Vestibular system - balance

Question 1

how are the semi circular canals aligned?

Answer 1

they are arranged at right angles to each other

Question 2

at what part of the semi circular canals contains sensory hair cells?

Answer 2

the ampulla (bulge at the bottom)

Question 3

at what part of the utricle and saccule contain sensory hair cells?

Answer 3

mecllae

Question 4

describe the structure of the ampulla.

Answer 4

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

Question 5

what does the semicircular canals and the otolith organs detect?

Answer 5

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

Question 6

the clip of the hair cells which are embedded into the capula synapse onto what?

Answer 6

the vestibulococlear nerve

Question 7

does sudden rotation of the head cause the endolymph or the ampulla to move?

Answer 7

sudden head rotation will cause the ampulla to move as its attached to the skull.
the endolymph won’t due to its inertia.

Question 8

what are the 2 different types of cilia found on the sensory hair cells?

Answer 8

kinocillium

stereocilia

Question 9

what is the difference between the 2 cilia types found on the sensory hair cells?

Answer 9

kinocillium - only 1 and is very large

stereocilia - smaller and more in number

Question 10

does movement of cilia in the direction of the kinocilia results in hyperpolarisation or depolarisation?

Answer 10

depolarisation and increased firing of action potentials form the vestibular nerve

Question 11

how is the brain able to determine movement in time and space?

Answer 11

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.

Question 12

when rotating, how does suddenly stopping cause nausea and the sensation that we are still moving?

Answer 12

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

Question 13

integration of the sensory information from the vestibular apparatus takes place where?

Answer 13

in the cerebellum

Question 14

what is the gelatinous mass found within the maculae of the otolith organs?

Answer 14

otolith membrane

Question 15

what is found embedded into the otolith and what part is it found embedded into?

Answer 15

otoliths which are calcium carbonate CaC03 crystals

they are embedded into the macula’s membrane

Question 16

why is the maculae more affected by gravity compared to the ampulla?

Answer 16

the otoliths are of greater density than the endolymph

Question 17

what causes an increase in firing of AP’s from the maculae?

Answer 17

otoliths moving in the direction to the kilocillium

Question 18

will tilting the head forward or back cause hyperpolarisation and therefore decrease in AP’s and why?

Answer 18

tilting the head forward will decrease action potentials because this will cause the otoliths to move away from the kilocilium

Question 19

what is the difference in the position of the maculae in the saccule compared to the utricle?

Answer 19

the saccule- maculae are vertically orientated

the utricle - maculae are horizontally orientated

Question 20

what is responsible for providing information on the orientation of your head when you are lying down?

Answer 20

vertically orientated maculae found within the saccule

Question 21

what effect does labyrinthitis have on the inner ear and what symptoms does it cause?

Answer 21

acute interference with normal vestibular function

all ANS symptoms + vertigo

Question 22

what is the pathophysiology of meniere’s disease?

Answer 22

overproduction of endolymph causing increased pressure

Question 23

what are the symptoms of menderes disease?

Answer 23

vertigo, nausea, nystagmus, tinnitus

Question 24

the inner ear is sensitive to certain drugs such as?

Answer 24

streptomycin

Question 25

if vestibular impairment is chronic can the person still balance ? why?

Answer 25

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

Question 26

what leads to nystagmus at rest?

Answer 26

lesions of the brainstem

Question 27

what is the name of this reflex -

rapid postural adjustments that are made to stop you falling when you trip

Answer 27

dynamic righting reflex

Question 28

what is the tonic labyrinthine reflex?

Answer 28

keep the axis of the head in the constant relationship with the rest of the body

Question 29

what is the dynamic righting reflex?

Answer 29

rapid postural adjustments that are made to stop you falling over the you trip

Question 30

what is the tonic labyrinthine reflex?

Answer 30

keep the axis of the head in constant relationship with th rest of the body

Question 31

what are the 2 vestibulo-ocular reflexes?

Answer 31

static reflex

dynamic vestibular nystagmus

Question 32

what is the static reflex?

Answer 32

when you tilt your head your eyes introit/extort in order to keep the image the right way up (to an extent)

Question 33

what is the dynamic vestibular nystagmus reflex?

Answer 33

saccadic eye movements that rotate the eye against the direction of rotation so the original gaze is preserved

Question 34

how do you determine the direction of nystagmus?

Answer 34

the direction of the flick back

Question 35

how i nystagmus used to test vestibular function?

Answer 35

post-rotary nystagmus (Barany chair)
caloric stimulation (initiating nystagmus with cold or hot water)

Question 36

does hot or cold water cause the nystagmus to move towards the affected side?

Answer 36

cold water = opposite side

warm water = same side

Question 37

what is kinetosis and what is it due to?

Answer 37

motion sickness

due to maintained stimulation of the vestibular system which causes conflicted signals in the cerebellum