Chemicals dissolved in air chemically bind to upper-nose odor receptors {smell, sense}| {olfaction}. Smell qualities depend on molecule electrical and spatial-configuration properties, such as shape, acidity, and polarity. Smell is a synthetic sense, with some analysis. People can distinguish 20 to 30 primary odors and more than 10,000 different odors.
physical properties
Smellable molecules include many types of typically hydrophobic volatile substances with molecular weights between 30 to 350. Air-borne molecules vary in size, shape, chemical sites, and vibration states. Air-borne chemicals vary in concentration. Smellable chemicals chemically bind to upper-nasal-passage chemical receptors.
primary-odor receptors
Some people cannot smell camphorous, fishy, malty, minty, musky, spermous, sweaty, or urinous odors (primary odor). Camphorous molecules have multiple benzene rings. Fishy molecules are three-single-bond monoamines. Malty molecules are aldehydes. Minty molecules have a benzene ring and an oxygen-containing side group. Musky molecules have multiple rings. Spermous molecules are aromatic amines. Sweaty molecules are carboxylic acids. Urinous molecules are steroid ketones. Fruity molecules are organic alcohols.
types
Odors can be acidic, acrid or vinegary, alliaceous or garlicy, ambrosial or musky, aromatic, burnt or smoky, camphorous or resinous, ether-like, ethereal or peary, floral or flowery, foul or sulfurous, fragrant, fruity, goaty or hircine or caprylic, minty, nauseating, peppermint-like, pungent or spicy, putrid, spearmint-like, sweaty, and sweet.
Perhaps, the first smells were mating, food, or poison signs.
qualities
Smells can be sweet, acidic, or sweaty. For example, musk, ether, ester, lowery, fruity, and musky are dull, sweet, and smooth. Vinegar and acid are sharp, sour, and harsh.
Smells can be cool, like menthol, or hot, like heavy perfume. For example, menthol is cool, and perfume is hot.
Aromatic, camphorous, ether, minty, musky, and sweet are similar. Acidic and vinegary are similar. Acidic and fruity are similar. Goaty, nauseating, putrid, and sulphurous are similar. Smoky/burnt and spicy/pungent are similar. Camphor, resin, aromatic, musk, mint, pear, flower, fragrant, pungent, fruit, and sweets are similar. Putrid or nauseating, foul or sulfur, vinegar or acrid, smoke, garlic, and goat are similar. Vegetable smells are similar. Ethers are vegetable. Animal smells are similar. For example, caprylic acid and carboxylic acids are animal. Halogens are mineral
Acidic and sweet smells are opposites. Sweaty and sweet smells are opposites.
Smell always refers to object that makes smell, not to accidental or abstract property nor to concept about smell. In contrast, color always refers to object property.
Odors have same physical properties, and smell physiological processes are similar, so odor perceptions are similar, with same odors and odor relations, for people with undamaged smell systems. Smells relate in only one consistent and complete way. Smells do not have symmetric smell relations, so smells have unique relations. Smells cannot substitute or switch.
People can smell specific odors and not others. People can smell sweet as putrid and have other smell exchanges. People can always smell something.
mixing
Smells blend in concordances and discordances, like music harmonics. Pungent and sweet can mix. Pungent and sweaty can mix. Perhaps, smells can cancel other smells, not just mask them.
timing
Brain detects aldehyde smells first {top note, smell}. Brain detects floral smells second {middle note, smell}. Brain detects lingering smells, such as musk, civet, ambergris, vanilla, cedar, sandalwood, and vetiver, later {base note, smell}.
properties
Smell habituates quickly. Smell is in real time, with a half-second delay. Smell short-term memory is poor. Smell strength decreases with age. Fats absorb pungent food odors.
Butyrate and squalene odor patterns identify species members. In mammals, small pheromone amounts establish territories [Pantages and Dulac, 2000]. Humans have strong odors from hair-follicle apocrine glands. Perhaps, human odor warns predators away. Babies have small glands. Stress seems to cause odor. Menses smells like onions.
source location
Olfactory bulb preserves odor-receptor spatial relations. Smell cortex can detect smell location in space. Smell can detect several sources from one location. Smells from different sources can interfere.
diseases
Diabetes smells like sugar or acetone. Measles smells like feathers. Nephritis smells like ammonia. Plague smells like apples. Typhus smells like mice. Yellow fever smells like meat.
emotions
Smells can make people feel disgusted, intoxicated, sickened, delighted, revolted, excited, hypnotized, and pleasured. Smells can be surprising, because smells have many combinations.
evolution
Perhaps, the first smells were mating, food, or poison signs.
Butyrate and squalene odor patterns identify species members. Humans have strong odors from hair-follicle apocrine glands. Stress seems to cause odor. Perhaps, human odor warns predators away. (Babies have small glands.)
In mammals, small pheromone amounts establish territories [Pantages and Dulac, 2000].
development
In first few days, newborns can distinguish people by odor.
relations to other senses
Taste and retronasal-area smell can combine to make flavor. Taste has higher concentration than smell. Smell uses air as solvent, and taste uses water. Smell does not use molecule polarization, but taste does. Smell does not use molecule acidity, but taste does. Smells interfere with each other, but tastes are separate and independent. Taste does not use molecule vibrations, but perhaps smell uses vibrations. Taste and smell are both often silent. Taste and smell have early, middle, and late sensations. Smells and tastes have spatial source.
Smell is at body surface and so has touch. Touch can feel air near smell-receptor cells and react to noxious smells. Touch locates smell-receptor cells in upper nose. Trigeminal nerve carries signals from nose warmth-coolness, touch, and pain receptors.
Trigeminal nerve carries signals from nose warmth-coolness, touch, and pain receptors. Smell is at inner-nose surface and so has touch. Touch can feel air on inner nose and react to noxious odors. Touch locates olfactory receptors in upper nose.
Smell uses tactile three-dimensional space to locate smells in space.
Odor is painful at high concentrations.
Consciousness>Consciousness>Sense>Smell
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Date Modified: 2022.0224