Introduction: Neuroanatomy Video Lab – Brain Dissections

Introduction: Neuroanatomy Video Lab – Brain Dissections


>>Welcome to the University of
Utah, neuroanatomy laboratory. We’re going to go inside and do
some dissections of the brain and look at some of the
important structures that are useful for understanding neurological
principles and localization. [ Silence ] The purpose of neuroanatomy and
all of its tortuous tracts is to allow you to do
neurological localization. That is to say, decide
where in the brain of your patient the disease
process is occurring. That’s the total reason
for most of you to want to understand the
connectivity of the brain. Now let’s look at the
surface of the brain. We removed the coverings;
the leptomeninges (the pia and the arachnoid) and I want
to show you the different lobes of the brain as an introduction. In addition, on this brain,
you can see the brainstem. The brainstem extends from
this region where my probe is, a little bit difficult to
see, down all the way here to where the spinal
cord was attached. In addition, you can see
the cerebellum involved with coordinated motor
control as well as the surface of the cerebral cortex. This is the ventral
surface of the brain. And the most prominent feature
here is the temporal lobe, which I am outlining. Here is the temporal
lobe on the other side. And in front of it
is the undersurface of the frontal lobe. Cranial nerves are attached
such as the visual optic nerve and the sensory nerve from
the face or trigeminal nerve and blood vessels, such as
this large basilar artery, are running on the surface or you can even see the large
internal carotid artery. We will come back and look at
the nerves and the arteries and the other connections in
greater detail, but I just want to introduce you to the
region of the medulla, the pons, and the midbrain. And together, they
make up the brainstem. Let’s look at the lateral
surface now of the brain and look at the different lobes. You already saw the
inferior surface of the temporal lobe coming
back to here and we just kind of arbitrarily draw
a line and say that this is approximately
the end of the temporal lobe
posteriorly and the tip of the temporal lobe anteriorly. And then we look for a sulcus
on the surface of the brain. Sulci are these grooves
and the surface structures that are coiled are the gyri. So we have sulci
and we have gyri. The gyri have names but we’re
not going to learn most of them. However, this major sulcus, the
central sulcus, because it runs from the midline all the way down to the lateral
fissure separating it from the temporal lobe, this central sulcus separates
frontal lobe in front of it from parietal lobe behind it. And very interestingly,
the cortex involved in voluntary movement is in
front of the central sulcus. And the cortex involved with
primary somatic sensation from your body is the gyrus
behind the central sulcus. So, this is frontal lobe. This is parietal lobe. This is motor cortex in general, and this is sensory
cortex in general. So we’re just getting
our bearings. The frontal lobe is further
sort of divided and it’s hard to see the distinction, but this
band along here is the superior frontal gyrus, then we have
the middle frontal gyrus, and the inferior frontal gyrus. The motor cortex in front
of this precentral gyrus, as we call it because it’s in
front of the central sulcus, is an area involved,
in the left hemisphere, which we’re looking at, with
the production of speech. And you may have
heard of it before, it’s called Broca’s area. The rest of the frontal lobe
is either motor function, planning motor function,
or executive functions such as judgment and planning. Let’s look at the
parietal lobe now. The parietal lobe is separated
from the occipital lobe by an arbitrary line that
we draw between the parietal and the occipital regions,
these little notches here. So if I were to display here, I would say that approximately
this is the occipital lobe. The occipital lobe is
very important to humans because this lobe is involved with visual information
processing. It’s a wonderful
brain that we have, and we are very specialized as
humans for visual computation, orientation and analysis. So we have our four lobes,
occipital lobe involved with vision, parietal lobe
involved with sensation and integration of multiple
modes of sensory input, and the frontal lobe with motor
and higher order function. And this temporal lobe that is
down here is very much involved with auditory information,
which is coming in to this fissure here
that I’m pulling down. This is the lateral fissure. And auditory information,
sound, comes to both hemispheres and is processed here,
and this area behind it, the superior temporal gyrus,
this back part here is involved in the comprehension of
language (Wernicke’s area). So you’ve got two
language areas, an interpretative language area
and a production language area. And when we study the
consequences of cerebral stroke, we’ll see that some strokes
can knock out one area and you’ll have problems
producing intelligible speech, while other areas leave
you hearing perfectly fine but not understanding
what you’re hearing, and other lesions or damaging
strokes that involve all of this area can leave
you with a large deficit which we call a global aphasia. Aphasia is a language
disturbance. The temporal lobe in addition to having an auditory function
has an area underneath this gyrus here, which is
required in one hemispheres for forming new memories. It’s called the hippocampus
but is not visible here. So, temporal lobe, auditory and
new memories, occipital lobe, visual information, processing,
and recognition, parietal lobe, somatic sensation from the face
and the body, frontal lobe, motor execution voluntarily,
planning, and execution of appropriate judgment
and actions. The two hemispheres are
not identical, and later, we’ll talk about
special localizations between the hemispheres. But right now, I just
want to point to the fact, the two hemispheres are held
together by a large band of fibers called
the corpus callosum. What I have here is a coronal
section through the brain. What we’ve done is we’ve taken
our brain and we’ve sliced it like through this way, and so, this is called a coronal
or frontal section. And I’m going to rest it here so that you can see the
internal structure of the brain. We’ll deal with this in
more detail, but right now, you can see that those gyri
that we were looking at, and the sulci, the
dips in between, can be easily distinguished. And the gyri are covered with
a nice layer, beige in color, and that is your gray matter, as
we say, of the cerebral cortex. Maybe we should have
called it beige matter. And beneath it is
a lighter area, which we call the white matter. In general, gray matter consists
of cell bodies, both neurons and glia, and white
matter is axons. Axons are the processes
of neurons either coming to the cerebral cortex or
leaving the cerebral cortex and descending to
lower brain structures. An example of white
matter here is this band of fibers called
the corpus callosum. It was that band that held
the two hemispheres together when we were looking
down through that interhemispheric fissure,
the base of that was this band of white matter connecting
similar areas or homotopic areas of one hemisphere with the
other and this is a way that the right the left
hemispheres can communicate. In addition, they can
communicate through structures like this deep area,
you noticed it’s beige, so it’s mainly cell bodies. A deep structure
called the thalamus. And here, we can see
the temporal lobe that we were looking
at on the surface. Notice here, if I prop this up
and pull it down a little bit, you can see that large
lateral fissure that we saw on the lateral surface, that means that this
is the temporal lobe. We can even see a
blood vessel in there. This bit of cortex buried
underneath the hemispheric temporal and parietal
lobes is the insula. We’re not going to deal with
that but it does have a name. It’s where the cortex got buried as it became more
and more convoluted. This is parietal or it
could be motor cortex. I can’t tell for the isolated
section exactly if we’re in the frontal lobe
or the parietal lobe. It doesn’t really matter. And remember, I told you
that one of the functions of the temporal lobe in addition to the auditory region was
an area involved in memory. That area is called the
hippocampus and it’s curled up here right in this medial
part of the temporal lobe. The other major structure
you see in a cross section like this, or coronal section,
are these holes in the brain, one here, one here, one here, a
little bitty one here, and here. These formed part of
the ventricle system, which we will explore
further, but right now, just know that they are filled
with cerebral spinal fluid. And the leptomeninges or
the pia and the arachnoid on the surface, if we
can zoom in a little bit, we can see them delicately
covering the surface of the brain. The main thing I want you to see
on this brain is the brainstem. So, this is the cerebellum that
we saw before up to the side and the brainstem
recall was in the middle. Here, we have the
brainstem on a midsagittal. This is cut in the middle. So this is a midsagittal
section. Here’s a bit of the medulla. Here is the pons with the
big basilar artery creeping up over it and here is the
midbrain often hard to see. And finally, then we have deep
structures such as the thalamus and we can see many
of the vessels like the anterior cerebral
artery here as well as spaces such as the ventricular system which we’ll look
at in more detail. [ Silence ]

local_offerevent_note September 25, 2019

account_box Matthew Anderson


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