vestibular system Flashcards
what are the 3 main inputs in the vestibular system
visual
proprioceptive
and vestibular information
what is the vestibular system
system that allows us to keep balance/ corporate balance e.g posture
what are the outputs of vestibular system
mainly reflexes to maintain stable posture and stable gaze
e.g ocular reflex and postural control
what is role of cns
integrates information and generates responses
where is vestibular organ found
posterior area in inner ear
contain hair cells
where are utricle and saccule located
in vestibule
are joined by conduit
saccule is also joined to cochlea
what are the 3 semicircular canals on each ear
anterior
posterior
lateral
semicircular canals have ampulla on one side and connected to utricle
why are the planes for the anterior and posterior canals important
determine which structure will be stimulated with specific head movement
what are vestibular hair cells called
kinocilium - biggest cilium
stereocilia - hairs on hair cells
what is role of cilia
allows cells to depolarise cell with movement of endolymph generated by head movements
what are the organs in vestibular system
3 semicircular canals and otoliths: utricle and saccule
why are utricle and saccule called otolith organs
contain otoliths(crystals)
cells are located on maculae
- placed horizontally in utricle
- placed vertically in saccule
what do the maculae contain
hair cells, gelatinous matrix and otoliths
what are otoliths
carbonate crystals that help deflection of hairs
what can be found in canals
hair cells located in ampulla
rest of canal has liquid high in potassium called endolymph
what do ampulla has
crista, where hair cells are located
cells are surrounded by cupula which help hair cell movement
what is orientation of canals in head
anterior and posterior canals form 90” angle
lateral canals are horizontal to other canals
where are primary afferents end
in vestibular nuclei and in cerebellum
where do vestibular nuclei have projections to
spinal cord - for postural movement
nuclei of extraocular muscle - for eye movement
cerebellum
centres for cardiovasc and resp control
what is the main processing centre for vestibular system
in parietal lobe - parieto- insular vestibular cortex
what are the vestibular system functions
- detect and inform about head movements
- keep images fixed in retina during head movements
- postural control
explain hair cell potentials
have resting potential - have basal discharge to nerve
hairs moving towards kinocilium generates depolarisation and increase in nerve discharge
hairs moving away - generates hyperpolarisation and reduction in nerve discharge
what movements is utricle sensitive to
horizontal
what movements is saccule sensitive to
vertical
how do circular canals work
angular acceleration
cupulla moves and displaces hair cells
output signal on 8th nerve is velocity
what is the vestibulo ocular reflex
keeps images fixed in retina
connections between vestibular nuclei and oculomotor nuclei
- eye movement is opposite direction to head movement, but same velocity and amplitude
what is the vestibulo spinal reflex
postural control - avoidance of falls and compensatory body movement according to head position
motor neurones to limb muscles - lateral tract
motor neurons to neck and back muscles - medial tract
how to carry out assessment of vestibular system
anamesis - history posture and gait cerebellar function eye movements vestibular tests ct,mri symptoms and impact assessment
what are some vestibular tests that can be carried out
caloric test
video head impulse test
vestibular evoked myogenic potential
rotational test
what is the main symptoms of balance disorder
dizziness and vertigo(spinning)
how can balance disorders be categorised
location of affected structure
evolution of signs and symptoms
what is a peripheral vestibular disorder
labyrinth and/or 8th nerve disorder
what are some examples of peripheral vestibular disorders
more common
vestibular neuritis
benign positional vertigo bppv
menieres disease
unilateral/bilateral vestibular hypofunction
what are central nerve disorders
anything involving brainstem and upwards
what are some examples of central vestibular disorders
stroke
ms
tumours
what is bppv
abnormal presence of otolith crystals in canals
what is menieres disease
affects both hearing and vestibular - problem with absorption of endolymph
what are acute balance disorders
vestibular neuritis
stroke
intermittent balance disorders
bppv
recurrent balance disorders
menieres disease
migraine
progressive balance disorders
schwanonnoma vestibular
degenerative conditions e.g ms
