I like to say little bit more about what happens this information is passed from
the nucleus of the solitary tract through the thalamus.
Then from thalamus up to the cerebral cortex.
So with information is processed in our taste regions of the insular.
it's integrated with visceral sensory signals that are also processed in this
insular cortex. And that infromation then is passed onto
what we might consdier to be higher-order associational areas.
Especially in the orbital and medial parts of the prefrontal cortex.
And I would highlight one very interesting region of the orbital corext
of the brain, so here's the orbital surface.
It's that part of the brain that overlies the orbits of the eyes.
here again is our olfactory bulb and our lateral factory tract just for a little
bit of reference. I'd like to draw your attention to this
posterior part of the orbital cortex. This we think very well maybe the first
place in the cerebral cortex where flavors are represented.
This is a site anatomically that's receiving input from our Gustatory
pathway, as illustrated in the figure before us.
And if you'll recall our discussions about the olfactory pathways.
It's also a region that receives input from our primary olfactory cortex, such
as our piriform cortex. This is also an area, that is going to be
integrating signals derived from our trigeminal chemosensory pathways.
As well as, other higher order information from the somatic sensations
associated with feeding. So when we put all that together, what we
have is flavor, and a sense of the pleasure derived from that food.
be it of positive or, or negative, valence.
So we talk about the hedonic value of food, as being extremely important, in
reinforcing feeding behaviors. And this perspective on the value of food
seems to be represented in this part of the brain.
This posterior part of the orbital cortex.
Well information from, the cerebral cortex is also passed on, into structures
like the amygdala. As well as the hypothalamus, and so, we
can, appreciate from this anatomy, I think.
How information about the foods we ingest, can be distributed to a broad
cordical network. That's involved in representing the
signals derived from inside of our bodies and integrating that with our conscious
evaluations. And judgments about the significance of
these stimuli. Well we'll talk much more about these
topics when we get into the final unit of the course, when we talk about cognition.
The associational cortex in some of the truly fascinating, issues and modern
neuroscience, that revolve around our sense of judgement.
Our sense, of value, our sense of self. And how much of this is derived.
Not just from what we see and what we hear and what we touch in the world
that's beyond our fingertips. But also the world within these
sensations, including the chemical sensory signals.
And our visceral sensory signals that become integrated into our conscious
sense itself. So, I hope you'll enjoy that discussion.
Stay tuned for that. Okay, now, I think we're ready to turn
our attention to the problem of sensory transduction in the Gusatory system.
So, sensory transduction again, refers to the challenge of converting mechanical
energy, electromagnetic energy, or molecular energy into electrical signals
within a nerve cell. So we've seen how that happens in each of
the sensory systems. And let's consider now how it occurs in
the Gustatory system. So I'll just remind you that the
tastants, that is the actual molecules that will activate this system, obviously
are ingested. taken into the oropharynx where they can
interact with specializations of the epithelium.
We actually find these taste buds and specializations that we call papillae.
So, at the back of the tongue, we have a row of circumvallate papillae.
at the sides of the posterior tongue, we have.
They set a foliate papillae . And then in the interior part of the
tongue, we have what's called Fungiform Papillae.
And these names are just anatomical terms that describe a bit if the far,
morphology of these papillae. So don't, don't really be concerned with
the precise, configuration of this tissue that forms these papillae.
Unless this is of particular interest to you.
But otherwise I just want you to know that there are those papillae that are
distributed in different ways across the surfaces of the tongue.
And then the posterior part of the oral[UNKNOWN].
Now these posterior regions in the esophagus and in the soft palate are
going to be intervated probably by branches of the vegus nerve, nerve 10.
Here on the tongue, the posterior third of the tongue is going to be intervated
by branches of nerve 9, the glossopharyngeal nerve.
And the anterior two thirds of some of the tongue including these fungiform
papillae. These are going to be supplied By
branches of cranial nerve 7. Okay so this accounts for how nerves 7, 9
and 10 provide Gustatory signals into that nucleus of the solitary tract to the
brain stem. Well now let's look at the anatomy, the
microanatomy of one of these papillae. So, so what we see is that, is that
there's a bit of a trench so we can imagine that water soluble tastants, work
their way into these trenches. Where they can interact with these taste
buds, these specializations that we find in the lateral flanks of these trenches.
And it's within those specializations that we find our taste cells.
So here's a closer look at a taste bud. So, this is the, the tissue that we find
in the tongue. These taste buds include our sensory
receptor cells, our taste cells. And they also include a variety of basal
cells and supporting cells. Now the taste cells are the ones that, of
course, I would draw your attention to primarily.
these are sensory neurons that have an apical surface that comes together into
something that we call a taste pore. So it's specifically through this taste
pore that ingested molecules would interact with the ethical surface of our
taste cells. And its at that ethical surface, that
interact with the taste and molecules. Leading to the depolarization of those
taste cells. The release of neuro transmitter, and and
a synapse between the base of the taste cell.
And the axons of those three cranial nerves, nerves 7, 9 and 10.
Okay so, now let's focus in on this apical surface of taste cell.
And understand how sensory transduction happens.