Vestibular Function Flashcards
where is the vestibular system
in the inner ear
the vestibular system has how many semi-circular canals
3
what do the semi-circular canals attaach to
the utricle
describe the relation of the semi-circular canals to each other
they are all at right angles with one another so they can detect motion in 3 directions
the swelling at the base of the semi-circular canal is called the …
ampulla
which parts of the vestibular system contain sensory hair cells
ampulla, utricle and saccule
what are the otolith organs
utricle and saccule
what is detected by the semi-circular canals
rotational acceleration
what is detected by the utricle and saccule
linear acceleration
utricle: back to front
saccule: vertical
fluid of semi-circular canals
endolymph
structure of cristae
a cupula in endolymph which has cilia embedded in it
how does the crista detect movement
rotation of the head creates inertia which moves the endolymph bending the cupula and the cilia within it in the opposite direction of movement.
sterocilia move in the direction of the kinocilium causing depolarisation and APs sent to the vestibular nerve
two types of cilia in hair cells
stereocilia and kinocilium
what happens when stereocilia distort away from the kinocilium
hyperpolarisation and decreased in APs to vestibular nerve. tell brain they’re travelling in other direction
origin of vestibulocochlear nerve
pons
what happens when travelling in a direction at a constant velocity
there is no shearing force on the cilia so no APs sent
what happens when you stop rotation
there is shearing of the cupula in the opposite direction
sensory apparatus of utricle and saccule
maculae
which direction are the maculae of the saccule orientated
on the vertical plane
structure of maculae
cilia (one kinocilium and many stereocilium) protuding into a gelatinous mass of the otolith membrane. Otoliths (crystals of CaCO3) are embedded in the membrane
crystals of what substance are embedded in the otolith membrane
CaCO3
why are otoliths more affected by gravity than endolymph
because they are denser, heavier
process of otolith organs detecting movement
head tilts –> otoliths follow direction –> distort jelly –> move cilia –> discharge of APs
tilting the head back increases/decreases the number of APs sent
increases - moves cilia towards the kinocilium
tilting the head forwards increases/decreases the number of APs sent
decreases
which organ detects head movement tilting back and forth
utricle
where is the vestibular nuclei
in the medulla
how does info from the vestibular nerve reach the cortex
vestibular nerve –> vestibular nuclei –> thalamus –> cortex
true/false the vestibular nuclei recieves information from up and down an also sends information up and down
true
what reflex keep the head in the axis with the body
tonic labrinthine reflex (maculae and neck proprioceptors)
what reflex makes rapid postural adjustments when falling/tripping
dynamic righting reflexes
why is balancing harder when you close your eyes
because the visual system send descending projections which control posture
true/false people with damaged vestibular apparatus can still maintain good balance
true - if the movement is slow and the eyes are open. NOT is eyes are CLOSED
what is the static reflex
when you tilt your head and your eyes intort/extort to compensate so the image stays right way up
what is nystagmus
involuntary eye movement
right nystagmus happens when you rotate _____
right (direction of flick back)
when your head rotates right which way should your eyes rotate in the orbit
left
what happens in dynamic vestibular nystagmus
the head rotates in a direction and the eyes compensate to stay orientated on the same spot until they reach their limit and flick back
what happens in caloric stimulation
one ear warm; one ear cold. endolymph is affection by convection
nystagmus occurs in direction of warm ear
complications of caloric stimulation nystagmus
nausea and vomiting
motion sickness happens when which two systems are in conflict
visual and vestibular
what is overproduced in meniere’s disease
endolymph
presentation of meniere’s
vertigo, nausea, nystagmus, tinnitus
what is vertigo
feeling of movement when you’re still
true/false brainstem lesions can cause nystagmus
true
