Lecture 2: Cranial Nerves Flashcards
What are the four parasympathetic ganglion?
Cilliary
Pterygopalatine
Otic
Submandibular
Cranial Nerve I
What is this nerve?
What is its CNS origin?
What is its distribution?
Olfactory Nerve
Telencephalon
Olfactory mucosa of nose
Where is CN I located?
Where does it synapse onto?
Olfactory organ through cribiform plate to synapse onto Olfactory bulb
What is the function of CN I?
What happens if this nerve is damaged?
Special Sensory: smell/olfaction
If damaged, can cause anosmia
Cranial Nerve II
What is this nerve?
What is its CNS origin?
What is its distribution?
Optic Nerve
Diencephalon
Retina of eye
What is the general tract of CNII from the brain?
- Optic nerve fibers arise from ganglion cells in retina
- Enters cranium via optic foramen
- Nerves unite at optic chiasm
- Synapse onto lateral geniculate bodies of thalamus
What is the function of CN II?
What happens if this nerve is damaged?
Special Sensory: vision
If damaged, can cause anopsia (visual defects)
What cranial nerves go through the superior orbital fissure?
CN III, IV, V1, VI
Cranial Nerve III
What is this nerve?
What is its CNS origin?
Oculomotor Nerve
Midbrain/Mesencephalon: Oculumotor and Edinger Westphal nuclei
What is the general tract of CN III from the brain?
- Exits midbrain through dura lateral to diaphragma sellae
- Runs in lateral wall of cavernous sinus
- Enters through superior orbital fissure into orbit
What is the parasympathetic motor function of CN III?
(What muscles is it innervating?)
Visceral Motor Functions
- Innervates sphincter pupillae muscle (constrictor)
- Contracts cilliary muscle to make muscle more round and relaxed (good with near vision)
What is the sympathetic motor function of CN III?
(What muscles is it innervating?)
Somatic Motor Functions
- Innervates intrinsic eye muscle: Elevates eyelid
- Levator Palpebrae Superioris Muscle
- Innervates extrinsic eye muscle: Move eyeball
- Superior Rectus Muscle
- Medial Rectus Muscle
- Inferior Rectus Muscle
- Inferior Oblique Muscle
What happens if CN III is damaged?
- Ptosis (upper eleyid droop)
- Paralysis of eye muscles leading to strabismus
- eyes are not parallel and deviated properly
- Diplopia (double vision)
- Difficulty with focus
- Dilated pupil
Gaze will be down and out!!
What presents first if CN III is compressed by an aneurysm?
Problems with parasympathetic division
Horner’s syndrome symptoms
Cranial Nerve IV
What is this nerve?
What is its CNS origin?
Trochlear Nerve
Midbrain: Pontine (Abducens) Nucleus
What is the general tract of CN IV?
- Exit dorsal surface of midbrain and pierce dura mater at margin of entorium cerebelli
- Run in lateral wall of cavernous sinus
- Enters orbit via superior orbital fissure
What is the only nerve that exits on the dorsal surface of the brainstem?
Trochlear Nerve (CN IV)
What is the function of CN IV?
What happens if this nerve is damaged?
Somatic Motor: Innervates Superior Oblique Muscle (depresses, internally rotates, and abducts the eye)
If damaged, can lead to limited downard movement of eye, strabismus, and diplopia
Cranial Nerve VI
What is this nerve?
What is its CNS origin?
Abducens Nerve
Pontine Medullary Junction
What is the general tract of CN VI?
- Emerge from brainstem at pontine-medullary junction
- Traverse pontine cistern and pierce dura covering the clivus
- Run in cavernous sinus near Internal Carotid A.
- Enters orbit via superior orbital fissure
What is the function of CN VI?
What happens if this nerve is damaged?
Somatic Motor: Lateral Rectus Muscle (abducts eye)
If damaged, can lead to paralysis of lateral eye movements and diplopia
Cranial Nerve V
What is this nerve?
What is its CNS origin?
Trigeminal Nerve
Pons
Derivatives of 1st pharyngeal arch
What are the divisions of CN V?
CN V1: Ophthalmic Branch of the Trigeminal Nerve
CN V2: Maxillary Branch of the Trigeminal Nerve
CN V3: Mandibular Branch of the Trigeminal Nerve