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NEUROLOGY AND NEUROSCIENCE 2 > VESTIBULAR SYSTEM > Flashcards

VESTIBULAR SYSTEM Flashcards

1
Q

What are the 3 main inputs of the vestibular system?

A

Visual, proprioceptive and vestibular (rotation and gravity) information

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2
Q

What are the outputs of the vestibular system?

A

Mainly reflexes to maintain a stable posture and stable gaze

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3
Q

Where is the vestibular organ located?

A

Posterior area of the inner ear called the labyrinth

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4
Q

Describe the structure of the vestibular organ

A

Utricle and saccule located in vestibule and joined together by conduit. Saccule also joined to cochlea by conduit.
Each ear also has 3 semicircular canals which have an ampulla on one side and are connected to the utricle

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5
Q

What are the 3 semi-circular canals called?

A

Anterior semi-circular canal
Lateral semi-circular canal
Posterior semi-circular canal

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6
Q

How is the labyrinth positioned in the skull?

A

Superior projection on base of skull

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7
Q

How is specific head movement distinguished by the vestibular organ?

A

The orientation of the semi-circular canals draws planes. A movement in each plane will stimulate the structures giving a map of how the head is moving.

The utricle, saccule and the 3 semi-circular canals gives 5 structures which work independently

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8
Q

What is the largest cilium on vestibular hair cells called?

A

Kinocilium

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9
Q

How is movement of the head sensed?

A

Movement of head causes movement of endolymph which shifts the hair cell’s cilia. The bigger the movement the bigger the depolarisation/hyperpolarisation

If stereocilia move towards the kinocilium the cell depolarises and vice versa.

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10
Q

Which organs of the vestibular organ are otolith organs?

A

Utricle and saccule

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11
Q

What are otoliths and what do they do?

A

Calcium carbonate crystals located on top of hair cells and gelatinous matrix. They help to deflect the hairs by adding weight

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12
Q

What does the maculae contain and where is it located?

A

Contains the hair cells, a gelatinous matrix and otoliths on top.

Horizontal in the utricle and vertical in the saccule

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13
Q

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

A

Ampulla - rest of the canal only has endolymph

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14
Q

Describe the structure of the ampullas

A

Hair cells located in the crista.
Cells surrounded by the cupula.

One end of ampulla leads to semi-circular canal and other end to the utricle

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15
Q

What sit the cupula?

A

Gel like substance surrounding the hair cells of the ampulla (canals) which helps with hair cell movement

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16
Q

Describe the planes formed by the canals

A

Anterior and posterior canals/planes form a 90 degree angle with the lateral canal/plane horizontal to them

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17
Q

Where do primary vestibular afferents from hair cells end/lead to?

A

Vestibular nuclei in the brainstem

Cerebellum for coordination and feedback

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18
Q

Where does the vestibular nuclei project to?

A

Spinal cord
Nuclei of the extraocular muscles (eye movement)
Cerebellum
Centres of cardiovascular + respiratory control

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19
Q

Where is the vestibular cortex located?

A

Not one specific area since many inputs and integrators involved spread over many cortical areas

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20
Q

What/where is the main processing centre of the vestibular system located?

A

Parietal lobe, in the Parieto-Insular Vestibular Cortex (PIVC)

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21
Q

What are then 3 functions of the vestibular system?

A

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

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22
Q

How does the head know if it is not moving?

A

Hair cells have resting potential which gives a basal discharge to the nerve

23
Q

What causes otolith movement?

A

Linear acceleration and tilt

24
Q

What type of movement is the utricle sensitive to?

A

Horizontal movement e.g. travelator

maculae is horizontal

25
Q

What type of movement is the saccule sensitive to?

A

Vertical movement e.g. lift

maculae is vertical

26
Q

What are the semi-circular canals sensitive to?

A

Angular acceleration e.g. rotating head

Cupulla moves and displaces hair cells

27
Q

What is the output signal on CN VIII (vestibulocochlear)?

A

Velocity

28
Q

How are the semicircular canals/planes paired?

A

Horizontal canals on either side
Posterior on one side and anterior on the other
Anterior on one side and posterior on the other

29
Q

How do the semi-circular canal/planes pairs work?

A

When one side is excited, the other is inhibited

30
Q

How does the vestibulo-ocular reflex (VOR) work and its function?

A

Keeps images fixed in retina through connection between vestibular nuclei and oculomotor nuclei

Eye movement in opposite direction to head movement but same velocity and amplitude

31
Q

How does the vestibulo spinal reflex (VSR) work and its function?

A

Motor neurons to limb muscles (lateral tract)
Motor neurons to neck and back muscles (medial tract)

Postural control, avoidance of falls and compensatory body movement according to head position

32
Q

List the things you can assess for the vestibular system

A

Anamnesis (history)
Posture and gait
Cerebellar function
Eye movements

33
Q

List the tests that can be carried out to investigate a patient’s vestibular system

A

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

34
Q

What is the caloric test?

A

Stimulate inner ear with different temperatures to generate eye movement. Allows for the test of vestibular organs independently

35
Q

What is the vestibular evoked myogenic potential (VEMP)?

A

See if neck muscles have response if vestibular organ is stimulated

36
Q

What imaging can you carry out to investigate a patient’s vestibular system?

A

CT, MRI

37
Q

What are the symptoms of balance disorder?

A

Dizziness, vertigo

38
Q

What is the difference between dizziness and vertigo?

A

Dizziness is the feeling of light-headedness, unbalanced or wooziness. Vertigo is a specific form of dizziness where you experience spinning sensation

39
Q

What are the two types of balance/vestibular disorders based off location and what is affected?

A

Peripheral vestibular disorders (labyrinth, CN VIII)

Central vestibular disorders (CNS e.g. brainstem/cerebellum)

40
Q

Which location of balance/vestibular disorders is more common and easier to manage?

A

Peripheral vestibular disorders

41
Q

List examples of peripheral vestibular disorders

A

Vestibular nephritis
Benign paroxysmal positional vertigo (BPPV)
Meniere’s disease
Unilateral/bilateral vestibular hypofunction

42
Q

What is benign paroxysmal positional vertigo (BPPV)?

A

Otoliths in the ampulla of semi-circular canals causing exaggerated movement of cupula

43
Q

What is meniere’s disease?

A

Problem with the absorption of endolymph causing fluid build-up in inner ear which breaks the membrane

44
Q

List examples of central vestibular disorders

A

Stroke
Multiple sclerosis
Tumours

45
Q

What are the acute causes of balance/vestibular disorder?

A

Vestibular neuritis

Stroke

46
Q

What are the intermittent causes of balance/vestibular disorder?

A

BPPV - only occurs when head is moved

47
Q

What are the recurrent causes of balance/vestibular disorder?

A

Meniere’s disease - membrane regenerates and cycle continues

Migraine

48
Q

What are the progressive causes of balance/vestibular disorder?

A 
Schwannoma vestibular (CN VIII)
Degenerative conditions e.g. MS
49
Q

What could dizziness also be a sign of?

A 
Heart disorders
Presyncopal episodes
Orthostatic hypotension
Anaemia
Hypoglycaemia
Psychological
Gait disorders
50
Q

List the different vestibular nuclei

A

Superior
Lateral
Medial
Inferior

51
Q

What nuclei does the vestibulospinal reflexes arise from and what is it’s function?

A

Lateral, medial and inferior vestibular nuclei

Posture

52
Q

What nuclei do vestibulocerebellar reflexes arise from and what is it’s function?

A

Superior, lateral, medial and inferior vestibular nuclei

Coordination monitoring

53
Q

What nuclei does the vestibulo-ocular reflex originate from and what is it’s function?

A

Superior, lateral, medial and inferior vestibular nuclei

Eye and head movement

NEUROLOGY AND NEUROSCIENCE 2 (9 decks)

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