vestibular system

Question 1

what are the 3 main contributors to orientation ?

Answer 1

vision

vestibular system

proprioception

Question 2

why can vision be ambiguous ?

Answer 2

requires vestibular system to help validate and confirm what is seen

Question 3

what is the vestibular system /characteristics ? (3)

Answer 3

continuous w the cochlea

vestibular nerve joins with auditory nerve

otolith organs detect tilt and linear acceleration

Question 4

what are the 3 ear canals that are filled with fluid ?

Answer 4

posterior

horizontal

anterior

Question 5

what are the hair cells called and their role ?

Answer 5

stereocilia

movement depolarise the receptors and increase firing rate of the afferent

Question 6

what is the pull-push action of left-right signals ?

Answer 6

rotation/acceleration is signalled by difference in firing rate between the 2 ears

Question 7

what happens if we lose an ear ?

Answer 7

creates strong sense of rotation

causes vertigo and dizziness

Question 8

what are the 2 otolith organs ?

Answer 8

utricle - horizontal

saccule - vertical

Question 9

what is the somato-gravic illusion?

Answer 9

otolith organs experience continuous tilt without vision to help

leads to pilots nose diving into the sea due to false illusion at nigh time

Question 10

what is a cupula and how does it work ?

Answer 10

forms a seal around the canal

fluid pushes against it when it moves in different directions

canal only responds to rotation

Question 11

what is special about the cupula ? (3)

Answer 11

neutrally buoyant

same density as endolymph fluid

doesn’t respond to changes in orientation

Question 12

what happens to the cupula post alcohol ingestion ?

Answer 12

cupula becomes lighter than surrounding fluid

rises when we lie down

sensation of spinning to the left

Question 13

what happens to the cupula post heavy water ingestion ?

Answer 13

cupular beomces heavier than endolymph fluid

sinks when we lie down

spinning sensation to the right

Question 14

what is the vestibular ocular reflex ? (4)

Answer 14

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

Question 15

what is caloric vestibular stimulation?

Answer 15

modulates firing rate of primary vestibular afferents

changes convection currents in ears to change and mimic head movement

Question 16

what happens when warm water is poured down the ear during caloric vestibular stimulation ? (4)

Answer 16

heats up canal

increases firing rate

causes convection current

mimics head turning to that ear

Question 17

what happens when cold water is poured into the ear during caloric vestibular stimulation ? (3)

Answer 17

cools the canal

decreases firing rate

convection current in opposite directions o warm water

Question 18

how does the vestibular system relate to comatose patients ?

Answer 18

reflex eye movements can indicate integrity of brain stem

can be used for outcome prediction

if reflex abolished - 92% likely to die - brain dead

Question 19

how does the fear of falling link to falling ?

Answer 19

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