Z YEAR 2 BRS NEURO > Vestibular System > Flashcards

Vestibular System Flashcards

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1
Q

What are the three main inputs to the vestibular systems?

A
  1. visual
  2. proprioceptive
  3. vestibular information
    - Pressure, vision, rotation and gravity
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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

  • Ocular reflex, postural control
  • CNS integrates the information and generates the responses
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3
Q

Where is the vestibular organ in the ear?

A
  • posterior area of the inner ear - petrous portion temporal bone
  • Still hair cells
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4
Q

Where are the utricle and saccule located?

A
  • in the vestibule and are joined by a conduit

- saccule is also joined to the cochlea

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5
Q

What are the three semi-circular canals on each ear?

A

anterior, posterior and lateral

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6
Q

What do the semicircular canal have?

A

an ampulla on one side, and they are connected to the utricle

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7
Q

Where is the vestibular organ in the skull?

A
  1. Superior projection of right bony labyrinth on base of skull
  2. The location of the vestibular organ draws planes for anterior and posterior canals
  3. These planes determine which structure will be stimulated with a specific head movement.
    - 5 head movements structures, to generate right movement so planes are important
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8
Q

What do vestibular cells have?

A
  • kinocilium (the biggest cilium)

- stereocilia (all orientated to one side)

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9
Q

What do the cilia allow?

A

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

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10
Q

What are the otolith organs?

A
  • Utricle

- saccule

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11
Q

How are the utricle and sacuule cells located?

A

on the maculae, placed horizontally in the utricle and vertically in the saccule

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12
Q

What does the maculae contain?

A

contain the hair cells, a gelatinous matrix and the otoliths on top

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13
Q

What are otholiths?

A

carbonate crystals that help the deflection of the hairs

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14
Q

Do semicircular cells have otholiths?

A

NO

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15
Q

Where are the hair cells in the canals located?

A

In the ampulla

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16
Q

What does. the rest of the canal have?

A

endolymph (liquid high in K+)

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17
Q

What is in the ampulla? What are the cells surrounded by?

A
  • crista, where the hair cells are located
  • cells are surrounded by the cupula which helps the hair cell movement
  • The endolymph will push the cupula to one side or another will help deflection of. hairs
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18
Q

Why is the orientation of the semi-circular planes important?

A
  • The orientation of the canals in the head defines three planes
  • Anterior and posterior canals form a 90° angle
  • Lateral canals are horizontal to the other canals.
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19
Q

Where do the primary afferent. end?

A

in vestibular nuclei (in brainstem) and in the cerebellum

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20
Q

Where do vestibular nuclei have projections to?

A
  1. Spinal cord
  2. Nuclei of the extraocular muscles
  3. Cerebellum
  4. Centres for cardiovascular + respiratory control
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21
Q

What are the vestibular reflexes?

A
  1. Vestibulospinal reflexes
  2. Vestibulocerebellar reflexse
  3. Vestibulo-ocular refelx (VOR.
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22
Q

What is the vestibular cortex?

Study These Flashcards
A
  • Not one specific area

- Since many inputs and integrators are involved, many cortical areas participate

23
Q

What is the main processing. area for the vestibular system?

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A

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

24
Q

What is the vestibular system functions?

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A
  1. To detect and inform about head movements
  2. To keep images fixed in the retina during head movements
  3. Postural control
25
What. are the inputs of the.vestibular system?
1. Visual 2. Proprioceptive 3. Vestibular information
26
What is the resting potential of the hair cells?
- has a basal discharge to the nerve | - Even when resting and not moving
27
What are the three states of hair potential?
1. Resting 2. Excitation 3. Inhibition
28
What do hairs moving towards the kinocilium generate?
generates depolarization and an increase in nerve discharge
29
What do hairs moving away from the kinocilium generate?
generates hyperpolarization and a reduction in nerve discharge
30
Why two ears?
If head moving in one direction one ear may be excitatory and other inhibitory and quick response - tell same info to vestibular nuclei
31
What does otolith movement refer to?
Linear acceleration (vertical or horizontal) and tilt
32
What happens in a head tilt backward or forward?
depolarisation or hyperpolarisation which will induce increase or decrease firing rate which will allow us to make adjustment e.g. in neck muscle
33
What happens in acceleration or deceleration with no. head tilt?
Still causes movement of hair cells so depolarisation
34
What is the utricle sensitive to?
Horizontal movement plane
35
What is the saccule sesntive. to?
Vertical movement plane
36
What type of acceleration do semicircular canals react to?
-Angular acceleration
37
What happens when we move. head in angular acceleration?
1. Endolymph move 2. Cupula displacement and displaces hair cells causes depoalrisation/hyperpolarisation which goes to brain stem
38
What is the output signal from semicircular canals?
on VIIIth (vestibulocochelar) nerve is velocity
39
How do the laterals work in pairs?
anterior from. one side with posterior of the opposite side e.g. right posterior with left anterior
40
How do SCC work?
work in pairs according to the planes
41
What are the two vestibular reflexes?
1. Vestibulo-ocular reflex (VOR) - quickest | 2. Vestibulo spinal reflex (VSR)
42
How does VOR work?
- Reading when moving 1. Keeps images fixed in the retina 2. Connection between vestibular nuclei and oculomotor nuclei 3. Eye movement in opposite direction to head movement, but same velocity and amplitude
43
What is the VSR?
1. Motor neurons to limb muscles (lateral tract) 2. Motor neurons to neck and back muscles (medial tract) 3. Postural control, avoidance of falls and compensatory body movement according to the head positio
44
What are the vestibular tests?
◦Caloric test - stimulates inner ear - nystagmus and dizziness - hard to tolerate but good to tell you if work or not working. can do both organs separately ◦Video head impulse test (vHIT) (both organs) about inner ear - simple quick and tolerate better ◦Vestibular evoked myogenic potential (VEMP) - neck and vestibular system ◦Rotational test, big equipment needed
45
What imaging is used?
CT scan, MRI
46
What is balance disorder?
1. Main symptom is dizziness or vertigo (spinning sensation) 2. Can be categorised based on location of the affected structure and evolution of signs and symptoms. 3. Very common, 25% of ENT and neurological referrals
47
How do you assess vestibular system?
Check and test: 1. Anamnesis (history) 2. Posture gait 3. Cerebellar function 4. Eye movements
48
What do you think for Peripheral vestibular disorders (labyrinth and/or VIII) nerve location?
1. vestibular neuritis 2. Benign Paroxysmal Positional Vertigo (BPPV) 3. Meniere’s disease (hearing and balance affected) 4. Unilateral and Bilateral vestibular hypofunction
49
What do you think for Central vestibular disorders/CNS (brainstem/cerebellum) location?
1. Stroke 2. MS 3. tumours
50
What would you think if the symptoms are acute?
1. Vestibular Neuritis (‘labyrinthitis’) | 2. Stroke
51
What would you think if the symptoms are intermittent?
Benign Paroxysmal Positional Vertigo (BPPV)
52
What would you think if the symptoms are recurrent?
1. Meniere’s Disease | 2. Migraine
53
What would you think if the symptoms are progressive?
1. Schwannoma vestibular (VIIIth nerve) | 2. Degenerative conditions (MS)
54
What else could dizziness be?
Not necessarily vestibular: 1. Heart disorders 2. Presyncopal episodes 3. Orthostatic hypotension 4. Anaemia 5. Hypoglycaemia 6. Psychological 7. Gait disorders
Z YEAR 2 BRS NEURO
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