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Neurology and Neuroscience > Vestibular System > Flashcards

Vestibular System Flashcards

1
Q

What three inputs make up the vestibular system?

A
  • Visual
  • Propioceptive
  • vestibular information
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2
Q

What are the outputs within the vestibular system?

A

Reflexes to maintain stable posture and stable gaze

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3
Q

What is the vestibular organ?

A

Posterior area of the inner ear which contains hair cells for hearing and balance

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4
Q

Describe the anatomy of the vestibular organ?

A

Utricule and saccule are located in the vestibule and are joined by a conduit.

The saccule is also joint to the cochlea

There are three semicircular canals on each ear, anterior, posterior and lateral

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5
Q

Describe the anatomy of the semicircular canals?

A

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

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6
Q

What is known as the labyrinth in the skull?

A

Superior projection of right bony labyrinth on the base of the skull

The lcoation of the vestibular organ draws planes for anterior and posterior canals

These planes determine which structure will be simulated with a specific head movement

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7
Q

What is a kinocilium?

A

The biggest cilium hair cell

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8
Q

What type of hair cells make up vestibular hair cells?

A

Kinocilia and sterocilia

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9
Q

What does head movement do to hair cells?

A

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

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10
Q

What are the Otolith organs?

A

Utricle and saccule are the otolith organs, their cells are located on the maculae, placed horizontally in the utricle and vertically in the saccule

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11
Q

What do the maculae contain?

A

Hair cells as a gelatinous matrix and the otholiths on top.

These otholiths are carbonate crystals that help the deflection of the hairs

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12
Q

What are the crista?

A

The ampulla has he crista where the hair cells are located.

The cells are surrrounded by the capula which helps the hair cell movement

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13
Q

Where are the hair cells located in the canals?

A

In the ampulla

The rest of the canal has a liquid high in potassium called endolymph

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14
Q

Describe the planes of the semi-circular planes?

A

The orientation of the canals in the head defines three planes

Anterior, posterior ( which form a 90 degree angle )and lateral canal- which is horizontal to the other canals

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15
Q

Where are the vestibular nuclei?

A

Primary afferents end in vestibular nuclei and in the cerebellum

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16
Q

Where do the vestibular nuclei project to?

A

Spinal cord
Nuclei of the extraocular muscles
Cerebellum
Centres for cardiovascular + respiratory control

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17
Q

Where is the vestibular cortex?

A

There is no one specific area since many inputs and integrators are involved

= many cortical areas participate

18
Q

Where is the main processing centre thought to be?

A

In the parietal lobe

In parieto-insular vestibular cortex = PIVC

19
Q

How to hair cells become depolarised?

A

( has 3 responses, resting excitation and inhibition all which have a discharge/nerve stimulation )

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

–> hairs moving towards the kinocilium generates depolarization and an increase in nerve discharge

20
Q

How does hyperpolarization occur in hair cells?

A

Hairs moving away from kinocilium generates it. And a reduction in nerve discharge

21
Q

How is Otolith movement sensed?

A

It represents linear acceleration and head tilit

22
Q

In what way Utricule movement sensed?

A

Horizontal movement

23
Q

In what way is the saccule movement sensed?

A

Verticle movement

24
Q

How is angular acceleration sensed?

A

(semicircular canals)

Capulla moves and displaces hair cells

Output signal on 8th nerve is of velocity

25
Q

How do Semicircular canal pairs work?

A

SCC pairs:

work in accordance to the planes

Both lateral

Anterior on one side and posterior on opposite side

26
Q

What is the vestibulo-ocular reflex?

A

Keeps images fixed in the retina

Connection between vestibular nuceli and oculomotor nuclei

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

27
Q

What is the vestibulo-spinal reflex?

A

Motor neurons to limb muscles - lateral tract

Motor neurons to neck and back muscles - medial tract

Controls POSTURAL CONTROL, avoidance of falls and compensatory body movement according to head position

28
Q

What vestibular tests can be done?

A
  • Caloric test
  • Video head impulse test
  • Vestibular evoked myogenic potential
  • Rotational test
29
Q

How is the vestibular system assessed?

A
  • Anamnesis
  • Posture and gait
  • Cerebellar function
  • Eye movements
30
Q

What is balance disorder?

A

causes:
Dizziness or vertigo

Very common - 25% of ENT referrals

31
Q

How is balance disorder cathegorised?

A

Location of the affected structure and evolution of signs and symptoms

32
Q

What location based balance disorders are there?

A

Peripheral vestibular disorders

Labyrinth and/or 8th nerve

OR

Central vestibular disorders

CNS, brainstem/cerebellum

33
Q

What evolution based balance disorders are there?

A

Acute
Recurrent
Intermittent
Progressive

34
Q

Give examples of Peripheral vestibular disorders?

A
  • Vestibular neuritis
  • Benign paroxysmal positional vertigo BPPV
  • Meniere’s disease
  • Unilateral and bilateral vestibular hypofunction
35
Q

Give examples of CNS vestibular disorders?

A
  • Stroke
  • MS
  • Tumours
36
Q

Give an example of an acute balance disorders? (2)

A

Vestibular neuritis

Stroke

37
Q

Give an example of a recurrent balance disorders? (2)

A

Meniere’s Disease

Migraine

38
Q

Give an example of an intermittent balance disorders?

A

Benign Paroxysmal Positional Vertigo (BPPV)

39
Q

Give an example of a progressive balance disorders? (2)

A 
Schwannoma vestibular (VIIIth nerve)
Degenerative conditions (MS)
40
Q

What other causes can there be if a px complains of dizzyness?

A

could be:

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

Neurology and Neuroscience (21 decks)

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