Vestibular System

Question 1

The vestibular system includes what three inputs?

Answer 1

visual
proprioceptive
vestibular information

Question 2

What are the main outputs of the vestibular system?

Answer 2

reflexes to maintain a stable posture and stable gaze

Question 3

Where is the vestibular organ located?

Answer 3

posterior area of the inner ear

Question 4

What important structures are located in the vestibule? What are they joined by?

Answer 4

utricle
saccule
joined by a conduit

Question 5

Name the three semicircular canals on each ear.

Answer 5

anterior
posterior
lateral

Question 6

What do the semi circular canals have on one side? What are they connected by?

Answer 6

ampulla

utricle

Question 7

where does the vestibular organ sit in the skull?

Answer 7

superior projection of right bony labyrinth in the temporal bone on the base of the skull

Question 8

the plane of the anterior semi circular canal meets the plane of the posterior semi circular canal at what angle?

Answer 8

90 degrees

perpendicular

Question 9

the planes of the anterior + posterior semi circular canals determine what?

Answer 9

which structure will be stimulated with a specific head movement

Question 10

list types of cilia the vestibular hair cells have

Answer 10

kinocilium (biggest)

stereocilia

Question 11

function of cilia

Answer 11

allows the cells to depolarise with movement of the endolymph generated by head movement

Question 12

what is the utricle?

Answer 12

larger of the two fluid-filled cavities forming part of the labyrinth of the inner ear

Question 13

what is the saccule?

Answer 13

smaller of the two fluid-filled cavities forming part of the labyrinth of the inner ear

Question 14

list the otolith organs

Answer 14

utricle

saccule

Question 15

define otolith

Answer 15

each of three small oval calcareous bodies in the inner ear, involved in sensing gravity and movement

Question 16

where are the cells of the utricle and saccule located?

Answer 16

on the maculae

Question 17

how are the cells oriented in the utricle?

Answer 17

horizontally

Question 18

how are the cells oriented in the saccule?

Answer 18

vertically

Question 19

the maculae contain?

Answer 19

hair cells
gelatinous matrix
otoliths on top

Question 20

function of otoliths

Answer 20

are carbonate crystals that help the deflection of the hairs

Question 21

where are the hair cells in the canal located?

Answer 21

ampulla

Question 22

name the liquid in the canal

Answer 22

endolymph

Question 23

endolymph is rich in?

Answer 23

potassium

Question 24

where is the crista?

Answer 24

in the ampulla

Question 25

what is the crista?

Answer 25

the sensory organ of rotation

Question 26

function of the crista

Answer 26

sense angular acceleration and deceleration

Question 27

the hair cells are surrounded by the matrix called?

Answer 27

cupula

Question 28

do the semi circular canals have otoliths?

Answer 28

no

Question 29

describe the orientation of the lateral canals to the anterior and posterior canals

Answer 29

horizontal to the other canals | the planes of the anterior and posterior canals meet at 90 degrees

Question 30

primary afferents to the vestibular organ end in?

Answer 30

vestibular nuclei and in the cerebellum

Question 31

vestibular nuclei have projections to?

Answer 31

spinal cord nuclei of the extraocular muscles cerebellum centres for cardiovascular + respiratory control

Question 32

list the four main vestibular nuclei

Answer 32

superior lateral medial inferior

Question 33

information that travels to the superior and lateral vestibular nuclei then goes to the?

Answer 33

ventroposterior nucleus > vestibular cortex

Question 34

list reflexes the vestibular system is responsible for

Answer 34

``` vestibulospinal reflexes (posture) vestibulocerebellar reflexes (coordination/monitoring) vestibulo-ocular reflexes (eye movements in compensation for head movements) ```

Question 35

what area is the vestibular cortex in?

Answer 35

not anywhere specific, many inputs and integrators are involved, many cortical areas

Question 36

where is the main processing centre of the vestibular cortex?

Answer 36

in the parietal lobe | in the parieto-insular vestibular cortex

Question 37

in terms of processing of sensory information, what are the primary and adaptive processors?

Answer 37

primary > vestibular nuclear complex | adaptive > cerebellum

Question 38

list the three main functions of the vestibular system

Answer 38

to detect and inform about head movements postural control to keep images fixed in the retina during head movements

Question 39

how many potentials do hair cells have? name them

Answer 39

3: resting, excitation, inhibition

Question 40

resting potential of the hair cells

Answer 40

basal discharge (neural firing rate) to the nerve

Question 41

excitation of the hair cells

Answer 41

deflection of the hair cells towards the kinocilium > increased nerve discharge > depolarisation

Question 42

inhibition of the hair cells

Answer 42

deflection of the hair cells away from the kinocilium > reduced neural firing rate > hyperpolarisation

Question 43

otolith movement

Answer 43

linear acceleration and tilt (backward and forwards)

Question 44

the utricle is sensitive to movements in what plane?

Answer 44

horizontal

Question 45

the saccule is sensitive to movements in what plane?

Answer 45

vertical

Question 46

the semicircular canals are sensitive to what movement?

Answer 46

angular acceleration

Question 47

how do the semicircular canals detect movement?

Answer 47

movement moves endolymph > cupulla displacement > displaces hair cells > depolarisation or hyperpolarisation

Question 48

what is the output signal on the vestibulocochlear (VIII) nerve?

Answer 48

velocity

Question 49

semicircular canals on both sides of the head work together in what pairs?

Answer 49

both laterals work together | anterior canal from one side works with the posterior canal on the other side (vice versa)

Question 50

what is the vestibulo-ocular reflex?

Answer 50

helps keep the image fixed in the retina despite head movement (head moves, eyes stay still)

Question 51

what is the vestibulo-spinal reflex?

Answer 51

postural control | avoidance of falls compensatory body movement according to head position

Question 52

what nuclei are involved in the vestibulo-ocular reflex?

Answer 52

vestibular | oculomotor

Question 53

connections from nuclei in vestibulo-spinal reflex?

Answer 53

vestibular nuclei > motor neurons > limb muscles (lateral tract) or neck/back muscles (medial tract)

Question 54

assessment of the vestibular system

Answer 54

``` anamnesis (history) posture and gait cerebellar function eye movements symptoms and impact assessment ```

Question 55

list vestibular tests

Answer 55

Caloric test Video head impulse test (vHIT) Vestibular evoked myogenic potential (VEMP) Rotational test

Question 56

imaging used to assess the vestibular system

Answer 56

CT scan | MRI

Question 57

main symptoms of balance disorders?

Answer 57

dizziness | vertigo

Question 58

balance disorders can be categorised based on?

Answer 58

location of the affected structure | evolution of signs and symptoms

Question 59

peripheral vestibular disorders are located where?

Answer 59

labyrinth and/or VIII nerve

Question 60

central vestibular disorders are located where?

Answer 60

CNS (brainstem/cerebellum)

Question 61

list examples of conditions leading to central vestibular disorders

Answer 61

stroke MS tumours

Question 62

list examples of conditions leading to peripheral vestibular disorders

Answer 62

vestibular neuritis Benign Paroxysmal Positional Vertigo (BPPV) Meniere’s disease Unilateral and Bilateral vestibular hypofunction

Question 63

name categories for evolution of signs and symptoms of balance disorders

Answer 63

acute intermittent recurrent progressive

Question 64

list conditions with an acute evolution

Answer 64

``` Vestibular Neuritis (‘labyrinthitis’) Stroke ```

Question 65

list conditions with an intermittent evolution

Answer 65

Benign Paroxysmal Positional Vertigo (BPPV)

Question 66

list conditions with a recurrent evolution

Answer 66

Meniere’s Disease | Migraine

Question 67

list conditions with a progressive evolution

Answer 67

``` Schwannoma vestibular (VIIIth nerve) Degenerative conditions (MS) ```

Question 68

what are other reasons, apart from vestibular dysfunction, for dizziness?

Answer 68

``` heart disorders presyncopal episodes orthostatic hypotension anaemia hypoglycaemia psychological gait disorders ```