The document describes how our sense of smell works. It explains that odor molecules are sniffed into the nose and activate receptors in the olfactory epithelium, triggering neurons that send signals to the brain. Each neuron responds to just one smell molecule, allowing our brains to perceive complex odors. The document also discusses how dogs have a much more developed sense of smell than humans due to differences in their olfactory systems.

1. Sense of Smell
The nose contains the nerves that allow us to smell. Smell are powerful at
activating memories, triggering emotions, and alerting us to danger.
Let’s describe on how we smell things. Now the process starts as we sniff
molecules up into our nose. This mean for you to be able to smell something odorant
must be volatile (easily evaporated at normal temperatures) or in a gaseous state to get
sucked up and your nostrils, And yes that means when you smell poop there are actual
poo particles up in your nose
The harder and deeper you sniff the more molecules you vacuum and the more
you can smell it. Most of these molecules are filtered out on the way up your nasal cavity
as they get caught by your protective nose hairs but a few make it all the way to the back
of the nose and hit your olfactory epithelium. this is olfactory systems main organ a small
yellowish patch of tissue on the roof of the nasal cavity. The olfactory epithelium contains
millions of bowling pin shaped olfactory sensory neurons surrounded by insulating
columnar
Incidentally, a dog’s olfactory epithelium is way bigger than ours and contains way
more receptor neurons, which is why our fuzzy friend can smell things way beyond what
we could even imagine.
So these airbone pizza molecules many of which are just broken off parts of fats
and protines land on your olfactory epithelium and dissolve in the mucus that coats it
Once in the mucus they’re able to bind to receptors on your olfactory sensory
neurons which assuming they hit their necessary threshold, fire action potentials up their
long axons and through your ethmoid bone into do olfactory bulb in brain

2. But here’s the wonder of specialization for you: Each olfactory neuron has
receptors for just one kind of smell And any given odorant, are made up of hundreds of
different chemical that you could smell like
So, after each smell-specific neuron is triggered the signal travels down its axon
where it converges with other cells in a structure called of glomerulus. This takes its name
from the latin word glomus meaning “ball of yarn” which is what it looks like a tangle of
fibers that serves as a kind of transfer station, where the nose information turns in the
brain information. Inside the glomerulus the olfactory axons meet up with the dendrites of
another kind of nerve cell called a mitral cell which relays the signal to the brain. So for
each mitral cell there are any number of olfactory axons synapsing with it, each
representing and identifying single volatile chemical. As a result every combination of an
olfactory neuron and a mitral cell is like a single note and the smell coming off triggers
countless of these combinations forming a delicious musical chord of smells just imagine
a piano with thousands of he's able to produce millions of unique cord and then you get
an idea of how amazing our nose are
So once a mitral cell picks up its signal from an olfactory neuron, it sends it along
the olfactory tract to the olfactory cortex of the brain
Sense of Taste
Taste Buds- Most taste buds are located on the tongue, but a few are scattered along the
cheeks, soft palate, pharynx and epiglottis.
Most taste bud are packed deep down between your fungiform papillae those little
projection that make your tongue kinda rough
How does our sense of taste work?
A bitter pill, sour grapes or sweet nothings – descriptions of taste are very often associated with
strong emotions. They express in words states of intense pleasure as well as displeasure.
This strong link connecting taste with emotion and drive has to do with our evolution: Taste was
a sense that aided us in testing the food we were consuming. It was therefore a matter of survival.

3. A bitter or sour taste was an indication of poisonous inedible plants or of rotting protein-rich
food. The tastes sweet and salty, on the other hand, are often a sign of food rich in nutrients.
It starts at the tongue: From substance to taste
But what is taste actually? What happens in our body that enables us to perceive flavor? The
chemical substance responsible for the taste is freed in the mouth and comes into contact with a
nerve cell. It activates the cell by changing specific proteins in the wall of the sensory cell. This
change causes the sensory cell to transmit messenger substances, which in turn activate further
nerve cells. These nerve cells then pass information for a particular perception of flavor on to the
brain.
The numerous wart-like bumps on the mucous membrane of the tongue are where the substance
producing the taste is transformed into a nerve signal. These bumps, which are called taste
papillae, contain many sensory cells with a special structure: together with other cells they make
up a bud that looks a bit like an orange with its sections arranged around a center.
In the middle of the top side is a small indentation filled with fluid. The chemical substances
responsible for the taste are washed into this funnel-like hollow. This makes sure that the
substances are detected and analyzed by as many sensory cells as possible before being
swallowed.
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What are taste papillae?
The taste papillae are a good number of wart-like bumps under the mucous membrane of the
tongue. They increase the surface area of the tongue several times and make sure that individual
tastes can be perceived more intensely. This is also called the magnifying effect of the tongue.
The papillae contain several taste buds with sensory cells.
There are three types categorized by their shape:

4. fungiform papillae
Fungiform papillae are the most common: between 200 and 400 bumps are spread all over the
surface of the tongue. They are found mostly at the tip of the tongue and at the edges where they
make sure that these areas are especially sensitive to taste. Fungiform papillae not only detect
taste, they also contain sensory cells for touch and temperature. Each papilla contains 3 to 5 taste
buds.
circumvallate papillae
Circumvallate papillae are very large and found at the base of the tongue, where the throat
begins. Every person has only 7 to 12 circumvallate papillae, yet these papillae each contain
several thousand taste buds. Circumvallate papillae are round, raised, and visible to the naked
eye. They are arranged in the shape of a V at the back of the tongue. These papillae are called
circumvallate papillae, because they are surrounded by a trench containing many glands that
“rinse” the taste-producing substances into the sensory cells.
foliate papillae
Foliate papillae can also be seen with the naked eye on the rear edges of the tongue. There you
can see several folds that lie close together. Our tongue has about 20 foliate papillae, each of
which has several hundred taste buds.
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What are taste buds?
Taste buds are the true taste organ. They have numerous sensory cells that are in turn connected
to many different nerve fibers.
Each taste bud has between 10 and 50 sensory cells. These cells form a capsule that is shaped
like a flower bud or an orange. At the tip of this capsule there is a pore that works as a fluid-
filled funnel. This funnel contains thin, finger-shaped sensory cell extensions, which are called
taste hairs. Proteins on the surface bind chemicals to the cell for tasting.

5. The taste buds are located in the walls and grooves of the papillae. Adults have between 2,000
and 4,000 taste buds in total. The sensory cells in the taste buds are renewed once a week.
Most of the taste buds are on the tongue. But there are also cells that detect taste elsewhere inside
the oral cavity: in the back of the throat, epiglottis, the nasal cavity, and even in the upper part of
the esophagus. Infants and young children also have sensory cells on their hard palate, in the
middle of their tongue as well as in the mucous membranes of their lips and cheeks.
The final step in perceiving taste is transfer to the nervous system. This is done by several cranial
nerves. All information is carried along the cranial nerves to part of the lower section of the
brainstem (the medulla oblongata). At that point there is a split: Some fibers carry taste signals
together with signals from other sensory perceptions like pain, temperature or touch through
several exchange points to consciousness.
The other fibers pass over these exchange points of conscious perception and leads directly to the
parts of the brain that are connected with sensory perception and which are responsible for
securing our survival. It is here that taste signals are combined with different smell signals.
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A virtually limitless palette of flavors
About half of the sensory cells react to several of the five basic tastes. They only differ by having
varying levels of sensitivity to the different basic tastes. Each cell has a specific palette of tastes
with fixed rankings: this means that a particular cell might be most sensitive to sweet, followed
by sour, salty and bitter, while another has its own ranking.
The full experience of a flavor is produced only after all of the sensory cell profiles from the
different parts of the tongue are combined. The other half of the sensory cells and nerve fibers

6. are specialized to react to only one taste. It is the job of these cells to transmit information on the
intensity of the stimulus – how salty or sour something tastes.
Assuming 5 basic tastes and 10 levels of intensity, 100,000 different flavors are possible. Taken
together with the senses of touch, temperature and smell, there are an enormous number of
different possible flavors.
Often referred to as our “sixth sense,” balance relies on input from
several areas of the body to keep you from falling — the inner ear, the
eyes, the muscles and joints in your leg and spine.
Have you ever wondered why you are able to stand upright or walk across a
room without falling?
Well, your vestibular (balance) system has a lot to do with that.
This sensory system is different from all other senses in your body. Each of
your other senses has only one input: You see with your eyes, smell with your
nose, taste with your tongue, etc.
The vestibular system, however, has several sensory inputs: Balance organs
of your inner ear (five on each side), visual inputs and inputs from the muscles
and joints in your legs and spine. These inputs unite in the balance centers of
the brain to give you a sense of balance. This forms a “sixth sense” as it
sends information about head motion and orientation to the brain for
processing in order to send the right commands to your different organs for
performing daily life activities.

7. Your balance systeminaction.InfographicbyGaryfalliaPagonis.
In action, our vestibular system has three main functions: gaze stability, gait
stability, and spatial orientation. We checked in with Dr. Steven Rauch,
Director of the Vestibular Division at Mass Eye and Ear, to learn more about
these functions and why they are important.
Gaze Stability
More than meets the eye. Stare at a fixed point on the wall in front of you
while moving your head from side to side. Notice how your eyes rotate in
order to stay fixed on that point, rather than moving with your head? That
would be because of your vestibular system. As you turn your head, your

8. vestibular system helps rotate your eyes. This is called the vestibule-ocular
reflex.
Gait Stability
On your mark… Maintaining an upright stance on one or two feet requires
constant communication between the sensory signals from the feet, legs and
spine to the brain. These muscle signals are sent to the brain and then back
down to make adjustments in your body that will keep you upright and stable
in a variety of activities—like keeping you steady while running.
Spatial Orientation
Round and round we go! The vestibular system helps you perceive which
way you are spinning on a merry-go-round, which way you are tilting on a boat
and simply, which way is up. These perceptions contribute to your sense of
equilibrium (state of physical balance) and keep you safe from falling.
Next time you are walking around or enjoying a boat ride, think about how
your vestibular system is working to help you maintain your stability and sense
of balance!
If you experience dizziness or sense of imbalance, discuss this with
your doctor and consider seeing an ear, nose and throat specialist for
evaluation.