Smell

Tulips starting to smell, too offputting. But better than the smell of paint that still permeates my new studio. Question: do smells ad up, or subtract? Searching the ‘net for an answer, I came up with interesting blogs about smells and the city here and here. The beginning of an answer I found here, quote:

Buck, also a Howard Hughes Medical Institute investigator, and her team reported their findings in a recent issue of the journal Cell. These findings “explain several things that puzzled people for a long time,” Buck notes. “If you alter the structure of an odorant — even slightly, its smell can undergo profound change.” And a shift in concentration can turn a scent from pleasant to disgusting. Take octanol, for example. An ingredient of petroleum and natural gas, it exudes an orange- and rose-like bouquet. Change one atom in the molecule’s structure, and it becomes octanoic acid, which is characterized by a rancid, sweaty smell. When concentrated, indole, a substance found in both coal tar and perfumes, just plain stinks. When sufficiently diluted, indole gives off a fragrance like jasmine.

Odors waft up the nasal cavity to a patch of nerve cells above the eyes. From there, scent signals go to the olfactory bulb, higher brain areas involved in discrimination (frontal lobe), and primitive areas linked to emotions (limbic system). “When you alter the concentration or structure of an odorant, you also change its receptor code and, thereby, its smell,” Buck says.

Odorants are vaporized from gasoline, baking bread, or perfume, and waft up the nasal cavity, where they contact nerve cells. Each cell extends thin hairs, or cilia, and the odorant receptors sit on those hairs. When an odorant binds with receptors, the cell sends a signal to the brain, specifically to the olfactory bulb above the eyes. In the nose, cells that use the same receptor lie scattered over the wall of the nasal cavity. Their signals, however, go to only two spots in the olfactory bulb. Signals from different sensors are targeted to different spots and so form a sensory map that is the same in every mouse and, probably, every human. From this cerebral switching center, nerve fibers carry scent messages to both higher brain areas involved in conscious discrimination and perception of odors, and to more primitive areas that mediate emotions, such as fear, loathing, sex, and pleasure.

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