Special senses / Olfaction / Odourants
Odourants
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olfaction detects chemical stimulants
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numerous attempts have been made define odour qualities --- essentially on a scale from pleasant to unpleasant--- but (until recently) development of a scale related to chemical structure was unsuccessful, and the inability to define the stimulus hindered the study of olfactory physiology
Linnaeus (1752) |
Haller (1763) |
Zwaardemaker (1885) |
Henning (1915) |
Amoor (1962) |
Aromatic |
Pleasant |
Aromatic |
Fruity |
Ethereal |
Ethereal |
Flowery |
Floral |
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Fragrant |
Fragrant |
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Ambrosial |
Ambrosial |
Pepperminty |
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Intermediate |
Empyreumatic |
Spicy |
Camphoraceous |
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Alliaceous |
Alliaceous |
Resinous |
Musky |
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Hircine |
Hircine |
Burnt |
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Foul |
Repulsive |
Pungent |
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Nauseating |
Unpleasant |
Foetid |
Putrid |
Putrid |
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Incremental changes in chemical structure produce detectably different odours.
Johnson and Leon (2007) -
our understanding of olfactory transduction was significantly advanced with the discovery of olfactory receptor genes - this discovery allowed the receptor code to be reverse engineered
- i.e., instead of definining the stimulus, then studying transduction (as was done in the auditory and visual systems), in the olfactory system, the major breakthrough was discovering the receptor structure, and then piecing together what stimulates each type of receptor
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there are approximately 330 olfactory receptor genes, which code for ~1000 receptors in the main olfactory epithelium and 100 in the vomeronasal organ
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reinivigorated field to take another look stimuli - a recent analysis of responses to 345 odourants was able to define at least 6 different dimensions that lead to different patterns of activity in neurons in the olfactory bulb