive a fraction of them in our lifetime, so the description of an odor often varies from person to person. In addition, olfactory perception is also influenced by cultural, emotional or physiological aspects.
One of the best known odorant compounds are ionones, which are natural compounds found naturally in the scent of flowers where they serve as an attractant to pollinating insects. They are widely used in perfumery and as food flavorings.
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