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y2 lcrs neuro fwong hr > The vestibular system > Flashcards

The vestibular system Flashcards

1
Q

What medical term is used to describe instability?

A

Vestibular ataxia

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2
Q

What is the vestibulospinal reflex?

A

Reflex balance reaction to sudden instability of gait/ posture

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3
Q

What is the vestibulo-ocular reflex?

A

Reflex that preserves visual acuity during head-movement

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4
Q

Recall the vestibular system nerve supply of the extraocular muscles

A

Superior and medial vestibular neurons

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5
Q

Recall the pathway of the vestibulo-ocular reflex

A

Abducens nerve: abduction of one eye
CNVI excites contralateral oculomotor nucleus
Other eye adducted

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6
Q

Other than the vestibulo-spinal and vestibulo-ocular reflexes, name 3 functions of the vestibular system

A
  • BP and HR control during rapid up/down tilts
  • Synchronises respiration with body orientation
  • Provoke motion sickness
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7
Q

What are the 2 principle components of the vestibular system?

A

Otolith organs

Semi-circular canals

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8
Q

What is sensed by the otolith organs?

A
  1. Acceleration of head

2. Strength + direction of gravity

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9
Q

What are the main components of the otolith organs?

A

Otolith hair cells
Saccule
Utricle

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10
Q

What is the saccule?

A

Bed of hair cells in inner ear

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11
Q

What is detected by the saccule?

A

Linear accelerations and head tilts in VERTICAL plane

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12
Q

What overlays the otolith hair cells?

A

Otoconia

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13
Q

Describe the cilia found on otolith hair cells

A

Each hair cell has one kinocilia and many stereocilia

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14
Q

Describe the directional sensitivity of otolith hair cells

A

All combinations of lateral and antero-posterior directions

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15
Q

What stimulates the otolith hair cells?

A

Internal resistance of the otoconia to head acceleration

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16
Q

Describe the orientation of the utricle and the cells within it

A

Oriented horizontally with hair cells projecting vertically

17
Q

What is sensed by the semi-circular canals?

A

Angular rotation of head

18
Q

From where do hair cells project in the semi-circular canals?

A

Ampullae

19
Q

Describe how the semicircular canals differentiate acceleration and deceleration

A

Acceleration to the right stimulates canals on the right whilst deceleration to the right stimulates canals to the left, and vice versa

20
Q

How do semi-circular canals ensure a balance of firing when the head is upright?

A

Fire at tonic firing rate

21
Q

What are the semi-circular canals stimulated by?

A

Rotation in their own plane

22
Q

What gives signal to the brain of linear acceleration in all 3D directions overall?

A

Vector sum of utricular and saccular patterns

23
Q

Define vertigo

A

False perception of movement in space

24
Q

Recall the normal neural pathway of vestibular projections

A

–> hypothalamus –> spatial cortex

25
Q

Where is the spatial cortex?

A

Tempero-parietal region

26
Q

Define oscillopsia

A

Inability to stabilise eyes during head movement in bilateral vestibular legion

27
Q

Describe the main symptom of oscillopsia

A

Objects in visual field appear to oscillate

28
Q

What is the main consequence of unilateral loss of vestibular function?

A

Severe nausea and vomiting

29
Q

What medical term is given for an inability to stabilise the eyes?

A

Vestibular nystagmus

30
Q

What causes vestibular nystagmus

A

One intact canal has an unopposed tonus

31
Q

Describe the onset of visual nystagmus

A

Intact canal has an unopposed tonus –> eyes therefore driven to SIDE OF LESION as normal vestibulo-occular reflex
o Drifting movement is detected by the brainstem
 intermittent “resetting” of eye position with fast saccades
 rapid involuntary eye movement

32
Q

Describe the onset of vertigo

A

• Tonus of the intact canal = signal that head is rotating to intact side
- causes feeling of intense spinning

33
Q

Recall 2 symptoms of a bilateral vestibular lesion

A

Oscillopsia

Mild gait ataxia

y2 lcrs neuro fwong hr (17 decks)

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