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BRS YEAR 2 > Neuro - Vestibular System > Flashcards

Neuro - Vestibular System Flashcards

1
Q

What are the main inputs of the vestibular system

A

Visual
Proprioceptive (pressure)
Vestibular (rotation and gravity)

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2
Q

What is the role of the CNS in the vestibular system

A

Processes inputs and integrates them to generate responses

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3
Q

What are the outputs of the vestibular system

A

Ocular reflex and postural control to keep an image fixed when we move, and to stop us falling over when moving

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4
Q

Where is the vestibular organ found

A

In the posterior area of the middle ear

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5
Q

What does the inner ear contain?

A

Hair cells for hearing and balance

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6
Q

What makes up the vestibule

A

The utricle and saccule make up the vestibule which us the entrance to the inner ear

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7
Q

What joins the utricle and saccule

A

A conduit

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8
Q

What is the saccule joined to

A

Cochlea

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9
Q

What are the semicircular canals connected to

A

These each have an ampulla on one side and are connected to the utricle

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10
Q

What is the need for having the semicircular canals in different planes

A

This gives us planes so that specific structures are stimulated with specific head movements. This means that we can have more focused reflexes to help maintain our ocular reflex and postural control

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11
Q

What is the kinocilium

A

The biggest cilium, typically found adjacent to other stereocilia

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12
Q

How does depolarisation of vestibular hair cells arise?

A

When the head moves, the liquid inside the inner ear (endolymph) moves and causes hair cell deflection either towards or away from the kinocilium. Stereocilium movement towards the kinocilium means that we get depolarisation

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13
Q

What does greater head movement mean in terms of depolarisation?

A

Greater head movement leads to greater hair cell deflection and thus greater depolarisation

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14
Q

What are otolith organs

A

Utricle and saccule both otolith organs

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15
Q

Where are the hair cells of the utricle located

A

In the maculae found horizontally

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16
Q

Where are the hair cells of the saccule located

A

In the maculae found vertically

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17
Q

What do the maculae contain

A

Contain the hair cells, a gelatinous matrix and then the otoliths on top

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18
Q

What are otoliths

A

Carbonate crystals that help with the movement of hairs

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19
Q

Where are hair cells in canals located

A

Located in the crista ampullaris (of the ampulla)

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20
Q

What is the cupula

A

Surrounds the hair cells and help hair cell movement by closing the ampulla so that endolymph can move it to help with the deflection of hair cells

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21
Q

Where do primary afferents for the vestibular nerve end up

A

In the vestibular nuclei and the cerebellum

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22
Q

Where do the vestibular nuclei project?

A

Spinal cord
Nuclei of the extra ocular muscles
Cerebellum
Centres for cardiovascular and respiratory control

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23
Q

What are the 4 vestibular nuclei

A

Superior
Inferior
Medial
Lateral

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24
Q

What reflexes are produced by vestibular afferents travelling via the vestibular nuclei

A

Vestibulospinal reflexes
Vestibulocerebellar reflexes
Vestibulo-ocular reflex

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25
Q

What is the vestibular cortex

A

Not one specific area - as many inputs and integrators are involved there are several cortical areas which partake

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26
Q

What is the main area of the vestibular cortex

A

Parieto-Insular Vestibular Cortex (PIVC) found in the parietal lobe

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27
Q

What are the 3 main functions of the vestibular system?

A

Detect and inform about head movements
Keep images fixed in the retina during head movement
Postural control

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28
Q

What are the 3 potentials of hair cells

A

Resting potential
Excitations
Inhibition

29
Q

Describe the resting potential of hair cells

A

When we are upright there is still some firing in order to maintain postural control therefore we say there is basal discharge

30
Q

What does hair cells moving towards the kinocilium generate?

A

Depolarisation and an increase in nerve discharge

31
Q

What does hair cells moving away from the kinocilium generate?

A

Hyperpolarisation and a reduction in nerve discharge

32
Q

When one side of the vestibular system is depolarised, what happens to the other side?

A

When one side is depolarised, the other side is inhibited as we are sending the same info to the vestibular nuclei

33
Q

What causes otolith movement?

A

Linear acceleration and tilt

34
Q

What generates basal discharge when the head is upright

A

When we are upright we still have some deflection of hair cells therefore we get a basal discharge in order to keep us upright

35
Q

What type of movement is the utricle sensitive to

A

Horizontal movement

36
Q

What type of movement is the saccule sensitive to

A

Vertical movement

37
Q

What does depolarisation/ hyperpolarisation allow for

A

Allows for compensatory movement

38
Q

What impact does angular acceleration have

A

If we move the head, endolymph moves and displaces the cupula therefore helps displace hairs to cause depolarisation or hyperpolarisation to send info to the brainstem. Therefore the SSC are responsible for angular acceleration

39
Q

What is the output signal from angular acceleration

A

Velocity from the vestibulocochlear nerve

40
Q

How do SSC work in pairs?

A

According to the planes - when one side is stimulated the other is inhibited therefore the left anterior works with the right posterior as they are in the same plane

41
Q

What is the VOR

A

Vestibulo - ocular reflex. Allows us to keep the image fixed during head movement in the retina

42
Q

What is the VSR

A

Vestibulospinal reflex
Works when we are about to lose balance e.g. if we are walking we will get muscle relaxation or contraction to keep our posture

43
Q

What neural connection does the VOR rely upon

A

Connection between vestibular nuclei and the oculomotor nuclei

44
Q

What are the mechanics of the VOR

A

Eye movement occurs in the opposite direction to head movement, but it occurs at the same velocity and amplitude

45
Q

What is the neural connection is the VSR dependent on

A

There is a motor connection to the limb muscles (lateral tract) and to the neck and back muscles (medial tract)

46
Q

What are the mechanics of the VSR

A

Postural control by avoiding falls and compensatory body movement according to the head position

47
Q

What does assessment of the vestibular system contain?

ACE VIPS

A 
Anamnesis 
Posture and gait
Cerebellar function
Eye movement 
Vestibular tests
Imaging (CT, MRI)
Symptoms
48
Q

What is anamnesis

A

History - some disorders are so specific that you can get a clear diagnosis straight away

49
Q

What vestibular tests can we perform

A

Caloric test
Video head impulse test
Vestibular evoked myogenic potential
Rotational test

50
Q

What is the caloric test

A

Stimulate the inner ear with different temperatures to generate nystagmus or dizziness - we are seeing if eye movement is symmetrical

51
Q

What is the vHIT

A

Video head impulse test - tests both the vestibular organs and is generally tolerated well

52
Q

What is the VEMP

A

Tests the neck muscles - if we get no neck response then we may have vestibular problems

53
Q

What is the rotational test

A

Good but requires more equipment - char with rotary motor is used to see if we can generate a vestibular response

54
Q

What are the main symptoms of balance disorders

A

Dizziness or vertigo - very common (occur in 25% of ENT and neurological referrals)

55
Q

What is vertigo

A

Perception of rotation

56
Q

What is dizziness

A

More vague than vertigo - related to vertigo but also may include blurry vision, nausea or general vertigo

57
Q

Hoe can we categorise balance disorders

A

Location of the affected structure of the evolution of signs and symptoms

58
Q

Where do peripheral vestibular disorders occur

A

Labyrinth and/or VIII nerve

59
Q

Where do central vestibular disorders occur

A

CNS (brainstem or cerebellum)

60
Q

What are examples of peripheral vestibular disorders

A

Vestibular neuritis
BPPV
Meniere’s
Unilateral and bilateral vestibular hypo-function

61
Q

What is BBPV

A

Benign paroxysmal positional vertigo - the abnormal presence of otoliths in the canal

62
Q

What is Meniere’s disease

A

Increase in liquid in the inner ear therefore the tympanic membrane breaks and we get cell intoxication

63
Q

What are examples of central vestibular disorders

A

Stroke
MS
Tumours e.g. vestibular schwannoma

64
Q

How do we classify ventricular disorders based on evolution

A

Acute
Intermittent
Recurrent
Progressive

65
Q

What acute vestibular disorders can we get

A 
Vestibular neuritis (labyrinthitis)
Stroke
66
Q

What intermittent vestibular disorders can we get

A

BPPV - comes and goes whenever someone moves their head

67
Q

What recurrent vestibular disorders can we get

A
  • Meniere’s (crisis = liquid ruptures membrane, but then the membrane can rebuilt in-between crises)
  • Migraine (vestibular migraine)
68
Q

What progressive vestibular disorders can we get

A 
Schwannoma vestibular (VIIII nerve)
Degerative condition e.g MS
69
Q

What can be other reasons for dizziness aside form vestibular problems (7)

A 
Heart disorders
Presyncopal episodes 
Orthostatic hypotension 
Anaemia
Hypoglycaemia
Psychological
Gait disorders

BRS YEAR 2 (37 decks)

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