27. CN - VII/VIII Flashcards
CN VII
Name, Skull Exit, Branches and Paths, Distribution, Primordium
Facial Nerve
Exits Internal Acoustic Meatus of Petrous part of temporal bone
1. Greater Petrosal (via groove of greater petrosal) - over foramen lacerum, picks up symps from carotid - nerve of pterygoid canal - pterygopalatine GANGLION in PPF - V2 parasymps (hits lacrimal gland via V1!)
2. Chorda Tympani (out petrotympanic fissure) - submandibular ganglion - lingual nerve - taste and parasymps for V3 (submandibular/sublingual glands)
3. Facial Nerve Proper (out stylomastoid foramen) - branchiomotor to superficial face muscles of facial expression
Distribution: geographic territories radiating from parotid - temporal, zygomatic, mandibular, cervical nerves
Primordium: CN7 from Arch 2; Pretrematic is chorda tympani
What is Bell’s Palsy? Difference from upper and lower motor neuron lesion?
What is the nervus intermedius and what fibers does it carry?
Bell’s Palsy: often from HSV, dysfx CN7 - expressionless side of face (no buccinator, orbicularis oculi - cant close eye or keep food n mouth) - may affect taste/lacrimal gland
Upper motor neuron lesion = some movement of frontalis muscle preserved due to crossover
Lower motor neuron lesion = complete hemi-facial paralysis (no crossover downstream)
Nervus intermedius - smaller root of CN7 - only contains taste/parasymps below the larger branchiomotor root
CN VIII
Name, Skull Exit, Branches, Primordium
Vestibulocochlear Nerve
Exits skull through internal acoustic meatus of petrous temporal (shortest CN!)
1. Cochlear N. - to cochlea (hearing)
2. Vestibular N. - to semicircular canals (balance/motion)
Primordium: Otic Placode (Otocyst)
How are electrical nerve impulses generated in the saccule, utricle, semicircular canals, and cochlea of the inner ear?
Hair cells bend:
Saccule/Utricle - otoliths bend hair cells
Semicircular Canal - endolymph inertia bends hair cells
Cochlea - perilymph waves move membrane bends hair cells
Hair cell bending = opens K channels = K influx = activates K/Ca exchanger = Ca influx = release of NT vesicles = nerve impulse
