Now we have two chemical sense. The sense of smell and the sense of
taste. The sense of smell is caused by hair
receptors that're located at the top of the noise, really in the olfactory bulb,
which a part of the brain that is sticking out right on the top part of the
nose. These hair cells hanging down and these
different kinds of hair cells can detect different chemical molecules producing
different odorants, thus different kinds of smell.
We estimate there are 5 million receptors on the olfactory bulb and there are
probably as many as 1000 different kinds of receptors that detect different kinds
of molecules. That have different odorants.
So we have a very complex ability to detect the chemicals in the air that
produce different kinds of smells. We also have taste.
Like smell, chemical receptors, in this case the chemical receptors are located
on the tongue, and they're located on taste buds, which by the way, last a very
short time. So the tongue is constantly replacing
taste receptors. Taste buds, the receptors are located on
the, on the taste buds themselves. And, and as we grow older the ability to
reproduce new taste buds declines. And thus we our sense of taste actually
declines with aging. because if you must constantly be able to
reproduce those taste buds to keep the same level.
There are different kinds of receptors located on the taste buds.
Receptors that detect salty, they detect sweet, bitter, sour, spicy and umami,
which is actually a savory kind of taste. And a combination of these.
You know, we can eat foods that we have the taste of both sweet and sour.
Spicy and bitter because as they reach different parts of the tongue.
You can have different sensations with the same foods.
Proprioception is important for us since the balance.
And there's two kinds of proprioceptions. One is information that comes from a
different parts of our body. From my finger from my foot.
That go up to the cortex around the central fissure where we last time showed
you the humunculus, so it goes to different places depend on what part of
the body is providing that information. That is called Kinesthesis, which is sort
of telling us what different parts of the body are doing in relation to each other.
Then there's another proprioceptive sense that's located in the inner ear along
with the Cochlea and that's the Vestibular senses.
The Semicircular canals and the Otolith sacks.
Here's a picture of the inner ear and you can see the Cochlea where we detect
sounds and then we have the Semicircular canals each one a different axis.
That tells us where we're moving and what direction we're moving.
And then these little parts here called the[UNKNOWN] sacs.
Which are actually container like substances with hair cells located all
around it. And it has something like little stones
in there, and depending on where your head is in relation to gravity, those
stones can fall down and stimulate the. The stimulate the hair cells.
Located around the container. So if I move my head from here to here.
Then the little stones are going to move down and stimulate different hair cells.
Constantly telling me where my head is located.
Now, like I said these are important for balance.
And if you over stimulate them, the semicircular canals in the[UNKNOWN] those
little stones are moving all around like riding a roller coaster.
Sometimes that can create a reaction which can be nausea, certainly dizziness.
inability to really figure out where we are in terms of balance.
So proprioceptive cues of a stimulus instance tell us where we are in relation
to gravity and whether we're moving. And where, what direction we're moving.
Sense of touch, I mentioned there are for kinds; there're receptors that receive
pressure, receptors that receive information about how hot something is,
cold and then pain. interesting that they also combinations,
like for example if I take two small rods, one filled with cold water and one
filled with warm water. And that the fluids are taveling through
those rods and I hold it in my fist, I will revieve hot, which is a combination
of those two receptors being fired. It's also if I move my hand across a part
of the body, stimulating different pressure receptors, that will lead to a
sensation of tickling. combination of different receptors
produce different sensations. Pain is an interesting one, because pain
the, the, goes up from the body when it's damaged up to the up to the brain, and
they cause really small fibers to go into the spinal cord and go directly to the
brain. There's also some large fibers that are
part of the pain perception, that when they're stimulated they actually inhibit
the small fibers. So we can do things like rubbing a wound.
The pain sort of is abated a bit and that's because the large fibers are
inhibiting the small fibers sense of pain.
The pain is very complex though because pain is, is perceived by the brain
depending upon things you've learned. Some people are very highly sensitive to
pain, some less so sensitive to pain. Also, pain can be abated by the large
fibers. Given the fact that like, if you're in a,
playing in a football game and you hurt something, you might not really feel that
pain because you're really working to, to do the task at hand until the game is
over, then the pain hits. So, we've dealt with the senses.
How information gets into the brain, and how the brain interprets that
information, and allows us to do things in the environment.
Thank you.