What's up. Meditay here. Let's continue the anatomy of the Central
Nervous System. In this segment, we'll cover the anatomy of
the Cerebellum So the central nervous system consists of
two parts: the encephalon and the spinal cord. The encephalon is then further divided into
specific parts. We have the brainstem, which consists of the
Medulla, Pons, and the Midbrain of the mesencephalon. We have the Cerebellum back here, then the
diencephalon and the telencephalon. Our focus in this video is going to be the
Cerebellum. So in this video, we're first going to cover
the topography of the Cerebellum. Then we're gonna talk about the functions
of it. After that, we'll go ahead and take a look
at the external surface, and then make a cross-section and look at the internal surface of the Cerebellum. Basically covering the gray matter nuclei
and the white matter tracts. Alright, so we can start by replacing this
picture with a more realistic one. From here, we're able to see Pons, Medulla,
Cerebellum, and the Spinal Cord. And if we remove half of the cerebral hemisphere,
we'll see the rest of the brainstem, which is the Midbrain. So the Cerebellum mainly lies *behind*
Pons and the Midbrain, as you see here. Now, what are the functions of the cerebellum? When you're walking, the Cerebellum continuously
receives unconscious proprioception from muscles and joints, as well as receiving information
from different senses. Based upon that, it sends out motor fibers
that regulate all the muscle contractions necessary to perform your movements smoothly. So by doing that, it coordinates your balance
and posture. It regulates the tone of your muscles by passively
contracting the muscles to ensure joint stability. And it also smoothens voluntary movements
of muscles. So when you write. Here most of the fibers come from the cerebral
cortex since this is a voluntary movement. But these movements are able to be smooth
and precise by the Cerebellum engaging its fibers into the muscles necessary to stabilize
the movements. So these are the top three functions the Cerebellum
has. Let's now finally understand the actual anatomy
of it by looking at the external structures. So here's a posterior view of the Cerebellum. If we isolate the Cerebellum and the brainstem,
you'll be able to see the rest of the Cerebellum. The Cerebellum consists of two hemispheres
on either side and a vermis in the middle. And if you look closely at the surface of
the Cerebellum, you'll see grooves and bumps on it. These grooves are called sulci of the Cerebellum. And between them, you'll see the Folia of
the Cerebellum, which are the small bumps between the sulci. You'll also be able to see some deeper grooves
on the surface, which we call fissures. The first one is a very prominent one called
Primary Fissure, And this fissure marks the separation between
the Anterior Lobe of the Cerebellum and the Posterior Lobe of the Cerebellum. So this is a posterior view, but if you look
at the cerebellum from an anterior view as well, you'll see another deep fissure, called
Posterolateral fissure which separates the posterior lobe from the flocculonodular lobe. It's kind of a tongue twister, but it consists
of two parts. The Nodular part and the floccular part. That's why we call it the Flocculonodular
lobe. From the anterior view of the cerebellum,
we can also see the Cerebellar Peduncles. The cerebellar peduncles connect the Cerebellum
with the brainstem. So if we remove the Cerebellum, you'll find
the cerebellar peduncles here on the anterior view of the brainstem. So again, this is Pons, This is the Medulla,
and this is the Mesencephalon. On either side of the brainstem, you'll see
the cerebellar peduncles, which contain fibers that run between the Cerebellum and all three
parts of the brainstem. The inferior cerebellar peduncle contains
fibers that go to the Medulla. The middle cerebellar peduncle contains fibers
that go to Pons. The superior cerebellar peduncle contains
fibers that go to the Midbrain. So that was the main external anatomical structure
of the Cerebellum. Let's now take the Cerebellum and give it
a good slice like this. And then look at it from this perspective. We'll see this. So this is a scheme I made in order to make
it easier to understand the internal structures of the Cerebellum. We can see the two hemispheres of the Cerebellum
on either side and the Vermis of the Cerebellum in the middle. Vermis literally means worm because it looks
like a worm between the hemispheres. Alright. Let's first add the white matter of the Cerebellum
so that it's easier to distinguish the grey matter from the white matter. Remember, White matter contains myelinated
nerve fibers, so when we talk about white matter, we mainly talk about tracts. Gray Matter contains nuclei of neurons, so
when we talk about the gray matter, we mention nuclei. Let's first go through the Gray matter of
the Cerebellum and then do the white matter. So the gray matter of the Cerebellum is mainly
located at the surface and forms the cortex of the Cerebellum of the cerebellar cortex. It's a dense cortex that consists of three
layers with nuclei. The Cerebellum is also going to have gray
matter within the actual Cerebellum in between the fibers of the white matter. And the first one is the dentate nucleus,
which takes part in the unconscious coordination of your muscles through the corticopontine
tract. I'll show you later in this video when we
go through the tracts. Then we have the fastigial nucleus. And one thing it's responsible for is, remember
the inner ear consists of the cochlea and the vestibulum? The vestibular system has these semicircular
canals that sense the movements of the head, whether it's horizontal movement or vertical
or angular movement. They will stimulate the vestibular nerve,
which will travel towards the vestibular neurons of Pons, where two things will happen. One. It will send a vestibulospinal tract towards
your muscles to maintain a balance. But from the vestibular nuclei, a vestibulocerebellar
tract will also go to the Cerebellum and synapse with the fastigial nucleus. This is to engage the Cerebellum in helping
with balance and posture. Because remember, the Cerebellum is the master
of unconscious proprioception, and It knows exactly where your arm is and where your legs
are all the time. So that is this one. Next, there are the globose nucleus and the
emboliform nucleus. Remember when we talked about the spinal cord,
there were the anterior and the posterior spinocerebellar tracts? The fibers from the posterior spinocerebellar
tract will go directly to the Cerebellum through the inferior cerebellar peduncle, and fibers
from the anterior spinocerebellar tract will go up through Pons and the Midbrain, and then
to the Cerebellum through the superior cerebellar peduncle, to then synapse with the emboliform
and the globose nuclei. These are sensory fibers for unconscious proprioceptive
sensation. They will give sensory input about posture
and joints and then provide stability by passively contracting the muscles around the joints. It also provides sensory input from the surrounding
area, which is a part of the feedforward control. So that is the grey matter of the Cerebellum. Take a mental picture of this, and let's go
over and do the white matter. The white matter of the Cerebellum consists
of tracts. But one thing that is very characteristic
for the Cerebellum is the white matter branching out towards the cortex to resemble branches
of a tree. We call this the tree of life, or arborvitae. And it's very prominent. If you look at the Cerebellum, these beautiful
branching patterns are very characteristic for the Cerebellum, as you see here. It resembles the branching of a tree, and
because the Cerebellum has crucial functions in our body, it's called the tree of life. So the white matter contains tracts that go
in and out of the Cerebellum. And they do that through these peduncles. The superior peduncle between the Midbrain
and the Cerebellum, the middle cerebellar peduncle between Pons and the Cerebellum,
and the inferior cerebellar peduncle, between the Medulla and the Cerebellum. To visualize this in an easier way, I've made
this scheme that shows the Cerebellum here in green. And we can see the superior cerebellar peduncle,
the middle cerebellar peduncle, and the inferior cerebellar peduncle going between the Cerebellum
and the brainstem. I've also divided this model into two sides. The right side will show fibers that enter
the cerebellum, called afferent fibers, or sensory fibers. And the left side will illustrate fibers that
leave the cerebellum, called efferent fibers, or motor fibers. The first tract t is a tract we mentioned
earlier. So from the vestibular system of the inner
ear, we got the Vestibular nerve going towards the vestibular nuclei of the rhomboid fossa,
in Pons. Some fibers from the vestibular nuclei will
pass posteriorly, and then through the inferior cerebellar peduncle, towards the Cerebellum. And remember, the vestibular system is for
balance. So that is this one. The next tract is also one we mentioned earlier. And that is the spinocerebellar tracts that
receive information about unconscious proprioception. So if we add the CNS to illustrate. The posterior spinocerebellar tract will enter
the Cerebellum through the inferior peduncle. And the anterior spinocerebellar tract will
ascend up through Medulla and Pons and the Midbrain, ad then through the superior peduncle
and into the Cerebellum. So again, posterior spinocerebellar through
the inferior peduncle. And the anterior spinocerebellar through the
superior peduncle. Next is a tract you hear about a lot when
you study the central nervous system. So here we have a cross-section of Pons and
the Medulla Oblongata. Sensory fibers from the lower part of your
body will go to the spinal cord and from the Gracile Fascicle. Fibers from the upper part of your body will
go to your spinal cord and form the Cuneate Fascicle, which is lateral to the gracile
fascicle These two fibers will go up and synapse with
the Cuneate nucleus and the gracile nucleus of the Medulla, as you see here. And then, from here, two things will happen. Fibers will cross internally as the internal
arcuate fibers and then ascend as the medial lemniscus. Or they will leave the brainstem as the external
arcuate fibers through the inferior cerebellar peduncle. And that is another tract we can add to this
scheme, the external arcuate fibers. Then there are fibers that originate from
the olivary nucleus of the medulla. These fibers cross the Medulla and then go
through the inferior cerebellar tract towards the Cerebellum. Then there is the corticopontine tract. This tract includes the frontopontine fibers,
parietopontine fibers, temperopontine fibers, and occipitopontine fibers. Basically, all the fibers coming from the
different lobes of the cerebral cortex to the Pons are grouped as the corticopontine
tract. They will descend to Pons and synapse with
the pontine nuclei. And then they go from the Pontine nuclei to
the Cerebellum. So here are the pontine nuclei. They cross Pons and go through the middle
peduncle to the Cerebellum. From the Cerebellum, fibers go up towards
the nucleus ruber in the Midbrain, as you see here. As the cerebellorubral tract or the Dentatorubral
tract because they synapse with the dentate nucleus of the Cerebellum. And then from the red nucleus, the tract will
descend as a rubrospinal tract. Notice that none of the corticopontine tracts
came from the pyramidal cells of the primary motor cortex. They came from all other regions of the cerebral
cortex. That means that this is an extrapyramidal
tract, so this tract engages the Cerebellum in coordinating and helping with smooth and
precise voluntary movements. So that was all I had for the anatomy of the
cerebellum. If you found this video helpful, don't forget
to like, comment, share, whatever you find convenient. And I hope this was helpful.