Anatomy of the Brain

[SOUND EFFECT]

SPEAKER: All right, ninja nerds.

So we've already covered
the brain in another video.

Our intention in
this video is just

to be able to give
you guys another view

of the brain and some of
the internal structures.

So let's go ahead and
dive right into this.

So first off, if you
remember from before,

we had this central
sulcus here on the side.

And it's just this
little groove right here,

running right there.

This guy right there is actually
called the central sulcus.

So again, the central
sulcus is this little groove

right here running all
the way up right there.

And what's the purpose of it?

The central sulcus
separates the frontal lobe

from the parietal lobe.

So if I come up
the central sulcus

one more time, if I go right
in front of this sulcus

to this gyrus right
there-- because remember,

sulcus is this little divot.

And then a gyrus is this big,
fat, lumpy thing right there,

right?

This gyrus in front
of the central sulcus

is called the precentral gyrus.

It's also where the
primary motor cortex is.

And if I follow the central
sulcus because back up again

and I go to this fat gyrus
that's right behind it,

that guy right there is
called the postcentral gyrus.

And that's where the primary
somatosensory cortex is.

All right?

And then if I were
to go in front

of the primary motor here, which
is where the precentral gyrus

is, I'd hit the premotor.

And then you come
in front of that,

and you hit what's called
the prefrontal cortex and so

on and so forth.

There's even called the
eyelids, stuff like that.

But again, basic
important thing right here

is central sulcus, precentral
gyrus, postcentral gyrus.

The precentral gyrus
is functionally

called the primary motor cortex.

The postcentral
gyrus is functionally

called the primary
somatosensory cortex.

OK?

Then if I were to continue
to work my way back

to see where else does
the parietal lobe--

where does that terminate,
and where does it

go to another lobe?

So if I come over
here, I'm going

to take this brain and kind
of, like, open it up here.

Turn it around.

So if we look here, you'll see
another sulcus right there.

That sulcus right
there is actually

called the parietal
occipital sulcus.

And the parietal
occipital sulcus

is what separates the parietal
lobe from the occipital lobe.

So back here is
the occipital lobe.

I'll give you guys another
view here in a second.

Just let me repeat that
one more time again.

This is the parietal
occipital sulcus.

And the parietal
occipital sulcus

is what separates the
parietal lobe, which

begins right after
the central sulcus,

all the way up to this sulcus.

And it separates the
parietal lobe, again,

from the occipital lobe.

All right, guys, so
if we look back here,

we have the occipital
lobe back there.

Again, and what separates
the occipital lobe

from the parietal lobe is the
parietal occipital sulcus.

Again, this is the
occipital lobe.

In the occipital lobe,
there is a specific cortex

that's actually called
the primary visual cortex.

And so that's where, you
know, the actual signal

transduction that comes from our
retina that portrays basically

light, we can actually
have the perception

of that light in this area to be
able to perceive what we see--

you know, certain types of
objects and shapes and colors

and so on and so forth.

So again, primary
visual cortex is located

within the occipital lobe.

And then if I turn
this to the right side,

our lateral side over here,
we can see another sulcus.

And this sulcus is right here.

Actually, let me move
rubber band, guys,

so we can see a little better.

If I move that rubber band
right there and I move my finger

right-- or this
little pointer here--

right through this area,
right through that sulcus,

that sulcus right there is
called the lateral sulcus.

Now, the lateral
sulcus is the sulcus

that separates the
temporal lobe, again,

from the parietal lobe
and even a little bit

from the frontal lobe.

But this lateral sulcus
runs right down here,

and it separates
the temporal lobe

from the parietal lobe
and even a little bit

from the frontal lobe.

So again, what is this
lobe right here then?

I already said, this
is the temporal lobe.

And the temporal lobe has
a specific cortex in it,

which is called the
primary auditory cortex.

And the primary
auditory cortex is

going to be where we
take specifically sound

and hearing from the
cochlea in our inner ear

and we bring it to this area
to be able to perceive and put

together different
types of memories

to understand what
we're hearing,

and we're able to perceive
that hearing, right?

All right, so that's where the
primary auditory cortex is.

Again, that's the temporal lobe.

There is another
lobe we can't see.

And it's going to be deep
to the temporal lobe,

and that's called the insula
All right, so let's go ahead

and show you two
more other areas that

are kind of important here.

And what I'm going
to do is it's only

on the left side of
the frontal lobe.

It's called the Broca's area.

So the Broca's
area is just going

to be this little area
over here on the left side

of the frontal lobe.

Again, it controls the
muscles of speech production,

so being able to change
the shape of our mouth

and other types of muscles
that are basically assisting

with pronunciation and
production of consonants

and so on and so forth.

But again, just controls the
muscles of speech production.

There's another area back here.

It's kind of an overlapping
area right around here.

That's called the
word Wernicke's area.

Basically he just helps us to
be able to understand what we're

hearing and put
those words together

in a appropriate manner
that when we speak it,

it makes sense.

OK?

So he does help with being
able to play a role also

in speech production but
also understanding speech.

All right, so that's
the Wernicke's area.

Now what I'm going to
do is we're actually

going to kind of take
this guy here and turn it

forward here so I can show
you another structure.

This whole thing up
here is the cerebrum.

And the cerebrum--
and it's actually

derived from what's called
the telencephalon, OK?

That's its scientific name.

But what I'm going
to do is I'm going

to kind of separate these two
cerebral hemispheres right

there.

And what happens is
there's a fissure that

runs right between these two--

right between these two.

And that's called the
longitudinal fissure.

Called the longitudinal fissure.

Why I mentioned that
is there's what's

called dural sinuses
that are veins

that run through this area,
and we have to protect them.

So there's these things called
dural septum, which are just

little septal partitions
of dural matter

that dip down into this
longitudinal fissure

and protect the dural sinuses.

And that dural septa that comes
in here in the longitudinal

fissure is called the
falx, F-A-L-X, cerebri.

So falx cerebri.

And again, it's right here
in the longitudinal fissure.

All right, now I'm going to go
ahead and turn this guy around

so we can tell you
guys about another one.

So I'm going to
come back here, back

where the occipital lobe was.

And if you remember, this was
the occipital lobe, right?

Well, how do we know-- we know
where the parietal lobe is.

You remember, it starts
at the central sulcus,

and then it ends at the
parietal occipital sulcus.

And that's where the
occipital lobe begins,

at the parietal
occipital sulcus.

Where does it end?

It ends right back
here where there's

this little space in here right
between the occipital lobe

and the cerebellum right there.

So in between here is what's
called the transverse fissure.

And the transverse
fissure is important

because there's another
dural septa that

actually dips in that area.

And that right there is called
the tentorium cerebelli.

Cerebelli, OK?

Tentorium cerebelli.

And it's just a dural
matter partition or septa

that dips in that area.

OK?

Now what we're
going to do is we're

going to go ahead deeper into
the structures of the cerebrum

and take a look at that, OK?

All right, guys, so now
what I'm going to do

is I'm going to show
some other structures

underneath the cerebrum.

So deep in the cerebrum--

I just want to show you guys.

If you see all this white right
here, this is all white matter.

And what white matter is, is
it's just myelinated axons.

So it's myelinated axons.

And myelinated
axons just means it

has this thing
called myelin, which

is made up of fat and proteins.

It helps with basically
nerve conduction,

the speed of nerve conduction.

But anyway, myelinated
axons right here

is going to be the white matter.

All this pink stuff around the
edges or the outsides of it,

this is all part of what's
called our cerebral cortex.

And that's made of gray matter.

And gray matter is actually
unmyelinated cell body.

So there's no myelin
around the cell bodies.

OK?

So unmyelinated cell bodies
is our gray matter, which

makes up the cerebral cortex.

You can think of that like
as the thinking tissue.

So that's the part where they're
the biomechanical centers,

and they basically--

they're the ones that
control a lot of the thinking

or conscious thought.

This white matter, you
could think of that

as like transmission tissue.

It's basically responsible for
being able to transmit impulses

to and from certain areas.

OK?

So again, that shows
you the cerebral cortex

and, again, shows you the
white matter right there.

Now what we're
going to do is we're

going to take a look at
some other structures, which

is in the diencephalon
and the ventricles.

All right, guys, I have the left
cerebral hemisphere right now.

What I'm going to
do is I'm going

to take this top piece off
so we can take a deeper look

at some structures inside here.

All right, so if we
take a look in here,

right now we're kind of
in the lateral ventricle.

And ventricles are
just basically cavities

within the actual brain and
also within the brain stem.

And it contains what's
called cerebral spinal fluid.

And we'll talk about that more
in the neurophysiology stuff.

But if you look
right here, sitting

in the bottom of the
lateral ventricle down here,

this is actually-- if you
remember from the other video,

it's called the hippocampus.

And the hippocampus
is a limbic nuclei.

So it plays a role with
memory and emotions

and so on and so forth.

So it does play a very,
very important role

within, basically, memory.

If you look here, that's 190.

And if I come up here and
I follow these white fibers

like 186--

if I follow it all
the way from here,

all the way back, and then
I come back up this way--

so again, all the way up
here, following this guy,

and all the way back this way.

These fibers are very important.

They're called
association fibers.

And association
fibers are what allow

for the movement of
impulses to go from front,

from in front of the cerebrum
to the back of the cerebrum

or vice versa.

OK?

So again, these are
association fibers,

and this is the hippocampus.

And then this whole
cavity right here--

so like, for example,
this is the inferior horn.

This is the posterior horn.

And then we'll see the
anterior horn in a second.

That's all the
lateral ventricle.

OK?

And again, you can
see the white matter.

And then you can see the
gray matter out there.

So the last structure here
is going to be number 206,

and this is actually called
the internal capsule.

And the internal capsule
is actually specific fiber.

It's called a projection fiber.

And projection fibers
are important for being

able to bring sensory
information up

to the cerebral cortex, OK?

So they bring information
up, all right?

But they do-- they can allow
for information to go down also.

So they just basically offer
movement to go up and down.

So association is back and
forth, so back and front,

back and front.

And projection is up
and down, up and down.

And we'll look at another
one in a second called

the commissural fibers.

All right?

Now we're going to go ahead
and turn it around and look

at some other structures, guys.

All right, so I just
turned it around, guys.

So again, we're looking here
at kind of like the other view.

I was on the back side.

Now we're looking over
here on the front side.

So if you look right here,
there's a nuclei right here.

It's a basal nuclei.

And basal nuclei just
are important for being

able to dampen or smooth
out certain motor movements.

He's one of them.

He's called the caudate nucleus.

So that's the caudate
nucleus right there.

But this whole-- remember I told
you there was another anterior

horn of that lateral ventricle.

So there's a little cavity here.

And this whole cavity right
here is the lateral ventricle.

And if you look right here,
this structure right there

is actually called the-- it's
a choroid plexus, because there

is a choroid plexus,
which is basically

made up of ependymal
cells and pia mater.

And you're also going to have
your capillaries in there,

and it's what helps to be able
to make the cerebrospinal fluid

and circulate it.

So again, this is going to
be the lateral ventricle,

this cavity here.

Imagine it, like, bathing
this nucleus here.

Imagine it bathing
this caudate nucleus.

And imagine this
whole cavity filled

with cerebrospinal
fluid, and that's

made by this thing called
the choroid plexus.

And then you can see
this fiber right there.

There's another
white matter fiber,

and this is actually
called the fornix.

And the fornix is a white
fiber that actually-- it's

a tract, which is
a bundle of axons

in the central
nervous system that

connects multiple
limbic nuclei together.

So again, this
structure right here,

all the way from here,
all the way from here,

this is called the fornix.

And the fornix is
basically what helps

to be able to connect multiple
limbic nuclei together.

So again, last time,
lateral ventricle,

caudate nucleus, choroid plexus
of the lateral ventricle,

and the fornix.

All right, so now we're
going to go ahead and look

at some of these other
structures in the diencephalon.

All right, guys,
so this is right

here is the corpus callosum.

And the corpus callosum
number 145 here,

this is actually going
to be made up of what's

called commissural fibers.

And commissural fibers
are just, again,

myelinated axons that allow
for transmission of impulses

from left cerebral
hemisphere to right

or from right
cerebral hemisphere

to left cerebral hemisphere.

So it's very important
for that connection.

It's also an area
that's commonly

damaged during concussions.

And it's actually
been found that women

have more commissural
fibers than men do,

which allows for them to be able
to have a little bit better--

be better at multitasking
and stuff like that.

And it also plays a role in
epilepsy and stuff like that,

but we're not going
to get into that.

So again, corpus callosum there.

If you look here,
there's a membrane 146.

So this thin membrane here is
called the septum pellucidum.

And underneath the
septum pellucidum

is that lateral ventricle that
I was showing you guys before.

So underneath this
septum pellucidum

is the lateral ventricle.

OK?

So it's just a thin membrane
that separates the two

lateral ventricles.

Because, again, we have
a lateral ventricle

in one cerebral hemisphere.

Let's say the right one.

And we'll also have
a lateral ventricle

in the left cerebral hemisphere.

And the structure separating
them, this membrane,

is the septum pellucidum.

If you guys look at the
ventricle model we have,

you'll also see a better
way of looking at that also.

All right, let's
come back here again.

148 here, this is the fornix.

And again, that was
that fiber tract

that connects a lot of the
limbic nuclei together.

If I imagine I draw
a whole circle--

say I do a whole circle
all the way around here

or you imagine like an egg.

An egg is kind of like
oval-shaped, right?

So this whole thing right
here is the thalamus.

So this whole egg structure here
with a whole bunch of nuclei

is the thalamus.

And the thalamus is
actually the relay station

for a lot of sensory information
going up into the cerebrum,

because he has tons of nuclei
that regulate that activity.

Then if you look there, that
little brown structure right

there, that's called
the intermediate mass.

And it basically is like
an interthalamic adhesion

between the two
thalami, because you

have a thalamus in your
right cerebral hemisphere,

and you have a thalamus in
your left cerebral hemisphere.

So you have two of them.

If you actually imagine here--

imagine this being an
eye, like a bird's eye.

OK?

So if you can imagine it, you
can imagine the bird's eye,

which is kind of like
the white of the eye

is like the thalamus.

And then the pupil
right there is

where the intermediate mass is.

And if you imagine the
bird's beak right there,

this right there,
that bird's beak

is actually the hypothalamus.

So they can kind of say look
at the bird's eye and a bird's

beak.

And again, the
bird's eye is made up

of the thalamus and
intermediate mass.

And the bird's beak
is the hypothalamus.

If you look back
here, you have what's

called the pineal gland, which
is a part of the epithalamus.

Then you're also going
to notice this little--

the hypothalamus has
this little stalk

here on this side that connects
to the pituitary gland that

would sit right underneath
the optic chiasma.

Actually, this is-- if you
look at 170 there, that's--

where the optic nerves
cross, there's actually

called the optic chiasma.

So for example, this
is the right cerebrum,

so this would be the
right optic nerve here.

And it's getting ready--
some of its fibers

will cross over
to the left side.

OK?

So that's kind of like
the optic chiasma there.

And then this part right
there is the infundibulum.

But if you look right
there, that little,

like, ball there,
that right there is

called the mammillary bodies.

And the mammillary
bodies are also

important because they play
a role within certain types

of olfactory pathways.

So they play a role in smell.

That's the mammillary bodies,
and they're limbic nuclei.

So they play a role in
recollective memory,

stuff like that.

OK, if you come over
here, we're going

to see some other structures.

Now we're getting ready to
start moving into the brainstem.

So as we get ready
to move over here,

let's actually
hit our brainstem.

So if you look right here,
all this part right here,

this is all called the midbrain.

And they also call
it the mesencephalon.

So it was derived
from mesencephalon.

All this right here is our pons.

This is all our pons.

And the pons-- and this
right here is the cerebellum.

They were actually
derived from what's

called the metencephalon.

And then if we look here,
all the way over here,

this is the medulla oblongata.

And the medulla oblongata
was derived from what's

called the myelencephalon.

So again, I'll hit
it one more time.

Mesencephalon.

And then you got your
metencephalon, which is made up

of pons, and the cerebellum.

And then you have
your myelencephalon,

which is the medulla oblongata.

All right?

OK.

Another thing here is-- oh, I
also mentioned it a little bit

before.

I had mentioned that
all this area right here

is the diencephalon.

The diencephalon
is mainly made up

of three things, which we
said thalamus, hypothalamus,

and then technically
the epithalamus, which

consists of the pineal gland.

There's this little
cavity right here

that also contains
cerebrospinal fluid,

and this is called
the third ventricle.

So the third ventricle
would be a cavity right

in this vicinity right here.

So it actually gets drained
from the lateral ventricle.

So here's our third ventricle.

The third ventricle
actually drains

some of that actual fluid
from the lateral ventricle.

Then there's another little tube
right here running right here

through the midbrain.

So see that little
tube right there?

That's actually called
the cerebral aqueduct.

So the cerebral aqueduct
drains the third ventricle,

and the third ventricle
drains the lateral ventricle

via what's called the
interventricular foramen.

So again, third ventricle here
and then cerebral aqueduct

here.

Then the cerebral
aqueduct moves into what's

called the fourth ventricle.

And then from the
fourth ventricle,

the cerebrospinal
fluid can go two ways.

It can go down through
the central canal.

It will eventually go
through the central canal

of the spinal cord
or it can go out

through these two little holes
called the foramen Luschka

and the foramen Magendie.

Or you can say foramen Magendie
is the median apertures,

and the foramen Luschka
is the lateral apertures.

OK?

So that's that part there.

OK.

Now, if we look here in
the back of the midbrain,

we see these two little,
like, balls there.

All right?

This top one right there is
called the superior colliculi.

And basically what he helps you
to do is being able to move--

it's like a reflexive movement
of your head in response

to some type of visual stimulus.

For example, if I see
Kate Upton walking by,

my head is going to
move with response

to that visual stimulus.

Mm-mmm!

And then down here is
the inferior colliculi.

The inferior colliculi actually
controls reflexive head

movements or responds
to auditory stimulus.

So for example, if Kate Upton's
boyfriend yelled at me, hey,

what you doing looking
at her, my head

would move that way too.

So that's an example
of that right there.

OK, so superior colliculi,
inferior colliculi there.

All right, so if
I look here, guys,

there's another structure
I want to show you.

It's 182 right there.

That structure right there is
called the cerebral peduncles.

So it's like this stalk.

And again, these are
projection fibers actually.

So if you remember,
the cerebral peduncles,

these are projection fibers.

They're right
around the midbrain.

And they carry
sensory information up

into the cerebrum, OK?

So again, that's the cerebral
peduncles right there.

All right, guys, so if we look
here, I have 183 right there.

This is the pyramids.

This is the pyramids of
the medulla oblongata.

That's where the descending
motor fibers actually

decusse, or cross, right there.

OK?

So the pyramids is due to the
decussation, or just crossing,

of the descending
motor pathways.

All right, guys, so
if we look over here

on the side of the
medulla oblongata,

like, on this side of
this, all this pink gummy

stuff, that's all the olives.

And the olives are actually
broken up into two nuclei.

You've got their
superior olivary nuclei

and inferior olivary nuclei.

And the superior,
basically, they

play a role in basically
the auditory pathways.

And the inferior
olivary nuclei play

a role within proprioception
and cerebellum motor function

and learning and
stuff like that.

OK?

So again, olives play a
role in proprioception,

and they play a role
basically in hearing also.

All right?

So that's your olives.

Now what we're
going to do, guys,

is we're going to basically
go over the cerebellum now.

All right, guys, so if you look
here, you can see all of this,

like, tree-like
structure right there,

all this white, like,
tree-like-looking thing.

All this white matter here
is called the arbor vitae.

And the arbor vitae is just
basically the white matter

of the cerebellum.

arbor vitae actually stands
for, like, tree of life.

So again, all this white
matter here is the arbor vitae.

And the outer gray matter
on the actual edges

where you'll find, like,
your Purkinje cells

and certain stuff like
that, all the outer side

is the gray matter of
the cerebellar cortex.

And again, that's just
unmyelinated cell bodies.

Again, if you look here, in
the back of the cerebellum

here, if you see all
these little divots there,

it's actually called folia.

So the folia are basically like
the folds of the cerebellum.

OK, so all these little
lines right there

that you see forming
these little folds,

that's called the folia.

All right, guys, if you
look right here, right in

between the actual
cerebellum, there's

actually this little worm-like
structure between them.

It's actually called the vermis.

And in between the vermis,
there's an actual dural septa,

like I said before, that
actually runs in between there.

And that dural septa is actually
called the falx cerebelli.

The falx cerebelli.

OK, again, so this structure
right there between the two

cerebellum is the actual vermis.

And the dural septa that
goes between the two

is actually called
the falx cerebelli.

All right, so that pretty
much covers the cerebellum.

Now what we're
going to do is we're

going to move on to
the cranial nerves.

So if we look right here, we're
going to see cranial nerve one.

That's the olfactory nerve.

And again, remember that the
olfactory nerve originates

in the nasal cavity through
the olfactory epithelium,

and that actually picks up
certain types of sensations

like smell from odorants in
different types of chemicals

and carries that up
through the cribriform

plate of the ethmoid
bone and then up into--

specifically up into
this olfactory bulb here

where there's glomeruli
and mitral cells.

OK, so he's a sensory nerve.

Then right here, you're going
to notice two optic nerves right

there.

So there's your
left optic nerve.

There's your right optic nerve.

And then the point
in which they cross

is called the optic chiasma.

OK?

And so the optic nerve is--

basically picks up
sensations of vision.

So he picks up the
vision stimulus

and then takes that into
the actual cerebrum,

specifically to that
primary visual cortex.

Then we're going to have
to go and separate this guy

so we can look at some
other structures here,

so we look at the midbrain
a little bit deeper.

All right, guys,
so if we look here,

we can see cranial nerve 3.

It actually comes out in between
the interpeduncular fossa

right there at the midbrain.

That's called the oculomotor
nerve, cranial nerve 3.

The oculomotor
nerve actually runs

through the superior
orbital fissure

and supplies a lot of the
extraocular eye muscles.

I also didn't mention the
hole that the optic nerve runs

through, but you can imagine
it's the optic canal.

So again, oculomotor nerve runs
through the superior orbital

fissure and supplies a lot
of extraocular eye muscles.

Then if we come down here,
we can see this little--

you see this little white
thing right there, guys?

The little white piece of
thing popping down there?

That's called the
trochlear nerve.

So that's called trochlear
nerve, or cranial nerve 4.

And the cranial nerve 4,
or the trochlear nerve,

actually runs also through
the superior orbital fissure

and supplies the--

it's called the
superior oblique muscle.

It's just another
extraocular eye muscle.

OK, so he plays a role
in motor functioning.

All right, so here's the
trochlear nerve again, right?

So that's cranial nerve 4.

And then if you look down
here, we have these two nerves,

because they're paired, guys.

So we're going to see the
trigeminal nerve here,

which is cranial nerve 5.

And you'll see the
trigeminal nerve here,

which is, again,
cranial nerve 5.

So the trigeminal nerve
is a really big one,

and it actually splits
into three branches.

And it actually runs
through three holes.

It can run through the
superior orbital fissure.

It can run through the foramen
ovale and the foramen rotondum.

And the trigeminal nerve
supplies the muscles

of mastication, and
he also supplies

certain areas of the skin of
the face to pick up sensations.

So he plays a role in muscle
action, which is mastication,

chewing.

And he also picks up
sensations on the face.

Interestingly,
this is actually--

if this has what's
called neuralgia,

trigeminal neuralgia,
where there's

some certain type
of nerve pain, this

can cause one of the most severe
nerve pains actually known

to man.

It's actually called
trigeminal neuralgia.

And it's extremely,
extremely painful.

They actually call it
the suicide . disease.

All right, then if we come
down here to this structure

right there and that
structure right there,

these are actually your cranial
nerve 6, or the abducens nerve.

And he also runs through the
superior orbital fissure.

And he supplies
the lateral rectus.

And again, that's another
extraocular eye muscle.

Then if we move out
laterally over here,

we're going to have these
two guys-- see this one right

there and this one over here.

That's actually called
the facial nerve.

So that's cranial nerve 7.

So this one right there and
this one right there, OK?

And the facial nerve
has five branches.

But he can run through
the stylomastoid, foramen.

And he also can run through
the internal acoustic meatus.

But basically he supplies the
muscles of facial expression,

a lot of glands within the--
like the lacrimal gland

and nasal glands
and stuff like that.

So he plays a role in both--

and he also picks up sensations
again from the face as well.

So he's actually a motor
nerve and a sensory nerve.

OK?

So that's the facial nerve.

Then if we go over
here to the edge,

that one right there over
there and this one right there

on that edge, that is actually
called the vestibulocochlear

nerve.

And the vestibulocochlear
nerve, he also

runs through the
internal acoustic meatus.

And he basically carries dynamic
and static equilibrium and just

general sound and hearing.

And that's that guy.

Then if we come
down here, there's

this little chunk
right there, which

is the same chunk right there.

That's called the
glossopharyngeal nerve,

which is cranial nerve 9.

And he actually runs
through the jugular foramen,

and he supplies the tongue.

He supplies certain
muscles of the pharynx.

He also can act as-- he
can pick up sensations

from the baroreceptors.

So he plays a lot of roles in
different sensory and motor

functions as well.

OK?

Below him is the vagus nerve.

So this one right there
and this one right there.

That's cranial nerve 10.

So again, vagus nerve right
there and right there.

He is the main
parasympathetic nerve, OK?

He carries about 90% of
the parasympathetic flow.

And he also runs through
the jugular foramen,

and he supplies many,
many different organs

from the heart to the
lungs to the GI tract

to the urogenital tract,
so on and so forth.

So again, that's
your vagus nerve.

So if you look down
here, guys, you'll

see this nerve right
here and over here.

It's cranial nerve 11, which
is called the accessory nerve.

Now, the accessory
nerve has two parts.

One of them actually
is on the cervical part

of the spinal cord and
one on this medulla

here, like the medullary branch.

And what happens is the cervical
branch of the accessory nerve

comes up through
the foramen magnum

and merges with this
branch off the medulla.

And as a collection, they run
through the jugular foramen.

And they go and supply
the trapezius muscle

and the
sternocleidomastoid, which

are, again, those somatic
muscles or skeletal muscle.

All right, so that's
the accessory nerve.

So he's mainly a motor nerve.

And then the last one right
here is this guy right there,

which is the same as
this guy right there.

And that's cranial nerve 12,
which is the hypoglossal nerve.

And the hypoglossal
nerve actually

runs through what's called
the hypoglossal canal

and supplies some of
the extrinsic muscles

of the tongue.

OK?

So he's mainly a motor nerve.

All right, guys,
so that pretty much

covers all the cranial nerves.

I hope this video helped, guys.

And see you, ninja nerds.