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The Cranial Nerves
1- Olfactory Nerve
Component:  Sensory Nerve

Course/Pathway:

It arise from the olfactory sensory receptor which is located at the mucous
membrane of nose above superior conchae
...

Then enter olfactory bulb and then enter to synapses in the nasal cortex area in
temporal lobe of cerebral cortex
...
It may be caused by tumor, Stroke,
Fracture of skull
...

It converges on optic disc & exit from the eye
...

The unit with the opposite side of optic nerve to form optic chiasma at the floor
of third ventricle and continue as optic tract
...

Some fibers synapse at superior colliculus of midbrain
...


Functions:

The optic nerve is also responsible for the light reflex and the accommodation reflex
...


Clinical Problems:           
Night Blindness
Color Blindness
Eyesight Problems

Causes:

Optic Neuritis
Tumor

3- Oculomotor Nerve

Component:   Motor Nerve

Origin:

Main Motor Nucleus:
It is situated in the Anterior part of Grey Matter that surrounds the cerebral
aqueduct of the Midbrain
...

It recieves corticonuclearfibers from both cerebral hemispheres
...
 
Through this routes, recieves information from visual cortex
...

These fibers synapse in the ciliary ganglion and supply Ciliary Muscles
...

It passes forward between the Posterior Cerebral and the superior cerebellar
artieries
...


Superior Ramus:

It supply the extra-occular muscles
...


Functions:

              It allows movement of the eye muscles, constriction of the pupil, focusing the eyes and the
position of the upper eyelid
...

When object is displaced near to far then Pupil Dilate
...

Incomplete lesions of Oculomotor nerve are common and may spare the
extra-occular muscles
...



4- Trochlear Nerve
Component:   Motor Nerve

Origin:

Trochlear Nerve Nucleus:

                                      It is situated in the Anterior part of the gray matter that surrounds the
cerebral aqueduct of the midbrain just inferior to oculomotor nerve
...

It immediately decussate with the nerve of the opposite side
...

Then enters the orbit through the superior orbital fissure
...


Functions:

           It enables movement in the eye's superior oblique muscle
...



    

  5-

Trigeminal Nerve

Component:   Mixed Nerve

Trigeminal Nerve Nuclei:

1
...
Spinal Nucleus
3
...
Motor Nucleus 

Main Sensory Nucleus:

Location:

           It lies in the Posterior part of the pons, lateral to the Motor Nucleus
...



Spinal Nucleus:

Location:

           It continues superiorly with the main Sensory Nucleus in pons and extend
inferiorly to the medulla oblongata and spinal cord upto the C2 segment
...

Mesencephalic Nucleus:

Location:

           It is located in the lateral part of the gray matter around the cerebral
aqueduct and extends to pons
...

Motor Nucleus:

location:

        It is located at the pons medical to Main Sensory Nucleus
...

Muscles of Mastication:
Mylohyoid


Digastric
Tensor Tympani 

Origin/Pathway:
Sensory Component:

                    Sensory fibers of pain, temperature, pressure goes to the trigeminal
ganglion from face and from the larger root
...

It also recieves fibers from the reticular formation
...

 Now the trigeminal nerve leaves the anterior aspect of the pons as a small
motor root & large sensory root
...

> It divides into three Nerves
...



Branches:

A-  Ophthalamic Nerve:

It is purely sensory nerve
...


Sub-branches:
1
...
Lacrimal Nerve: (recieve sensation from eye)

3
...

It leaves the skull through foramen rotundum
...
Infraorbital: (receive the sensation from the lower part of orbital cavity)
...
Supraorbital: (receive the sensation from the upper part of mouth/face)
...

Its opening the skull from foramen ovale
...
Muscular Branches: (Motor Branch)
...

2
...
            It supplies the lower part of skin
area        over chin and lower part of face
...
Lingual Nerve:                                                     It supplies the tongue
...


Motor Components:                                              Examine the teeth, jaws,
clavicle movement
...


Pain is felt most commonly over the skin areas innervated by the mandibular and
maxillary divisions of the trigeminal nerve, only rarely is pain felt in the area supplied
by tha Ophthalamic division
...

It receives corticonuclear fibers from both cerebral aqueduct
...

It recieves fibers from the visual cortex
...

Then emerges in the groove b/w the lower border of the pons and the medulla
oblongata
...

The nerve then enter the orbit through the superior orbital fissure & enter the
orbital cavity
...



Pathology:

               In a lesion of the abducens nerve, the patient cannot turn the eye laterally
...

Treatment:
1
...
Surgery

7- Facial Nerve
Component:  Mixed Nerve

Facial Nerve Nuclei:

1
...
The Parasympathetic Nucleus
3
...
 
It recieves corticonuclear fiber from opposite cerebral hemisphere for lower
part of face
...

i
...
Lacrimal Nucleus: (recieves fibers from hypothalamus concerned with

emotions, tear)
...

It concerned with the taste sensation
...

It synapse to the geniculate ganglion
...

Pathway:

It consist of sensory and motor roots
The fibers of the motor root first travel posteriorly around the medial side of the
abducens nerve
...

The two root of facial nerve emerges b/w pons & medulla
...

At the bottom of meatus, the nerve enter into facial canal in the inner ear
...


Facial Nerve Distribution:

At the level of facial canal:

i
...
Chorda Tympani Nerve:

              (Supply chorda Tympani muscle)

iii
...
Post Auricle Nerve:

             (Supply post occipital muscle)
ii
...
Stylohyoid Nerve:

             (Supply Stylohyoid muscle)

        Terminal Branches:

A
...
Zygomatic:

          (Supply Orbicularis occuli, Zygomaticas)

C
...
Marginal:

         (Supply Mentalis)
E
...
Vestibular means balance

β
...
(position of
head)
The nerve also conducts impulses from semicircular canals
...

The nerve passes through pons & medulla
...

Then divided into two fibers
...


=Other fibers is descend into vestibulospinal tract
...


Clinical Problems:

          Damage to vestibular nerve results in

    Vertigo, Dizziness, Nystagmus
...
Rotational test
2
...
Electronystagmography

Treatment:

       Physiotherapy 

Cochlear Nerve

Pathway:


The cochlear nerve conducts nerve impulses from the organ of Corti in the
cochlea
...

On entering the pons, the nerve fibers divide into two
...


Functions:

          The cochlear nerve is responsible for hearing
...

Examination Test:
1
...
Weber's Test

Course of Vestibulocochlear Nerve:

The vestibular and cochlear part of the nerve leaves the anterior surface of the
brain b/w the pons & the medulla oblongata
...

The fibers are then distributed to the different parts of the internal ear
...
Main Motor Nucleus
2
...
Main Sensory Nucleus

Main Motor Nucleus:

     It lies deep in the reticular formation of medulla oblongata
...


•It recieves afferent fibers from hypothalamus
...

Main Sensory Nucleus:

•It is the part of the Nucleus of the tractus solitarius
...

Pathway/course:

The glossopharyngeal nerve leaves the anterolateral surface of the medulla
oblongata
...


It passes laterally in the Posterior cranial fossa and leaves the skull through the
jugular foramen
...

To reach the border of stylopharyngeus muscles
...


Sensory Component: goes to the palate & tongue
...

Sensory fibers innervate the Posterior third of the tongue for general sensation
& taste
...

Examination Test:

           The nerve can be tested by checking a person's gag reflex and doing a taste
test on the posterior third of the tongue
...


Vagus Nerve Nuclei:

1
...
The Parasympathetic Nucleus 
3
...

It recieves corticonuclear fibers from the cerebral hemispheres
...


Functions: 

 Pharynx: Swallowing 

 Larynx: Voice production
Parasympathetic Nucleus:

It is located at the floor of the 4th ventricle
...

It recieves efferent fibers to the bronchi, lungs, heart, trachea, esophagus,
stomach and intestines
...

It takes sensation from posterior 1/3 of tongue
...


Course/Pathway:

The vagus nerve leaves the anterolateral surface of the medulla oblongata
Then enters in a groove b/w the olive & the inferior cerebellar peduncle
...

Then they divided into two sensory ganglion
...


Inferior Ganglion: below the jugular foramen
...

The nerve descends in the neck within the carotid sheath with the internal
jugul

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