Sense+of+Smell+Project+MV

**Facts:**
- 80-90% of what we perceive as "taste" actually is due to the sense of smell, which accounts for how dull food tastes when we have a head cold or a stuffed-up nose. - Sense of smell depends on between 10 and 20 million olfactory cells located within olfactory epithelium high in the roof of the nasal cavity. - Olfactory cells are modified neurons. Each cells ends in a tuft of about five olfactory cilia, which bear receptor proteins for odor molecules. http://i61.photobucket.com/albums/h53/mocost/Gray772-1.png

- The olfactory epithelium in humans is located high in the nasal cavity. - Olfactory cells end in the cilia that bear receptor proteins for specific odor molecules. The cilia of each olfactory cell can bind to only one type of odor molecule (signified by color). If a rose causes olfactory cells to be stimulated by "blue" or "green" odor molecules, then neurons designated by blue and green in the olfactory bulb are activated. The primary olfactory area of the cerebral cortex interprets the pattern of stimulation as the scent of a rose.

**How the Brain Receives Odor Information:**
Each olfactory cell has only one out of several hundred different types of receptor proteins. Nerve fibers from like olfactory cells lead to the same neuron in the olfactory bulb, an extension of the brain. An odor contains many odor molecules, which activate a characteristic combination of receptor proteins. For example, a rose might stimulate olfactory cells, designated by blue and green, while a gardenia might stimulate a different combination. An odor's signature in the olfactory bulb is determined by which neurons are stimulated. When the neurons communicate this information via the olfactory tract to the olfactory areas of the cerebral cortex, we know we have smelled a rose or a gardenia. Have you ever noticed that a certain aroma vividly brings to mind a certain person or place? A whiff of a perfume may remind you of a specific person, or the smell of boxwood may remind you of your grandfather's farm. The olfactory bulbs have direct connections with the limbic system and its centers for emotion and memory. One investigator showed that when subjects smelled an orange while viewing a painting, they not only remembered the painting when asked about it later, but they also had many deep feelings about it. The number of olfactory cells declines with age, and the remaining ones become less sensitive. Therefore, older people tend to apply excessive amounts of perfume or aftershave before they can detect the smell. This can be dangerous if these individuals cannot smell smoke or a gas leak.