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Name: Francis
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The Word Scent is used in many contexts, perfume, a hunting animals ability and so it goes on. How would you describe as concisely as possible what scent is. My specific interest, as an example, an animal moves through some cover and leaves scent, what has it left exactly and why does it fade with time. Also how does the process of scent detection work?

Biologists generally refer to this as the olfactory sense. Since olfaction and gestation (taste) are entwined such things as "scent" are tricky. Scientists generally try to isolate the actual chemicals that these two senses are detecting. Regarding the olfactory sense here is some background:

A olfactory receptor can respond to a variety of chemically related molecules. Our ability to discriminate among thousands of odors most likely is a result of multiple chemicals in a certain source of an odor that activates a set of olfactory receptors.

Although the nervous system detectors for gustation and olfaction are separate, they often work together. We know this when we do not enjoy the "taste" of food when we have a cold and cannot smell the food. There are fun experiments you can do in classrooms with students holding their noses and tasting different flavored candies.

When the receptors in our olfactory bulbs (in our nasal area) or the taste buds in our tongues interact with various chemicals they send signals through nerve fibers to the brain. There is strong evidence that the brain combines these signals in some way that is not very well understood. One thing is certain, odors can be very powerfully seated into our long-term memory. We all experience this when a certain smell vividly brings back memories.

We have known for some time that taste buds get regenerated every few weeks. In the olfactory system the cells that detect the chemical(s) in an "odor" or "scent" have a much more direct connection to the brain. The olfactory cells also get regenerated, but over a few months, rather than a few weeks and what is surprising is that the neurons' connections to the brain also get regenerated unlike in the taste buds. So we wonder why would the olfactory nerve cells go through this rewiring to the brain? The best guide in these questions is for us to ask, what evolutionary advantage would this provide. Since we do not understand olfaction very well, this is a difficult question to answer. I suspect it has to do with the way olfaction is related to our survival (evolutionarily) and it being a sense that is deeply connected with primitive parts of our brains. Some interesting questions to explore with students along this line is...why, when one person vomits do others have a sympathetic response, why are odors perceived as so objectionable and others not? Are their odors that we are not consciously perceiving but nevertheless control our behavior...pheromones???


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