Vestibular system - balance Flashcards
how are the semi circular canals aligned?
they are arranged at right angles to each other
at what part of the semi circular canals contains sensory hair cells?
the ampulla (bulge at the bottom)
at what part of the utricle and saccule contain sensory hair cells?
mecllae
describe the structure of the ampulla.
inside the ampulla is the christae
within the christae lies gelatinous structure called cupula
the cupula extends the whole width of the ampulla and responds to movement of the endolymph fluid
the cilia of the sensory hair cells are embedded into the capulla
what does the semicircular canals and the otolith organs detect?
semicircular canals detect rotational movement
utricle detects movement in the horizontal plane i.e. side to side, tilting forward and back
saccule detects movement in the vertical plane i.e. up and down
the clip of the hair cells which are embedded into the capula synapse onto what?
the vestibulococlear nerve
does sudden rotation of the head cause the endolymph or the ampulla to move?
sudden head rotation will cause the ampulla to move as its attached to the skull.
the endolymph won’t due to its inertia.
what are the 2 different types of cilia found on the sensory hair cells?
kinocillium
stereocilia
what is the difference between the 2 cilia types found on the sensory hair cells?
kinocillium - only 1 and is very large
stereocilia - smaller and more in number
does movement of cilia in the direction of the kinocilia results in hyperpolarisation or depolarisation?
depolarisation and increased firing of action potentials form the vestibular nerve
how is the brain able to determine movement in time and space?
it uses the pattern of firing an inhibition of action potentials received from the vestibular nerve to build a 3D image of the body position
firing of AP determine the way in which the cilia are directed (towards kinocilia or away from it). This indicates whether the ampulla has tilted to the left or right therefore ultimately we can wok out what way we are moving from these signals received.
when rotating, how does suddenly stopping cause nausea and the sensation that we are still moving?
after a few seconds of rotating the endolymph catches up with the ampulla
but if we suddenly stop, the ampulla stops but the endolymph continues to rotate
the endolymph continuing to rotate will give our brain false signals that we are still moving thus giving us the sensation the we are. the nausea is due to the mixed signals received
integration of the sensory information from the vestibular apparatus takes place where?
in the cerebellum
what is the gelatinous mass found within the maculae of the otolith organs?
otolith membrane
what is found embedded into the otolith and what part is it found embedded into?
otoliths which are calcium carbonate CaC03 crystals
they are embedded into the macula’s membrane
why is the maculae more affected by gravity compared to the ampulla?
the otoliths are of greater density than the endolymph
what causes an increase in firing of AP’s from the maculae?
otoliths moving in the direction to the kilocillium
will tilting the head forward or back cause hyperpolarisation and therefore decrease in AP’s and why?
tilting the head forward will decrease action potentials because this will cause the otoliths to move away from the kilocilium
what is the difference in the position of the maculae in the saccule compared to the utricle?
the saccule- maculae are vertically orientated
the utricle - maculae are horizontally orientated
what is responsible for providing information on the orientation of your head when you are lying down?
vertically orientated maculae found within the saccule
what effect does labyrinthitis have on the inner ear and what symptoms does it cause?
acute interference with normal vestibular function
all ANS symptoms + vertigo
what is the pathophysiology of meniere’s disease?
overproduction of endolymph causing increased pressure
what are the symptoms of menderes disease?
vertigo, nausea, nystagmus, tinnitus
the inner ear is sensitive to certain drugs such as?
streptomycin
if vestibular impairment is chronic can the person still balance ? why?
is vestibular impairement is chronic, it can be well compensated for by the visual system
they will use their vision for balance instead of the otolith organs.
learning circuits are set up in the cerebellum but if the person cannot see then they will lose their balance
what leads to nystagmus at rest?
lesions of the brainstem
what is the name of this reflex -
rapid postural adjustments that are made to stop you falling when you trip
dynamic righting reflex
what is the tonic labyrinthine reflex?
keep the axis of the head in the constant relationship with the rest of the body
what is the dynamic righting reflex?
rapid postural adjustments that are made to stop you falling over the you trip
what is the tonic labyrinthine reflex?
keep the axis of the head in constant relationship with th rest of the body
what are the 2 vestibulo-ocular reflexes?
static reflex
dynamic vestibular nystagmus
what is the static reflex?
when you tilt your head your eyes introit/extort in order to keep the image the right way up (to an extent)
what is the dynamic vestibular nystagmus reflex?
saccadic eye movements that rotate the eye against the direction of rotation so the original gaze is preserved
how do you determine the direction of nystagmus?
the direction of the flick back
how i nystagmus used to test vestibular function?
post-rotary nystagmus (Barany chair) caloric stimulation (initiating nystagmus with cold or hot water)
does hot or cold water cause the nystagmus to move towards the affected side?
cold water = opposite side
warm water = same side
what is kinetosis and what is it due to?
motion sickness
due to maintained stimulation of the vestibular system which causes conflicted signals in the cerebellum
