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Smell

The scientific term for smell is olfaction, and the system by which we smell is known as the olfactory system.

We detect smells by breathing or sniffing air that carries odors. Odors come from molecules of gas that have been released into the air from many different substances. These molecules stimulate receptor cells deep inside the nose. The cells, which are part of the olfactory nerves, are on layers of mucus-covered tissue. This tissue covers nasal bones called conchae. The receptor cells send the impulses created by the odor along the olfactory nerves.

nasal passages

The olfactory nerves then carry the impulses to a part of the brain called the olfactory lobe or olfactory bulb. The size of an animal's olfactory bulb is an indication of how important the sense of smell is to that animal. In dogs and some other vertebrates, the olfactory bulb is large, but in human beings it is small. From the olfactory lobe, the nerve impulses travel to the forebrain, the front part of the cerebrum of the brain, where the nerve impulses are translated into information about the odor.

olfactory bulb

Different smells can be distinguished by humans because molecules of certain odors become more quickly and more strongly attached to the mucus at a particular place on the conchae than do other molecules. Therefore, molecules of certain kinds of odors will always stimulate the same receptor cells on the conchae, meaning that an odor is distinguished by how fast and where its molecules become attached to the receptor cells.


The World Book Encyclopedia Chicago: World Book-Childcraft International, 1979

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This page was last updated on 09/24/2015.

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