Vestibular function Flashcards
What is the vestibular system?
A sensory system essential in the control of posture and balance
Vestibular apparatus comprises of…
3 semi circular canals
utricle
saccule
What are the swellings at the bottom of the semi circular canals called?
ampulla
What do the ampulla contain?
cristae made of cupula containing sensory hair cells
What are the otolith organs?
utricle and saccule
What do each of the vestibular apparatus detect?
SSC: rotational acceleration
utricle: horizontal - back/front tilt
saccule: vertical acceleration
What is cupula?
gelatinous material stretching across ampulla
What nerve do the ciliary hair cells synapse with?
CN 8 - vestibulocochlear nerve
Why does the endolymph not initially move?
inertia
Why does the ampulla move instantly?
embedded into skull
What happens if there is sudden stop in movement and the endolymph keeps moving?
dizziness and movement
What are the 2 types of cilia of hair cells?
kinocilium - single, large
stereocilia
Does distortion away or towards kinocilium result in APs firing?
towards kinocilium
Where does integration of sensory information happen?
cerebellum
What are maculae and what are the ways they are arranged?
sensory receptors in otolith organs
utricle: horizontal and saccule: vertical
What do the cilia protrude into in the otolith organs?
otolith membrane with calcium carbonate crystals (otolith) embedded
What is otolith?
CaCO3 crystals
Are otoliths or endolymph affected more by gravity and why?
otoliths - denser
What do the cerebellar centres co-ordinate?
postural muscles to maintain balance
Where do vestibular nuclei receive input from?
proprioceptors - neck, body position etc
What is kinaesthesia?
perception of movement and body position
What tracts to the vestibular system reflexes involve?
vestibulocortical and vestibulospinal
tonic labyrinthine reflexes
keep axis of head in constant relationship with body information
Dynamic righting reflexes
rapid postural adjustments - stop falling when you trip
long reflexes, extension of limbs
What animal is dynamic righting reflexes most apparent in?
cats
Vestibulo-occular reflexes
nystagmus and intortion/extortion
vestibular and visual apparatus and postural control
If there is right rotation which side of nystagmus would there be?
right and then change to left after it finishes
caloric stimulation: COWS
water - showing horizontal semi circular canals
cold opposite, warm same side - for nystagmus
What is nystagmus?
constant uncontrolled movements of the eyes
Kinetosis
motion sickness
Autonomic nervous system - motion sickness signs
pallor, sweating, decrease BP, nausea, vomiting, dizziness
Why does motion sickness happen?
vestibular and visual system inputs to cerebellum in conflict
Where do sickness symptoms for motion sickess go to?
hypothalamus
Labyrinthitis
infection interfering with vestibular function
ANS symptoms and vertigo
Vertigo
perception of movement in absence of movement
Meniere’s disease - what causes it?
overproduction of endolymph leading to increased pressure
tinnitus
subjective noise
Does tilting the head forward or backward bend towards the kinocilium and lead to depolarisation?
backwards
