Cranial Nerves Flashcards
What are the 12 cranial nerves ?
The 12 paired cranial nerves are:
I – Olfactory nerves
II – Optic nerves
III – Oculomotor nerves
IV – Trochlear nerves
V – Trigeminal nerves
VI – Abducens/abducent nerves
VII – Facial nerves
VIII – Vestibulocochlear nerves
IX – Glossopharyngeal nerves
X – Vagus nerves
XI – Accessory nerves
XII – Hypoglossal nerves
Large sulcus separating two lobes
longitudinal fissure ?
Cranial Nerve - 1
What does is it role ?
Where does it pass through ?
Olfactory
Sensory
Senses smell
It passes through the cribriform plate of the skull
Cranial Nerve - 2
What is its role ?
Where does it pass through?
Optic
Sensory
Transmission form the retina to the brain.
Everything from the right goes to the left, everything from the left goes to the right. This then goes to the thalamus and then the occipital lobe.
It passes through the optic canal of the skull.
Cranial Nerve - 3
Oculomotor
Motor
Innervates - Extraocular muscles (Muscles on the outside of the eye that act on the eye). These include:
- Superior rectus
- Medial rectus
- Inferior rectus
- Inferior oblique
Thanks to this nerve, we can direct our GAZE: superiorly, inferiorly, medially.
It also innervated the levator palpebral superiors, which means we can lift the eyelid.
It also allows for constriction and accommodation of the pupil. Does this by working with the optic nerve?
Enters through the superior orbital fissure.
Cranial Nerve - 4
Exit from skill?
Trochlear
Motor (Moves the eye)
Functions - Innervated the superior oblique muscle. It assists in depressing and abducting the eye and medially rotating the eye.
Exit from the skull via superior orbital fissure.
Cranial Nerve - 5
What three things is it split into?
Trigeminal
Largest Cranial Nerve
It has three divisions (ophthalmic, maxillary and mandibular).
Mixed (All three have a sensory component only V3 has a motor part). If you clench your teeth you can feel these muscles.
Motor Function - Innervated muscles of mastication (Chewing)
V3 - taste
Exit from skull?
Cranial Nerve - 6
Abducens
Motor
Innervates the lateral rectus muscle (Extra-ocular muscle)
Exists via superior orbital fissure.
Cranial Nerve - 7
Nerve name?
Sensory, Motor, or Mixed?
Functions?
Exit from the skull?
Facial
Mixed
Motor - Expression and salivary gland stimulation.
Runs through the parotid gland and branches into 5
exits through the stylomastoid foramen.
+ close eye, blow out cheek etc to test.
UPPER SPARES UPPER.
Cranial Nerve - 8
Nerve name?
Sensory, Motor, or Mixed?
Functions?
Exit from skill?
Vestibulocochlear nerve
Hearing and Balance.
SENSORY
2 branches
Vestiubo balance - Get someone to walk heel to toe; they will lose their balance if they are close !! REMEMBER TO STAY CLOSE TO THE PATIENT.
Cochlear Hearing - has sensory receptors (hair cells) in the inner ear. Whisper in one ear or rub fingers. Make sure to occlude the other ear tho as you can hear out of both ears.
Cranial Nerve - 9
Glossopharyngeal
MIXED
Motor - Parotid gland
Gag reflex - afferent.
If Uvula moves on saying “ahh” but not on gag = isolated 9th nerve palsy.
Cranial nerve 10
Vagus
Muscles of palate, pharynx, and layrnx.
Cranial nerve 11
Accessory
Motor
Innervates sternoclidomastour and trapezium
Movement of the neck and shoulder.
Exists jugular foramen
Cranial nerve 12
Hypoglossal
Motor
nnervates tongue muscles except for palatoglossus
Exits Hypoglossal canal
Which cranial nerves eyes look at eye movements ?
3, 4 and 6
How does the optic nerve and oculomotor nerve work together ?
They work together to complete the
- Pupillary light reflex and the accommodation reflex.
The optic nerve serves as the sensory or afferent pathway (towards the brain) and the oculomotor serves as the motor or efferent pathway (away from the brain)
The pupillary light reflex is a reflex that controls the diameter of the pupil in response to light.
When light enters either retina, it is sensed by the optic nerve, travels to the optic chiasm then to the optic tract.
The optic tract then sends a signal to a nucleus located in the midbrain called the pretectal nucleus.
This nucleus then sends signals to both the right and left Edinger-Westphal nuclei located in the midbrain, and those signals travel along preganglionic parasympathetic fibers that exit with the oculomotor nerve and synapse with postganglionic parasympathetic neurons in the ciliary ganglion.
Postganglionic nerve fibers leave the ciliary ganglion via short ciliary nerves to innervate the ciliary sphincter pupillae muscle of the iris to cause constriction.
Therefore, shining a light in one eye should cause a reflexive constriction of that same pupil called the direct pupillary light reflex, in addition to causing constriction of the contralateral pupil called the consensual pupillary light reflex.
This pupillary reflex is meant to constrict the pupil when there’s plenty of light, so as to prevent more light from reaching the retina, and the strength of this reflex is dependent on the intensity of the light shining into the eye.
The accommodation reflex, on the other hand, refers to the change in the shape of the lens of the eye in response to focusing on an object near or far away, similar to how a photographer changes their lens to take pictures on their camera.
Like the pupillary reflex, the accommodation reflex has a sensory, or afferent limb represented by the optic nerve, and a motor. or efferent limb represented by the oculomotor nerve.
Now, this pathway starts with light hitting the retina sending signals through the optic nerve, the optic chiasm, the optic tract, the lateral geniculate body, the optic radiation, and the visual cortex.
After this long and winding road, signals are sent through the efferent limb of the pathway.
First, they reach the superior colliculus in the midbrain, then the Edinger-Westphal nucleus which sends signals to both the right and left oculomotor nerves and the parasympathetic nerve fibers that travel with the oculomotor nerve.
The parasympathetic fibers synapse in the ciliary ganglion then send ciliary nerves to the sphincter pupillae to contract the pupil, and to the ciliary body which causes a sphincter like contraction around the lens which reduces tension and relaxes the lens, causing it to become thicker and more rounded.
So, overall, during accommodation on objects close to our face our pupils constrict, and our lens becomes thicker and more rounded, and when focusing on objects far away, our pupils dilate and our lens is thinner, because it’s under more tension..
