Test your understanding with 10 random multiple-choice questions from the question bank.
This video compiles all the cranial nerve schemes shown in previous videos into one comprehensive guide. It is designed to help you study each cranial nerve more efficiently by summarizing their pathways, functions, and anatomical details. Whether you’re preparing for an exam or simply reinforcing your knowledge, this video serves as a quick and effective study tool. Hope it helps! 😊
This video covers:
Used under licensed permission.
Introduction
0:00
Alright so I’m making this video just to give you a quick repetition of each cranial nerve. I’m not gonna talk about all the canals and branches in detail, we already
0:08
talked about then in the 12 previous videos. This video is dedicated to basically give you one place where you’ll find all the schemes for each cranial nerve. So this video
0:18
might be a little long, but I promise if you know all these schemes, you basically have a good grasp of each cranial nerve. And what I recommend you is to redraw each of these
0:27
schemes several times until you can recall them easier. That’s what I did when I had to memorize them. Knowing these schemes will guarantee you enough knowledge on each cranial
0:36
nerve. Now before I start, I want you to understand a concept regarding the cranial nerves, a general division of the cranial nerves that
Cranial Nerve Fibers
0:45
will help you make sense out of how the fibres are distributed. A cranial nerve can have motor fibers, sensory fibers, or parasympathetic motor fibers.
0:55
So cranial nerves can be sensory, motor or mixed nerves. They’re called mixed nerves
1:00
if they have both sensory and motor functions. Cranial nerve motor are further subdivided
1:06
into functional components according to their targets. So they can be General Somatic Efferent
1:13
(GSE), supplying skeletal muscles of somatic origin like the extraocular muscles. It can
1:18
be Special Visceral Efferent (SVE), supplying skeletal muscles derived from the pharyngeal
1:23
arch like the facial muscles, and General Visceral Efferent (GVE) fibres, giving off
1:28
preganglionic fibres to ganglia that contribute to the cranial parasympathetic outflow. Postganglionic
1:36
fibres of those peripheral ganglia further supply the smooth muscles and glands of various
1:41
organs and salivary glands. Sensory fibres are further subdivided according
1:46
to where the sensations are coming from, so it’s subdivided as Visceral or Somatic,
1:52
and visceral is further subdivided into general and special. So sensory fibres are classified as General visceral afferent fibers (GVA), that convey
2:01
visceral information like distention of organs and chemical conditions from the blood vessels,
2:06
heart, lungs, digestive system and so on. There’s the Special visceral afferent (SVA),
2:11
that carry the special sense of taste. And General somatic afferent (GSA), that bring
2:17
in primarily sensations like pain, temperature, touch, vibration, and pressure from skin,
2:23
and also proprioreceptors localized in the muscles, joints and ligaments. So this is how we divide cranial nerve fibres. Let’s now start off with the olfactory nerve.
CN 1 Olfactory Nerve
2:34
The olfactory nerve conducts the sensation of smell to the brain via the olfactory bulb
2:39
and tract. Here we got any sort of smell around your environment. These gaseous odorants will eventually reach your olfactory nerves at the superior
2:48
part of your nasal cavity. These nerves are going to run together through the cribriform
2:53
plate, and then synapse with neurons in the olfactory bulb, forming those glomeruli. The
2:59
olfactory bulb continues posteriorly as the olfactory tract, which is going to run towards
3:04
the olfactory trigone, which is a small triangular area in front of the anterior perforated substance.
3:10
The olfactory tract now divides into striae. It divides into the medial stria, the lateral
3:16
stria, and in some cases the intermediate stria, which extend into the anterior perforated
3:21
substance and ends in a slight elevation called the olfactory tubercle. The lateral stria
3:28
terminates in the primary olfactory cortex of the temporal lobe, while the medial stria
3:33
passes to the contralateral olfactory tract and terminates in the limbic structures to contribute to the emotional responses brought on by the smell.
3:42
Alright so that is the general outline of this nerve. If you know this, you basically know the most important parts of the olfactory nerve.
CN 2 Optic Nerve
3:49
Let’s now do the second cranial nerve, the optic nerve. The optic nerve carries visual information to the brain via the optic tract.
3:58
Our vision starts at the eye, specifically the retina. The visual pathway consists of
4:04
4 different neurons. The first, second and third order neurons are in the retina of the
4:10
eyeball. So, 1st order neuron represents the rods and cones in the retina, 1st order means
4:16
this is where light is made into nerve signals, the start of the pathway basically. Signals
4:22
then go to 2nd order neurons which are the bipolar cells of the retina, then towards
4:28
the 3rd order neuron, the ganglion cells of the retina. The visual stimuli are then sent
4:34
through the optic nerve, which goes through the optic canal. The optic nerve then crosses
4:39
with the optic nerve of the other eye to then continue as the optic tract. So, half the
4:45
fibres go to the contralateral side, and half the fibres continue in the ipsilateral side
4:50
together with fibres from the other eye. The optic tract then goes on and synapses with
4:56
the fourth order neurones in the lateral geniculate body of the metathalamus. These neurones then
5:02
take visual information from the retina to the primary visual area in the occipital lobe.
5:08
There are collateral branches that go towards the midbrain aswell responsible for the pupillary light reflex, but for the sake of simplicity since this is a summary video, we’ll end
5:18
the scheme like this. So that was the 2nd cranial nerve. The 3rd cranial nerve is the oculomotor. The oculomotor nerve allows movement of the
CN 3 Oculomotor Nerve
5:29
eye muscles, constriction of the pupil, and the position of the upper eyelid. Let’s
5:34
see how. There are two nuclei for the oculomotor nerve that are both located in the midbrain at the level of the superior colliculi. Those are
5:42
called the nucleus of the oculomotor nerve and the accessory oculomotor nucleus. The
5:48
oculomotor nucleus is a motor nucleus or what we call general somatic efferent nuclei. While
5:55
the accessory is indicated in purple, so it’s parasympathetic, or what we call general visceral
6:01
efferent nucleus. Those two nuclei are gonna give off fibres that are going to meet, and
6:07
run together as something called the oculomotor complex. It’s going to go out of the midbrain
6:13
through the oculomotor sulcus, from the anterior side. It then run laterally in the wall of
6:19
the cavernous sinus, and then enters the orbit through the superior orbital fissure, into
6:24
a ring called the common tendinous ring, and then it splits into a superior branch and
6:30
an inferior branch. The superior branch will innervate the levator palpebrae muscle, and
6:35
the superior rectus muscle. The inferior branch will innervate the Medial rectus, Inferior
6:41
rectus and the inferior oblique. The superior and the inferior branch are the somatomotor
6:48
fibres of the oculomotor nerve complex, meaning they innervate the extraocular muscles. The
6:54
remaining fibres are parasympathetic fibres coming from accessory oculomotor nucleus.
7:00
The parasympathetic fibres runs together with the inferior branch, and then goes out towards
7:06
the ciliary ganglion. The ciliary ganglion then gives off small ciliary nerves which
7:13
innervate the ciliary muscle for accomodation, changing the shape of the lens to focus the
7:18
eye on near objects basicaully. And it innervates the sphincter pupillae, which constricts the
7:24
pupil, causes miosis. Alright so this is the general overview of the oculomotor nerve.
7:29
Let’s now do the 4th cranial nerve. The fourth cranial nerve is the trochlear nerve.
CN 4 Trochlear Nerve
7:35
The trochlear nerve innervates the superior oblique muscle to move the eye in a down-and-out
7:41
position, and intort the eye. The nerve starts from a nucleus called the nucleus of the trochlear nerve. It also goes to the eye muscles, so it give off general
7:51
somatic efferent fibers. It’s located in the midbrain at level of the inferior colliculus,
7:56
so inferior to the motor nucleus we talked about earlier. Form the nucleus of the trochlear
8:02
nerve, the motor neuron will leave from the posterior surface of the midbrain, turn anteriorly
8:08
and run on the lateral wall of the cavernous sinus. It then enters the orbit via the superior
8:14
orbital fissure, to innervate the superior oblique. So that was this one. Next one up is the trigeminal nerve.
CN 5 Trigeminal Nerve
8:23
This nerve is primarily responsible for the sensory innervation of the face, and motor
8:28
control of the muscles involved in mastication, or chewing. Right?
8:34
It starts with three sensory nuclei, called mesencephalic, principal and the spinal nuclei
8:39
of the trigeminal nerve, and one motor nucleus, all located within the brainstem. The sensory
8:46
nuclei receive general somatic afferent fibers, while the motor nucleus of the trigeminal
8:52
give off special visceral efferent fibers, which basically supply skeletal muscles derived
8:58
from the pharyngeal arches, like the muscles of the face. The sensory nuclei all have a sensory root that comes from the trigeminal ganglion. There
9:08
are three divisions coming in towards the trigeminal ganglion. We got the ophthalmic,
9:13
for the forehead and eyes, maxillary for the region of the middle face. And the mandibular,
9:19
for the lower Face and jaw. The motor fibres which will join the mandibular division, to
9:24
innervate primarily the muscles of mastication. The ophthalmic nerve will go through the superior
9:31
orbital fissure, but give off a tentorial nerve before it enters, providing sensory
9:36
innervation to the dura mater of the middle cranial fossa. Once the ophthalmic nerve goes
9:42
through the superior orbital fissure, it receives three fibers. Nasociliary, frontal, and lacrimal
9:49
nerves. The frontal nerve goes directly beneath the roof of the orbit, and extends into two
9:55
terminal division, called supraorbital nerve and the supratrochlear nerve. The supraorbital
10:00
nerve goes up towards the forehead, where it splits into two of its own terminal branches.
10:07
The lateral and medial branch. The nasocilliary will go through the common
10:12
tendinous ring, and splits into the posterior ethmoidal nerves that innervates the mucosa of the ethmoid cells and sphenoid sinus. There’s the anterior ethmoid nerves that innervates
10:23
the roof of the nasal cavity. We got long ciliary nerves for the eyes, and the infratrochlear
10:29
nerve for the upper eyelid and the conjunctiva. The last nerve is the lacrimal nerve going
10:35
to the lacrimal gland and the upper eyelid. The maxillary nerve will go through the foramen
10:41
rotundum, but before that it’ll give off a meningeal branch for the dura of the middle
10:46
cranial fossa. Once it enters the pterygopalatine fossa, it gives off 2-3 nerves to the pterygopalatine ganglion. Then it gives off three branches.
10:58
The posterior superior alveolar nerve, Infraorbital nerve, and the zygomatic nerve. The zygomatic
11:05
and the infraorbital nerves will enter the orbital cavity through the inferior orbital fissure. The zygomatic nerve then give off two branches, the zygomaticotemporal branch
11:16
and the zygomaticofacial branch, which both run through their own respective foramina.
11:22
The infraorbital nerve will run on the floor of the orbital cavity, and on it’s way,
11:27
it’ll give off the middle superior alveolar nerve and the anterior superior alveolar nerve.
11:34
Then the nerve goes through the infraorbital groove, and give off three branches. It gives
11:39
off the inferior palpebral nerve, the nasal branches and the superior labial branches
11:45
for the upper lips. The third branch here is the posterior superior
11:50
alveolar nerve. So that’s the big part of the maxillary nerve. Other branches in respect to the pterygopalatine ganglion, are the pharyngeal nerve and the
11:59
nasopalatine nerve. We got the lesser palatine for the soft palate and the greater palatine
12:04
for the hard palate. There are some other couple of branches here too but I’m only focusing on some important ones to not make this too overwhelming.
12:13
The pterygopalatine ganglion is gonna give off postganglionic parasympathetic fibers
12:19
that run together with the zygomatic nerve, which goes towards the lacrimal nerve as a communicating branch, that provide parasympathetic innervation to the lacrimal gland.
12:28
Alright. Let’s do V3, the mandibular. Notice how motor fibres from the motor nuclei passes
12:35
below the trigeminal ganglion without synapsing with it, and joins the sensory root of the
12:41
nerve. This nerve will leave the neurocranium through the foramen ovale. And just as it
12:47
leaves, it gives off the meningeal branch, which goes back into the neurocranium through
12:52
the foramen spinosum. Keep in mind there might be some variations here but we’ll keep it
12:57
at that. It then give off the auriculotemporal nerve, which is composed of two roots that encircling the middle meningeal artery, to supply the
13:05
ear and the temporal region. One of the parasympathetic ganglions in our cranium is called the Otic
13:12
ganglion. The otic ganglion is going to receive parasympathetic fibers from the glossopharyngeal
13:17
nerve, which is going to give off postganglionic parasympathetic nerve fibres that join and
13:23
“hitch-hike” along the auriculotemporal nerve to innervate the parotid gland. There’s a lingual nerve, which is sensory for the anterior ⅔ of the tongue. There’s
13:33
the inferior alveolar nerve, which split into the nerve of the mylohyoid muscle. The sensory
13:40
part enters the mandibular foramen, and reach the mandibular canal. Within the mandibular
13:46
canal, it give off branches to supply the teeth of the mandible. Henche the name inferior
13:51
alveolar. The nerve then passes the mental foramen to terminate on the face and innervate
13:57
the lower lip, now called the mental nerve. Then we have a buccal nerve, which innervates
14:03
the skin of the cheek and buccal mucosa. And then we got all these muscular branches
14:08
responsible for different functions, primarily mastication. So that is the scheme for the
14:14
trigeminal nerve. Let’s do the abducent nerve. Alright, so the abducent nerve is a purely motor nerve, supplying the lateral rectus
CN 6 Abducent Nerve
14:22
muscle involved in abduction of the eye. It starts off with the nucleus of the abducent
14:28
nerve in Pons, which give off motor fibers. The nerve will travel through the junction
14:33
between the medulla and pons. It’ll pierce the dura mater and travel through the cavernous sinus, then it’ll go through the superior orbital fissure, and the common tendinous
14:44
ring, where it’ll innervate the lateral rectus muscle. That’s really all for this one. Let’s do the facial nerve.
CN 7 Facial Nerve
14:51
The facial nerve is responsible for providing motor innervation of the facial muscles, as
14:57
well as taste from the anterior two-thirds of the tongue and producing saliva and tears.
15:03
Whitin Pons and the upper parts of the medulla, we will find the motor nucleus, which sends
15:08
out motor fibres or Special visceral efferent fibers. We got the superior salivatory nucleus,
15:15
which sends out fibres to the salivary and the lacrimal glands, we call these general visceral efferent nuclei. Then we got some sensory fibres coming in synapsing with the
15:26
spinal nucleus of the trigeminal nerve, and the nuclei of the solitary tract.
15:31
These fibres go between Pons and the Medulla, and then from two roots. A motor root, and
15:37
a smaller sensory root. The motor root will travel through the Internal acoustic meatus
15:43
and enter the facial canal. In the facial canal, the facial nerve bends at the area
15:49
where the geniculate ganglion is located. In the posterior wall of middle ear, it gives
15:54
off the nerve to stapedius, then it continues downwards towards the stylomastoid foramen.
16:01
The superior salivatory nucleus will give off fibers that’ll also go through the geniculate
16:06
ganglion without synapsing with it, and give off the greater petrosal nerve. On its course
16:12
towards the foramen lacerum, it merges with the deep petrosal nerve carrying sympathetic
16:17
fibres to form the nerve of the pterygoid canal. It travels to the pterygopalatine ganglion
16:24
to provide preganglionic parasympathetic innervation to the lacrimal gland as well as mucous glands
16:31
of the nasal cavity, maxillary sinus and palate. Fibers from the superior salivary nucleus
16:38
will also branch off and give a nerve called chorda tympani. Chorda tympani exits the skull
16:44
by passing through the petrotympanic fissure, to enter the infratemporal fossa, and terminate
16:50
as the submandibular ganglion, which then sends off postganglionic fibers to innervate
16:55
the submandibular and the sublingual salivary glands. Chorda tympani consists of two fibers,
17:02
general visceral efferent fibres here in purple, which come from the superior salivatory nucleus.
17:08
The other component are special visceral afferent fibers, coming from the taste receptors of
17:14
the anterior 2/3 of the tongue, then travels to synapse with sensory nuclei in the geniculate
17:20
ganglion, which then sends fibres towards the nucleus of the solitary tract. A component
17:26
of the facial nerve also provides sensory innervation around the external acoustic meatus
17:32
and the retro auricular region. These general somatic afferent fibres travel through the
17:38
stylomastoid foramen to also synapse with their respective nuclei in the geniculate
17:43
ganglion, which then sends off fibres towards the spinal nucleus of the trigeminal nerve.
17:49
The motor fibres, or special visceral efferent fibres are going to leave the canal through
17:54
the stylomastoid foramen. It then gives off the posterior auricular nerve, which branches off as the occipital and the auricular segments to innervate the
18:03
occipitofrontalis muscle, and the intrinsic muscles of the ear. It’ll also give off
18:09
a stylohyoid branch and a digastric branch, for the respective muscles. The facial nerve
18:14
then continues into the parotid gland, branching off forming the parotid plexus, which is a
18:20
plexus of nerves that give off a superior branch and an inferior branch. The superior
18:26
branch give off the Temporal, Zygomatic and the Buccal branches. While the inferior branch
18:31
give off the marginal mandibular and the cervical branch, all of these supply different muscles
18:36
of the face. So that was this nerve. Now let’s do the
CN 8 Vestibulocochlear Nerve
18:41
vestibulocochlear nerve. The vestibulocochlear nerve is purely a sensory nerve. It has no motor function. And it consists of two parts. A vestibular part, which is
18:52
responsible for maintaining a sense of equilibrium and balance. And it has a cochlear part, which
18:57
facilitates hearing. We’ll start this scheme off by adding the membranous labyrinth of the inner ear. From the coclear part of the inner ear, there will
19:07
be dendrites of nerves located within the organ of corti, in the cochlea. These dendrites
19:13
take signals towards the spiral ganglion, from where axons then run as the coclear root.
19:19
From the vestibular part of the inner ear, you’ll find nerve endings coming from the saccule and one coming from the posterior ampullary crest. They two form an inferior
19:30
division. Then we got a nerve coming from the macula of the utricle, and two other nerves
19:36
from the lateral and the anterior ampullary crests. They form the superior division.
19:42
The superior and the inferior divisions will take the signals towards the vestibular ganglion.
19:49
Axons from the ganglion leave as the vestibular root. The vestibular root and the cochlear
19:54
root now travel together as the vestibulocochlear nerve, and they’re going to leave through
19:59
the Internal acoustic meatus. This nerve will now enter the brainstem through
20:04
the pontomedullary junction, and separate as the cochlear nerve and the vestibular nerve.
20:10
The cochlear nerve will run off and synapse with the ventral and the dorsal cochlear nuclei.
20:16
The Vestibular nerve will reach the vestibular nuclear complex, consisting of the superior,
20:21
medial, lateral, and the inferior part. The medial nucleus sends off ascending fibres
20:27
to the motor nuclei of the extraocular muscles ipsilaterally and contralateral via the medial
20:33
longitudinal fasciculus (MLF), which helps facilitate the vestibulo-ocular reflex. Some
20:39
fibres come from the superior nuclei as well but for the majority of it, we associate the
20:44
MLF with the medial vestibular nucleus. The medial nucleus also give off the medial vestibulospinal
20:51
tract, while the lateral nucleus will give off the lateral vestibulospinal tract. The
20:57
lateral vestibulospinal tract goes down ipsilaterally for the body and limb, and the medial vestibulospinal
21:03
tract is a part of the MLF, going down both ipsilaterally and contralaterally to control
21:10
the head and neck movement. The inferior vestibular nucleus sends fibers
21:15
towards the cerebellum through the inferior cerebellar peduncle for the vestibulocerebellar
21:20
system. Fibers also can come directly from the vestibular nerve before it enters the
21:26
brainstem. This is a two way connection, so fibers will also come from the cerebellum
21:31
and then into the vestibular nucleus again, to help influence the vestibulospinal tracts.
21:38
Then we got fibers that go all the way up to the Ventral Posterior group of thalamus.
21:44
These are fibers that primarily come from the superior vestibular nuclei. They then
21:49
project to the internal capsule and further radiate into different areas of the cerebral
21:54
cortex. It could be to the primary somatosensory cortex to map the body location and movement
22:00
signals, it could be the frontal eye fields to control the eye movement and receive vestibular motion information. Could be the hippocampus and the parahippocampal area for spatial orientation
22:10
and navigation. Parieto-Insular cortex which responds to the body and head motion information,
22:18
and the posterior parietal cortex aswell. For the Cochlear part information is going
22:23
to cross and ascend as the lateral lemniscus. But they can also go ipsilaterally and ascend.
22:30
They may synapse with the superior olivary complex, which plays a role in localizing the direction of sound. Cochlear fibers may synapse with cells that lie within the lemniscus
22:41
itself, which form the nucleus of the lateral lemniscus. As fibers from both sides cross,
22:48
they form a mass of fibers called the trapezoid body, containing cell bodies with nuclei which
22:54
the cochlear nerve may also synapse with. The lateral lemniscus will go up and synapse
22:59
with the inferior colliculus. From here fibers may go down as the tectospinal tract, which
23:06
plays a role in the auditory reflexes. Fibers may also go up through the brachium of the
23:12
inferior colliculus, towards the medial geniculate body next to the thalamus. It can also receive
23:18
fibers directly from the lateral lemniscus aswell. Then it’ll radiate towards the superior
23:24
temporal gyrus which is believed to be the primary auditory cortex. So. That was the
23:30
scheme for the vestibulocochlear nerve. Almost done, 9th cranial nerve.
CN 9 Glossopharyngeal Nerve
23:36
The glossopharyngeal nerve plays a crucial role in transmitting sensory information from the back of the throat, taste sensations and saliva production, and is involved in swallowing
23:47
and speaking. This nerve has the nucleus ambiguou Inferior salivatory nucleus which is parasympathetic, nucleus of solitary tract which is functionally
23:56
divided into a viscerosensory part and a gustatory part for taste. And we got the spinal nucleus
24:02
of the trigeminal nerve which is somatosensory. Nerves are going to go in and out through
24:08
the medulla, on the lateral aspect of the olive. So, It has a motor component, parasympathetic
24:14
component, and the sensory components. The motor part will go through the jugular foramen,
24:20
through the superior and the inferior ganglion of the glossopharyngeal nerve, then it’s going to go and innervate the stylopharyngeus muscle. The parasympathetic component is going
24:30
to go through the jugular foramen and give off the tympanic nerve. The tympanic nerve
24:35
is going to go through the tympanic cancliculus and then enter the tympanic cavity.
24:40
Within the tympanic cavity, it’s going to form the tympanic plexus, which is also formed by the sympathetic caroticotympanic nerves that extend from the internal carotid plexus.
24:52
From the tympanic plexus, there is a parasympathetic branch that’s going to out called the lesser
24:58
petrosal nerve. It goes through the canal of the lesser petrosal nerve and leaves the cranium as it passes though the sphenopetrosal fissure, or foramen ovale, or petrosal foramen,
25:10
there are variations to this nerve on how it exits the skull, but primarily I think most sources say the foramen ovale. But what you need to know is that this nerve will provide
25:19
preganglionic parasympathetic innervation to the otic ganglion, which then form postganglionic
25:26
parasympathetic fibers that run together with the auriculotemporal nerve of the trigeminal
25:31
nerve, to innervate the parotid gland and make it salivate.
25:36
For the sensory part – There are fibers that come from the carotid body and sinus, from the baroreceptors and chemoreceptors there. They’re going to go take these impulses
25:45
towards the inferior ganglion of the glossopharyngeal nerve, and then go synapse with the nucleus
25:51
of the solitary tract. Then there are some special sensory fibers for the sense of taste
25:56
from the posterior one-third of the tongue. These fibers are going go towards the inferior
26:02
ganglion, then towards the gustation part of the solitary tract. The last fibers which
26:08
I’ve highlighted in green here are somatic sensory fibers innervating mucosal membranes
26:13
along different regions. There are general sensory fibers coming from the posterior 1/3
26:19
of the tongue, and taking these impulses towards cell bodies in the superior ganglion of the
26:25
glossopharyngeal nerve. Then towards the spinal nucleus of the trigeminal nerve. So we got
26:31
two fibers now from the posterior 1/3 of the tongue. One part for taste and one part for
26:37
general sensory like touch, pain and temperature. Then there’s a branch coming in along the
26:42
tympanic nerve from the mucus membranes of the middle ear, tympanic membrane and part of the external ear. Then there’s a large area in the pharyngeal
26:52
region that is supplied by this nerve, though the pharyngeal plexus. This plexus is formed
26:57
from the union of branches from the vagus nerve, laryngopharyngeal nerves from the cervical
27:02
sympathetic plexus, and the glossopharyngeal nerve. They’re also going to go towards
27:07
the superior ganglion and then to the spinal nucleus of the trigeminal nerve. There’re
27:14
also fibers coming from mucus membranes of the palatine tonsils. So that was this nerve, now let’s do the vagus nerve, the 10th cranial nerve.
CN 10 Vagus Nerve
27:24
The vagus nerve has the longest course of all the cranial nerves, extending from the head to the abdomen. It has a parasympathetic component, which help regulate functions like
27:34
the heart rate, digestion, and respiratory rate. It has sensory component to relay information
27:40
from various visceral organs, and a motor component for tasks like speech and swallowing.
27:45
This nerve has altogether 4 nuclei that are located within the medulla oblongata. We got
27:51
a nucleus ambiguous, Posterior nucleus of the vagus nerve, which is parasympathetic,
27:56
nucleus of solitary tract and the spinal nucleus of the trigeminal nerve. Nerves are going
28:02
to go in and out through the medulla on the lateral aspect of the olive. So It has a motor
28:08
component, parasympathetic component, and the sensory components. Some important landmarks
28:13
to put in here are the jugular foramen, superior ganglion of the vagus nerve, and the inferior
28:19
ganglion of the vagus nerve. The first branch we’ll start off with is the auricular branch,
28:25
which gathers sensations from the skin of the anterior auricle, external acoustic meatus,
28:30
and the external surface of the tympanic membrane. The auricular branch will go through the mastoid
28:36
canaliculus and then synapse with nuclei located within the superior ganglion, and then directly
28:42
to the spinal nucleus of the trigeminal nerve. Another sensory nerve is the meningeal branch,
28:49
which arises at the at the superior ganglion and re-enters the skull via the jugular foramen
28:55
to innervate the dura of the posterior cranial fossa. Also taking sensory information towards
29:00
the spinal nucleus of the trigeminal nerve. Now, from here we’re going to do a couple
29:06
of branches together since most branches of the vagus nerve consists of a combination of parasympathetic, motor and sensory innervations. So the motor component coming from the nucleus
29:18
ambiguous will go through the jugular foramen and the ganglia without synapsing with them.
29:23
Then it’s going to take a turn towards the pharynx to contribute to the pharyngeal plexus, together with the glossopharyngeal and the laryngopharyngeal nerves. So the vagus nerve
29:33
here represents the motor component of the pharyngeal plexus and ultimately provides
29:38
motor innervation to most of the muscles of the soft palate (all but the tensor veli palatini
29:43
muscle), and of the pharynx (all but the stylopharyngeus muscle). Around at the level of the inferior ganglion, the cranial component of the 11th cranial
29:53
nerve, the accessory nerve, is going to supply motor fibres into the vagus nerve, and further
29:58
towards the pharyngeal plexus. Which means that the 11th cranial nerve is going to help
30:03
the vagus nerve innervate most pharyngeal and soft palate muscles, both coming from
30:09
parts of the nucleus ambiguous in the brainstem. Together with the pharyngeal branch, there
30:14
are going to be sensory taste fibres, sensing taste at around the region of the epiglottic
30:19
valleculae, which are going to synapse with nuclei whithin the inferior ganglion, to further
30:25
send information towards the nuclei of the solitary tract. So the pharyngeal branch contain
30:31
sensory visceral efferent fibers which are motor, and special visceral afferent fibers,
30:37
for taste. The motor fibers are going to continue and give off branches forming the superior laryngeal nerve, which also contain general visceral
30:47
afferent fibers that synapse with nuclei in the inferior ganglion and then to the nuclei
30:53
of the solitary tract. The pharyngeal nerve is now going to split into an external branch and an internal branch. The external branch is primarily going to
31:03
innervate the cricothyroid muscle, for phonation. The internal fibres are going to contain a
31:09
little bit of parasympathetic fibres as well coming in from the posterior nucleus of the vagus nerve. And they’re going to provide sensory innervation to the laryngeal mucosa
31:18
above the vocal cords, epiglottis and the root of the tongue, and parasympathetic innervation
31:24
to glands and vasculature in the same area. Further down the line we got the recurrent
31:29
laryngeal nerve, which leaves the nerve at the region of the neck, goes down to the thorax
31:35
to loop around the subclavian artery on the right side, and the aortic arch on the left side, and then they travel back up along the neck. On its way, it’s going to give off
31:46
branches to the trachea, providing parasympathetic fibers aswell for the mucosal lining of the
31:51
trachea and mucosal glands and smooth muscles in the same area. We have esophageal branches,
31:57
which provide motor innervation to striated muscles of the esophagus, sensory innervation
32:02
to the mucosa and parasympathetic innervation to the glands and smooth muscle of the esophagus.
32:08
It’s also going to provide motor innervation to the inferior pharyngeal constrictor muscle,
32:14
and a little bit of sensory innervation to the pharyngeal area as well. The recurrent laryngeal nerves are then going to go up towards the larynx and terminate
32:23
as the inferior laryngeal nerve. The inferior laryngeal nerve has a sensory component innervating
32:29
the laryngeal mucosa below the vocal cords, and a motor component innervating the intrinsic
32:35
muscles of the larynx, except the cricothyroid. The accessory nerve might also travel with
32:41
the recurrent laryngeal to help innervate the intrinsic muscles of the larynx as well.
32:47
As the inferior laryngeal nerve ascends, it’s going to form some synapsing fibres with the
32:53
internal branch of the superior laryngeal nerve. Alright. At this point the rest of the fibers are going to be general visceral afferent
33:01
and efferent fibers going together to various organs, so parasympathetic and sensory fibres
33:08
go together. Around the heart, there’s gonna be a cardiac plexus, which is a mixed plexus
33:14
containing parasympathetic fibers from the vagus nerve and sympathetic fibres from the sympathetic trunk. The parasympathetic, as well as some sensory innervations from the
33:24
vagus nerve come in as the superior cervical, inferior cervical and thoracic cardiac branches.
33:32
While I did say that the nucleus ambiguous is a motor nucleus, research have shown that
33:37
most parasympathetic fibers coming in to the heart actually comes from the nucleus ambiguous,
33:42
and to lesser extent the posterior nucleus of vagus nerve, so even tho I’ve put it
33:47
here as though they come from the posterior nucleus of the vagus nerve, just keep in mind that most parasympathetic innervation to the heart come from the nucleus ambiguous, to
33:57
reduce its heart rate. Some variations also say that cardiac branches come from the recurrent
34:03
laryngeal nerve and not from the vagus nerve directly. Keep these things in mind.
34:08
There’s also going to be fibers forming the pulmonary plexus, called bronchial branches,
34:13
which innervates the bronchial tree and the visceral pleura. Now, the vagus nerve is going to continue down the esophagus and form the esophageal
34:23
plexus, and then penetrate the diaphragm through the esophageal hiatus, and then divide into
34:28
two trunks. The left vagus nerve will form the anterior vagal trunk, and the right vagus
34:34
nerve will become the posterior vagal trunk. And this is important because they innervate different structures. The anterior vagal trunk will give off the
34:42
anterior gastric branches for the stomach, and the hepatic branches for the liver and the lesser omentum. The posterior vagal trunk will give off the
34:52
posterior gastric branches, which form the gastric plexus together with the anterior gastric branches. And it’s going to give off the celiac branches,
35:01
which feed into the celiac plexus, also known as the solar plexus, which is a huge plexus
35:06
within the abdominal cavity that forms secondary plexuses that supply nearly all the abdominal
35:12
organs. So, the parasympathetic input of the celiac plexus comes from the vagus nerve.
35:18
The posterior vagal trunk is also going to give off a few fibres towards the liver to
35:23
innervate the liver and gallbladder, and a few fibres towards the kidneys. So that is the general scheme of the vagus nerve. Again keep in mind there are variations
35:33
according to what source you study from. Let’s now do the accessory nerve. So the accessory nerve is purely a motor nerve. It provides motor functions to the sternocleidomastoid
CN 11 Accessory Nerve
35:45
and the trapezius, and it goes together with the vagus nerve to innervate muscles in the
35:51
pharynx, larynx and soft palate. So it’s accessory to the vagus nerve.
35:56
We got two motor nuclei. Just like the glossopharyngeal and the vagus nerve, this nerve also has motor
36:02
fibres coming from the nucleus ambiguous, located in the medulla oblongata, It also has the spinal accessory nuclei, which are nuclei that lie in the spinal cord, in
36:13
the 6 upper segments of the spinal cord, lateral to the anterior horns of the grey matter.
36:18
The nucleus ambiguous give rise to the cranial root of the accessory nerve, while the spinal
36:23
accessory nucleus give rise to the spinal root of the accessory nerve. The cranial root
36:29
is going to go out from the brainstem through the retro-olivary groove, while the spinal root is going to go up, enter the cranium through foramen magnus, and fuse with the
36:40
cranial root of the accessory nerve, which then form the trunk of the accessory nerve.
36:45
The trunk of this nerve is then going to go through the jugular foramen, and split into an internal branch and an external branch. Remember the vagus nerve has the superior
36:56
and the inferior ganglion of the vagus nerve. The accessory nerve is going to feed some
37:01
motor fibers into the vagus nerve the level of the inferior ganglion, and then go together
37:06
with the pharyngeal branch to form the pharyngeal plexus, and innervate the muscles of the soft
37:12
palate except the tensor veli palatini, and muscles of the pharynx, except the stylopharyngeus.
37:17
And, in some variations the nerve might also go together with the recurrent laryngeal nerve,
37:23
to help innervate the intrinsic muscles of the larynx. The external branch is easy, it’s going to descend along the neck, grab some fibers
37:32
from the anterior ramus of C2, C3 and C4 from the cervical plexus, and then go innervate
37:38
the trapezius and the Sternocleidomastoideus. So that is the accessory nerve. Let’s now
CN 12 Hypoglossal Nerve
37:45
cover the hypoglossal nerve, the last of the 12 cranial nerve. The hypoglossal nerve is relatively easy. It is purely a motor nerve, responsible for
37:54
controlling the movement of the tongue. Which means that it plays a crucial role in tongue mobility and articulation, making it essential for speech and swallowing.
38:04
The hypoglossal nerve originates from the nucleus of the hypoglossal nerve, located within medulla oblongata. The nerve is going to give off somatic efferent fibers, or motor
38:15
fibers, that’re going to go out from the brainstem in the sulcus between the olive and pyramid, and then travels a short distance within the cranial cavity, and then exits
38:24
the skull through the hypoglossal canal. As the nerve is now outside the cranium, it travels
38:30
between the internal carotid artery and the internal jugular vein, to then form an arch
38:36
we call arch of the hypoglossal nerve. It then goes towards the tongue and give off
38:41
lingual branches to supply the muscles of the tongue, which primarily include the extrinsic muscles, you know the genioglossus, Styloglossus and hyoglossus. And the intrinsic muscles,
38:52
which are the superior and inferior longitudinal lingual muscles, and the vertical and transverse
38:57
muscles of the tongue. The hypoglossal nerve is closely related with the cervical plexus, in that the anterior ramus of the 1st and 2nd cervical spinal nerves
39:08
are going to send some motor fibres towards the hypoglossal nerve, that travels with the
39:13
hypoglossal nerve to supply the geniohyoid muscle. When you study the hypoglossal nerve,
39:20
you might find some variations that mention a meningeal branch, coming from the sensory spinal ganglion of C2, that also might run through the hypoglossal canal and help innervates
39:29
the dura mater in the floor of the posterior cranial fossa. The hypoglossal nerve will also send some motor fibres along the superior root of the
39:39
ansa cervicalis, that go together with the inferior root of ansa cervicalis, from the
39:44
C2 and C3, to form a nice loop called ansa cervicalis. So that is the general scheme
39:51
of this nerve and it’s associated branches. That’s it for this video, we went through all the schemes for each cranial nerve. I know it might be a lot to take in, but what
40:00
helped me to memorize them while studying the cranial nerves was to re-draw the schemes several times so that you involve some muscle memory along with cortical memory.
40:10
Thank you so much for watching another one of my videos. If you enjoyed, learned something from it, please remember to like, comment your favourite moment, subscribe. Turn on
40:17
those notifications. If you looking for other ways to support, go ahead and check out the link in the description box. Have fun ya’ll. Peace.
Cranial Nerves
Taim Talks Med
13 / 13
©Copyright 2025 for Taimtalksmed. Powered by Abdalrahman Atwah.
