Lecture 2: Cranial Nerves Flashcards
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
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 CN X?
- Emerges from medulla
- Exit cranium through jugular foramen
Cranial Nerve IV
What is this nerve?
What is its CNS origin?
Trochlear Nerve
Midbrain: Pontine (Abducens) Nucleus
What presents first if CN III is compressed by an aneurysm?
Problems with parasympathetic division
Horner’s syndrome symptoms
What is the general tract of CN VII?
- Emerges from the pontine-medullary jxn
- Cross posterior cranial fossa to exit skull via internal acoustic meatus
- Run in facial canal and exit via stylomastoid foramen
- Pass through the parotid gland
What opening does the CN V2 exit from?
Foramen rotundum
What CN is affected in Bell’s Palsy?
What occurs as a result?
CN VII
Inability to use facial muscles
Cranial Nerve I
What is this nerve?
What is its CNS origin?
What is its distribution?
Olfactory Nerve
Telencephalon
Olfactory mucosa of nose
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 is the general tract of CN XII?
- Emerges from the medulla
- Exits skull via hypoglossal canal
- Travels with cervical plexus
- Cross occipital A.
- Enter oral cavity
What is the function of CN V2?
Sensory Afferent
Skin of face, lower eyelid, cheek, upper lip, maxillary teeth, mucosa of nose, maxillary sinus
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
What is the function of CN XII?
What happens if this nerve is damaged?
Somatic Efferent: Supplies all intrinsic and extrensic muscles of the tongue except Palaoglossus Muscle.
If damaged, can lead to difficulty swallowing and speaking.
Cranial Nerve III
What is this nerve?
What is its CNS origin?
Oculomotor Nerve
Midbrain/Mesencephalon: Oculumotor and Edinger Westphal nuclei
Cranial Nerve IX
What is this nerve?
What is its CNS origin?
Glossopharyngeal Nerve
Medulla
Derivatives of 3rd pharyngeal arch
What is the function of CN I?
What happens if this nerve is damaged?
Special Sensory: smell/olfaction
If damaged, can cause anosmia
Simply put, where are the 12 cranial nerves located?
Use Rule of 4s
Cranial Nerves 1-4 are above the pons
Cranial Nerves 5-8 in the pons
Cranial Nerves 9-12 in the medulla
What is the function of CN VII?
Special Visceral Efferent (Branchial Motor)
- Innervates Stapedius muscle (in ear)
- Innervates Stylohyoid, Posterior belly of Digastric Muscle
- Innervates muscles of facial expression
General Visceral Efferent
- Innervates lacrimal, submandibular, and sublingual glands
- Innervates mucous membrane of nose
- Innervates hard and soft palates
General Sensory Afferent
- Skin of concha of auricle, small patch behind ear
- Helps CN V3 with acoutsti meatus and external tympanic membrane
Special Sensory Afferent
- Senses taste from anterior ⅔ of tongue
- CN V3 does sensation!
- Senses taste from hard and soft palates
What is the function of CN VIII?
What happens if this nerve is damaged?
Special Sensory:
- Cochlea: Auditory Information
- Semicircular Canals: Balance Information
If there is damage, can lead to loss balance, nausea, vomitting, dizziness, and deafness
What direction will the tongue deviate if there is a lesion of the hypoglossal nerve on one side?
Towards the lesion
May atrophy
Cranial Nerve V
What is this nerve?
What is its CNS origin?
Trigeminal Nerve
Pons
Derivatives of 1st pharyngeal arch
Cranial Nerve VIII
What is this nerve?
What is its CNS origin?
What is its distribution?
Vestibulocochlear Nerve
Pontine Medullary Junction
Internal ear