Your
Sense of Smell: In Scientific Terms
- by KissMeGoodnight.com
The sense of smell is one of the most fascinating
of all of our sensual receptors. It is also one of the most
critical for all animal species. As humans, we can detect and
distinguish more than nine thousand odors. We use our
sense of smell for any number of different things, including enjoying
the aromas of our favorite foods and beverages as well as deciding
whom we want to associate with based on smell. We can use it
to detect danger as in a fire or a gas leak, and we can use
it for fun like in reading scratch and sniff books to our children.
Over the course of the past twenty years, science has made
extensive study of the human sense of smell. The science community
can now tell us both how our nose detects odor molecules and
how the brain is able to deal with that information once it
is detected.
Every odor your nose detects comes from molecules, tiny particles
emitted from the object. Almost everything emits a smell, but
some of them don’t reach as far as others. For example, bread,
onions, perfume, fruit, and similar things give off many light,
volatile molecules that are long range. They float through
the space around the object and eventually end up in your nose.
Other objects, like steel for instance, gives off molecules,
but they are not long range and do not float as easily. As
a result, we might say it has no smell.
Your
sense of smell kicks in when the molecules enter your nose. At the very top of the nasal passage, there is an area,
around the size of a postage stamp, which contains a large
patch of neurons. Actually, it contains millions of neurons,
called olfactory receptor neurons. The area is called the olfactory
epithelium. The interesting, and unique, thing about these
olfactory receptor neurons is that they are unprotected. This
means they can come into direct contact with the air you breathe
in. Their projects, a bit like hair, increase the surface area
they can reach. The projections are called cilia. As an odor
molecule comes up the nasal passage. The cilia will trap it.
This forces the olfactory receptor neuron that the cilia are
attached to, to send a message to your brain and cause you
to perceive a smell.
Not
everyone perceives the same smells, though. Recently,
scientists discovered that the ability to smell certain odor
molecules is genetic. Your individual genome encodes your olfactory
receptor neurons. Each of the receptors has a place where an
odor molecule can form a bond with it so your brain can perceive
the smell correctly. If the right molecule falls into the right
place, you get the smell. If, however, you are missing a genetic
sequence, or the correct genetic sequence has been damaged
in that area, your olfactory receptors are unable to accept
the molecule. As a result, your brain is unable to receive
the electrical impulse, and you never get the smell. It is
possible to regrow these olfactory neurons if they are damaged.
There
are four zones of olfactory receptor neurons within your
brain. These four zones can help to distinguish the quality
of the odor, the intensity of the odor, and the type of odor
you are detecting. Even babies in the womb have a sense of
smell. By nine weeks into gestation, the nasal cavity has separated
from the mouth. It is at this point that the olfactory receptor
neurons are formed. By the thirteenth week of gestation, the
connections between the baby’s brain and the olfactory receptor
neurons are formed. From that point onward, the baby can smell
throughout the gestation. Smelling does not require air; it
simply requires the odor molecules, which can be transmitted
through the amniotic fluid. In some scientific studies, a baby
can recognize its mother’s scent immediately after birth.
The sense of smell is often termed one of our chemical senses
because it requires that we process the chemicals around us
for use. Smell can alert us to danger, but it can also offer
us a sense of recognition. Ever have someone wander by you
wearing your mother’s perfume? You probably immediately recognized
it as such. The sense of smell, as complicated as it is, is
one of our most powerful. Click here for the largest selection (over 15,000) and best prices (up to 80% off) for perfumes and colognes. It's my KissMegoodnight recommendation.
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KissMeGoodnight.com
: 2006
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