Neuro-auditory+vestibular System Flashcards
what captures low frequency motion (movement )
vestibular organ
what captures high frequency motion (movement )- and where is it found
hearing organ (organ of corti)- in basilar membrane of scala media
what does the scala vestibuli and scala tympani contain and what is high in
perilymph - high in sodium
what does the scala media contain and what is it high in
endolymph - high in potassium
how is the basilar membrane organised
tonotopically-
base to capture high frequency- narrow and tight
apex= wide and loose for low frequency
what are the hairs of the hair cells called and
what is the longest cilium called
stereocilia
kinocilium- longest cilium
explain transduction in hearing- haircells
- Deflection of the stereocilia towards (kinocilium) opens K+ channels
- cell depolarises
(opening VG Ca2+ channels. calcium enter)
releasing NT (glutamate) to afferent nerve+ depolarises. - higher amplitude= greater stereocilia deflection + [K+] channel opening.
Causes of conductive hearing loss outer vs middle ear
outer- wax/FB
inner- otitis/otosclerosis
what is otitis
bubble can be seen through ear drum suggesting there is liquid inside middle ear
Causes of sensorineural hearing loss- inner
inner- noise, presbycusis, ototoxicity
nerve- acoustic neuroma (vestibular schwannoma) - unliteral
2 tests to do with tuning forks and what does it tests for
weber test and Rinne test
for gross hearing loss
audiometry/audiogram what is this and the ranges for
normal hearing
mild hearing loss
moderate hearing loss
severe hearing loss
profound hearing loss
hearing threshold plotted to define if there is hearing loss or not- (dB)
normal hearing=0-20
mild hearing loss 20-40
moderate hearing loss 40-70
severe hearing loss 70-90
profound hearing loss 90-120
what are OAE - otoacoustic emission
Low intensity sounds produced by normal cochlea
from Expansion and contraction of OHCs
Often tested in newborn hearing screening and as part of hearing loss monitoring
treatment for hearing loss
underlying cause
hearing aid
cochlear implants
brainstem implants
vestibular system- what are the input and outputs
input- movement and gravity
output - ocular reflex// postural control
what are otoliths for
carbonated crystals that helps deflection of hairs
what does the maculae contain
hair cells, gelatinous matrix and otoliths
what happens when hairs move away from kinocilium
hyperpolarisation and reduction in nerve discharge
inhibition
vestibular system functions- 3 examples
detects head movement
-keep image fixed in retina during head movement
-balance
what are the 2 vestibular reflexes
VOR= vestibulo-ocular reflex
VSR= vestibulo spinal reflex
what is the vestibulo-ocular reflex
-keeps image fixed in the retina
-connection between vestibular nuclei and oculomotor nuclei
-eye movement in opposite direction to head movement in same velocity and amplitude
symptoms seen in acute (usually unilateral) vs slow ONSET
acute- imbalance/nausea + VERTIGO
slow -imbalance/nausea
NO vertigo
balance disorders- location- peripheral (vestibular organ) vs central (CNS) causes
peripheral -BPPV (benign paroxysmal positional vertigo) /Meniere’s disease
central- stroke/MS/tumours
what are the red flags in vestibular disorders
-headache
-gait problem
-acute onset
-hearing loss
-symptoms 4 days+
balance disorders:
acute
intermittent
recurrent
progressive
acute- vestibular neuritis/stroke (HINTS exam)
intermittent- BPPV (Dix-Hallpike test)
recurrent-migraine/meniere’s disease
progressive - schwannoma vestibular (8th cranial nerve)/MS
what is the HINTS exam
differentiating between vestibular neuritis or stroke
Head Impulse test- horizontal rotational VOR
Nystagmus
Test of Skew deviation- vertical misalignment
what is the Dix-Hallpike test and what to do following it
for Benign paroxysmal positional vertigo
-epley manoeuvre
