8. Vestibular and Auditory Systems
VIII travels with VII en route to brainstem
Vestibular System
A.
Inner Ear
-
petrous portion of temporal bone
-
semicircular ducts
-
utricle (static+horizontal)
-
saccule (vertical motion)
-
epithelium
-
stereocilia
- deflection toward tallest cilia à depolarization
B.
CN VIII
C.
Clinical Correlations
i.
nystagmus
ii.
benign paroxysmal positional vertigo
iii.
labyrinthitis
iv.
Meniere’s disease
v.
vestibulotoxicity
vi.
schwannoma
Auditory System
A.
Outer Ear
B.
Middle Ear
bones:
malleus, incus, stapes
muscles:
tensor tympani, stapedius
a.
Clinical Correlations
i.
conductive hearing loss
ii.
otitis media
iii.
tympanic membrane perforation
iv.
meningitis
C.
Inner Ear
-
cochlea
-
oval window à scala vestibuli à scala tympani à oval window
-
high frequency à low frequency
-
scala media (filled with endolymphatic fluid)
- hair cells, tectorial
membrane
- single inner row of
hair cells (most important)
D.
CN VIII
E.
Clinical Correlations