vestibular system Flashcards
what are the 3 main contributors to orientation ?
vision
vestibular system
proprioception
why can vision be ambiguous ?
requires vestibular system to help validate and confirm what is seen
what is the vestibular system /characteristics ? (3)
continuous w the cochlea
vestibular nerve joins with auditory nerve
otolith organs detect tilt and linear acceleration
what are the 3 ear canals that are filled with fluid ?
posterior
horizontal
anterior
what are the hair cells called and their role ?
stereocilia
movement depolarise the receptors and increase firing rate of the afferent
what is the pull-push action of left-right signals ?
rotation/acceleration is signalled by difference in firing rate between the 2 ears
what happens if we lose an ear ?
creates strong sense of rotation
causes vertigo and dizziness
what are the 2 otolith organs ?
utricle - horizontal
saccule - vertical
what is the somato-gravic illusion?
otolith organs experience continuous tilt without vision to help
leads to pilots nose diving into the sea due to false illusion at nigh time
what is a cupula and how does it work ?
forms a seal around the canal
fluid pushes against it when it moves in different directions
canal only responds to rotation
what is special about the cupula ? (3)
neutrally buoyant
same density as endolymph fluid
doesn’t respond to changes in orientation
what happens to the cupula post alcohol ingestion ?
cupula becomes lighter than surrounding fluid
rises when we lie down
sensation of spinning to the left
what happens to the cupula post heavy water ingestion ?
cupular beomces heavier than endolymph fluid
sinks when we lie down
spinning sensation to the right
what is the vestibular ocular reflex ? (4)
stabilisation of gaze with input form both sides of head
canals operate in push-pull manner
head rotation causes excitation and inhibition on diff sides
asymmetry indicate rotation
what is caloric vestibular stimulation?
modulates firing rate of primary vestibular afferents
changes convection currents in ears to change and mimic head movement
what happens when warm water is poured down the ear during caloric vestibular stimulation ? (4)
heats up canal
increases firing rate
causes convection current
mimics head turning to that ear
what happens when cold water is poured into the ear during caloric vestibular stimulation ? (3)
cools the canal
decreases firing rate
convection current in opposite directions o warm water
how does the vestibular system relate to comatose patients ?
reflex eye movements can indicate integrity of brain stem
can be used for outcome prediction
if reflex abolished - 92% likely to die - brain dead
how does the fear of falling link to falling ?
when at height we sway less
when we sway it activates our systems
without system activation it can increase changes of falling due to limited reflexes
