Neuro - Vestibular System

Question 1

What are the 3 main inputs for the vestibular system?

Answer 1

→ visual
→ proprioceptive
→ vestibular

Question 2

What are the main outputs of the vestibular system?

Answer 2

reflexes to maintain stable posture + gaze

Question 3

What does the CNS do with the inputed info?

Answer 3

CNS integrates info + generates responses

Question 4

Where is the vestibular organ located?

Answer 4

posterior area of the inner ear

Question 5

Why does the inner ear contain hair cells?

Answer 5

for balance + hearing

Question 6

What are the different parts of the vestibular organ?

Answer 6

→ anterior semi-circular canal
→ lateral semi-circular canal
→ posterior semi-circular canal
→ utricle
→ saccule

Question 7

What makes up the vestibule?

Answer 7

utricle + saccule, joined by a conduit

Question 8

What is connected to the semi-circular canals?

Answer 8

connected to the utricle on one side

Has an ampulla on the other side

Question 9

What is connected to the saccule?

Answer 9

cochlea

Question 10

What is the labyrinth?

Answer 10

superior bony projection on base of skull near inner ear

Question 11

Why is the location of the vestibular organ important?

Answer 11

→ draws planes for anterior + posterior canals

→ planes determine which structure is stimulated for each specific head movement

Question 12

What are the different types of hair on vestibular hair cells?

Answer 12

→ kinocilium (biggest cilium)

→ stereocilia

Question 13

What is the purpose of the cilia?

Answer 13

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

Question 14

What are the otolith organs?

Answer 14

→ utricle

→ saccule

Question 15

Where are the cells of the otolith organs located + arranged?

Answer 15

maculae:
→ placed horizontally in utricle
→ placed vertically in saccule

Question 16

What does the maculae contain?

Answer 16

→ hair cells
→ gelatinous matrix
→ otoliths on top (carbonate crystals that help with deflection of hair cells)

Question 17

What are the otoliths and what is their purpose?

Answer 17

carbonate crystals that help with deflection of hair

Question 18

Where are the hair cells located in the semi-circular canals?

Answer 18

crista of the ampulla

Question 19

What are hair cells aided by in the semi-circular canals?

Answer 19

cupula (helps with hair cell movement)

Question 20

Where do the primary afferent form the vestibular organ end up?

Answer 20

vestibular nuclei + cerebellum

Question 21

Where does the vestibular nuclei project to?

Answer 21

→ spinal chord
→ nuclei of the extra-ocular muscles
→ cerebellum
→ centres for cardiovascular + respiratory control

Question 22

What makes up the vestibular cortex?

Answer 22

→ not one specific area

→ many inputs + integrators are involved = many cortical areas participate

Question 23

Where is the main processing centre thought to be for the vestibular cortex?

Answer 23

Parieto-Insular vestibular cortex (PIVC)

In the parietal lobe

Question 24

What are the functions of the vestibular system?

Answer 24

→ to detect + inform about head movements
→ to keep images fixed in the retina during head movement
→ postural control

Question 25

Why do hair cells have a resting potential?

Answer 25

Has a basal discharge

Question 26

How do hair cells generate depolarisation? How does this effect nerve discharge?

Answer 26

Hairs move towards kinocilium, generate depolarisation + increase in nerve discharge

Question 27

How do hair cells generate hyperpolarisation? How does this effect nerve discharge?

Answer 27

Hairs move away from kinocilium, generate hyperpolarisation + decrease in nerve discharge

Question 28

What is responsible for keeping the head level during linear acceleration + tilt?

Answer 28

otolith organs + movement

Question 29

What is the utricle responsible for?

Answer 29

horizontal movement

Question 30

What is the saccule responsible for?

Answer 30

vertical movement

Question 31

When do the kinocilium bend backwards?

Answer 31

→ head tilt backwards | → acceleration with no head tilt

Question 32

When do the kinocilium bend forwards?

Answer 32

→ head tilt forwards | → decceleration with no head tilt

Question 33

What is responsible for angular acceleration?

Answer 33

semi-circular canals

Question 34

How do the semi-circular canals aid with angular acceleration?

Answer 34

cupulla moves + displaces hair cells

Question 35

What is the output signal from the vestibular nerve during angular acceleration?

Answer 35

velocity

Question 36

How do the SCCs work?

Answer 36

in pairs according to planes: → both lateral on each side → anterior from one side works with posterior from other side + vice versa

Question 37

What are the 2 main vestibular reflexes?

Answer 37

→ VOR (vestibulo-ocular reflex) | → VSR (vestibulo spinal reflex)

Question 38

What is the VOR?

Answer 38

→ keeps images fixed in the retina → connection between vestibular nuclei + oculomotor nuclei → eye movement in opposite direction to head movement but keeps the same velocity + amplitude

Question 39

What is the VSR?

Answer 39

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

Question 40

What tract do the motor neurones from the vestibular nuclei to the limb muscles take?

Answer 40

lateral tract

Question 41

What tract do the motor neurones from the vestibular nuclei to the neck + back muscles take?

Answer 41

medial tract

Question 42

How do you assess the vestibular system?

Answer 42

``` → anamnesis → posture and gait → cerebellar function → eye movements → vestibular tests → imaging, CT scan, MRI → symptoms + impact assessments ```

Question 43

What are the various vestibular tests?

Answer 43

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

Question 44

What are the symptoms of balance disorder?

Answer 44

→ dizziness | → vertigo

Question 45

How is balance disorder categorized?

Answer 45

→ location of affected structure | → evolution of signs + symptoms

Question 46

What are the two different types of balance disorders based on location?

Answer 46

→ peripheral vestibular disorders (labyrinth and/or vestibular nerve affected) → central vestibular disorders (CNS : brainstem/cerebellum affected)

Question 47

What are examples of peripheral vestibular disorders?

Answer 47

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

Question 48

What are examples of central vestibular disorders?

Answer 48

→ stroke → MS → tumours

Question 49

What's an example of an acute balance disorder?

Answer 49

→ Vestibular Neuritis (‘labyrinthitis’) | → Stroke

Question 50

What's an example of an intermittent balance disorder?

Answer 50

Benign Paroxysmal Positional Vertigo (BPPV)

Question 51

What's an example of an recurrent balance disorder?

Answer 51

→ Meniere’s Disease | → Migraine

Question 52

What's an example of an progressive balance disorder?

Answer 52

→ Schwannoma vestibular (VIIIth nerve) | → Degenerative conditions (MS)

Question 53

What can dizziness also be a symptom of other conditions or disorders?

Answer 53

``` → Heart disorders → Presyncopal episodes → Orthostatic hypotension → Anaemia → Hypoglycaemia → Psychological → Gait disorders ```