Process Paper

“How Your Sense of Smell Works”

“Olfaction”(also known as olfactics) which is the medical term defining your sense of smell. It is part of the chemical sensing system, or the chemo-receptors. Sensory cells in the nose, mouth and throat have a role in helping interpret smells and taste flavors. Microscopic molecules released by substances, such as food, stimulate these sensory cells. Once the cells detect the molecules they send messages to the brain, where the smell is identified.

How does the brain recognize, categorize and memorize the huge variety of odors? In 1991, Richard Axel and Linda Buck published a paper on how the brain interprets smell. Axel and Buck discovered that 3% of the human body’s gene total is coded for the olfactory receptor types. Every olfactory receptor cell has only one type of receptor. Each receptor type can detect a small number of related molecules and responds to some with greater intensity than others. Essentially, it was discovered that receptors cells are extremely specialized to particular odors.

The researchers also found that the olfactory receptor type sends its electrical impulses to a particular micro-region of the olfactory bulb. The micro-region, or glomerulus, that received the information then passes it on to the other parts of the brain. The brain then interprets the “odorant patterns” produced by activity in the different glomeruli as smell. There 2,000 glomeruli in the olfactory bulbвЂ"twice as many micro-regions as receptor cellsвЂ"allowing us to perceive a multitude of smells.

Olfactory, or smell nerve cells, are stimulated by odors such as the fragrance of a gardenia or the smell of bread baking. These nerve cells are found in small patches of tissue (the olfactory membranes) about the size of a postage stamp that are located in the pair of clefts just under the bridge of the nose high inside the nose. Most air breathed in normally flows through the nose but only a small part reaches the olfactory clefts, enough to get a response to an odor. When a person sniffs to detect a smell, air moved faster through the nose, increasing the flow to the olfactory clefts and carrying more odors to these sensory organs.

In humans, the organ of smell is situated in the mucous membrane of the upper portion of the nasal cavity near the septum. It is made up of the olfactory cells, which are actually nerve cells that function as receptors for the sense of smell. The free ends of the cells project outward from the epithelial tissue in the form of numerous hair-like processes.