Animal Scent Biology
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
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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Update: June 2012