Some people think that the sense of smell is not as important as other senses, such as sight or hearing. However, smells can be very powerful in the emotions or memories that they trigger for certain people. A sense of smell is also important in helping a person taste things.
About Smell
Smell occurs when substances that are easily vaporized release airborne molecules. This is also true for substances that easily dissolve in waterthe more easily something dissolves, the stronger its smell will be. In contrast, any nonvolatile substances, such as glass, do not give off smell molecules.
How Smell Travels
Smell travels very simply, by being carried on wafts of air into the sensory cells of the nose. (see Reference 1)
How Do We Smell?
When you take a breath, air is sucked into your nostrils over bony ridges inside of your nose. These ridges add more surface area to your sensory cells, and as air travels over millions of olfactory receptor neurons, odor molecules stimulate and inhibit these receptors. Different aromas set off various receptor signals that travel along the olfactory nerve to the olfactory bulb, which is located right beneath the front of your brain. It is these signals that tell the brain what something smells like.
How We Perceive Smell
When molecules affect receptors inside the nose, the combined effect allows the brain to identify the smell, much like how a yellow and red light combined is interpreted by the brain as the color orange. Overall, the brain has to analyze a mixture of odorants in order to recognize a smell.
Trivia
People can recognize about 10,000 different smells, and no two people perceive the same smell the same way. Nobel laureates Richard Axel of Howard Hughes Medical Institute and Linda Buck at the Fred Hutchinson Cancer Research Center found out during a study in 1991 that there are about 1,000 genes that encode the receptors inside the human nose. Their research also showed that each receptor is sensitive to only a small number of odors.
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