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1B Neurology & Neuroscience > Vestibular system > Flashcards

Vestibular system Flashcards

1
Q

what are the main inputs to the vestibular system?

A

visual

proprioceptive

vestibular information

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2
Q

what are the outputs of the vestibular system?

A

reflexes to maintain stable posture and gaze

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3
Q

where is the vestibular organ?

A

in the posterior area of inner ear

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4
Q

what is located within the vestibular organ?

A

utricle and saccule are located in vestibule and joined by a conduit

saccule also joined by cochlea

3 semi-circular canals on each ear (anterior, posterior and lateral)

semi-circular canals have an ampullar on one side and are connected to utricle

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5
Q

what is the projection of the vestibular organ on the base of skull?

A

superior projection of right bony labyrinth on base of skull

  • Location of vestibular organ draws planes for anterior and posterior canals
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6
Q

what do planes for anterior and posterior canal do?

A

planes determine which structure will be stimulated with a specific head movement

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7
Q

what do vestibular hair cells have?

A

kinocilium (biggest cilium) and stereocilia

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8
Q

what do kinocilium and stereocilia do?

A

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

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9
Q

what are the otolith organs?

A

utricle and saccule

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10
Q

where are the cells located on the otolith organs?

A

cells located on maculae

horizontally in utricle

vertically in saccule

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11
Q

what do the maculae contain?

A

hair cells

gelatinous matrix

otoliths on top

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12
Q

what are otoliths?

A

carbonate crystals that help deflection of the hairs

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13
Q

how are semicircular canals organised?

A
  • Do NOT have otoliths
  • Hair cells in canals are in ampulla
  • Rest of canal only has liquid high in potassium called endolymph
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14
Q

what does the ampulla contain?

A

crista where hair cells are located

cells surrounded by cupula which helps hair cell movements

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15
Q

what is the orientation of the canals?

A

defines 3 planes

anterior and posterior canals for 90 deg angle

lateral canals are horizontal to other canals

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16
Q

where do the primary afferents of vestibular nerve end?

A

vestibular nuclei and cerebellum

17
Q

where does the vestibular nuclei have projections to?

A
  • spinal cord
  • nuclei of extraocular muscles
  • cerebellum
18
Q

what do hair cells send inputs to?

A

vestibular nuclei-> vestibular cortex

various reflexes also activated:

  • vestibulospinal
  • vestibuloocular
  • vestibulocerebellar
19
Q

what is the vestibular cortex?

A

not one specific area

many cortical areas participate

main processing centre in parietal lobe -> on parieto-insular vestibular cortex (PIVC)

20
Q

how does sensory input to the vestibular cortex to motor output?

A
21
Q

what are the functions of the vestibular system?

A
  1. detect and inform about head movements
  2. keep images fixed in retina during head movements
  3. postural control
22
Q

what are the potentials of hair cells?

A
  • 3 potentials
  • hair cells have resting potential which have basal discharge to nerve
  • hairs moving towards kinocilium= depolarisation
    • increase nerve discharge
  • hairs moving away from kinocilium = hyperpolarisation
    • reduction in nerve discharge
  • each ear side works in opposite ways- when head moves on way- one side excitation, other inhibition
23
Q

what is the function of otolith organs?

A
  • linear acceleration and tilt movements
    • utricle: horizontal
    • saccule: vertical
24
Q

how do the semi-circular canals work?

A
  • angular acceleration
  • endolymph moves thus cupula displacement and displaces hair cells
  • output signal on VIIIth (vestibulocochlear) nerve is velocity
  • work in pairs according to planes
  • both laterals work together
  • anterior from one side work with posterior of other side
25
Q

what is the vestibulo-ocular reflex? (VOR)

A
  • keep image fixed in retina
  • connection between vestibular nuclei and oculomotor nuclei
  • eye movement in opposite direction to head movement
    • same velocity and amplitude
26
Q

what is the vestibulospinal reflex? (VSR)

A
  • compensatory reflex when about to lose balance
    • motor neurons to limb muscles (lateral tract)
    • motor neurons to neck and back muscles (medial tract)
  • postural control and compensatory body movement according to the head position
27
Q

what is the main symptoms of a balance disorder?

A
  • Main symptom is dizziness or vertigo (very common- 25% ENT and neurological referrals)
28
Q

what is vertigo?

A

perception of rotation (spining)

29
Q

what is dizziness?

A

not necessarily spinning sensation

30
Q

how can balance disorders be characterised?

A

based on location of affected structure and evolution of signs and symptoms

31
Q

what are the different locations for balance disorders?

A

peripheral vestibular disorders

  • labyrinth and/or VIII nerve
    • vestibular neuritis
    • BPPV
    • meniere’s disease
    • unilateral and bilateral vestibular hypofunction

central vestibular disorders

  • CNS (brainstem/cerebellum)
    • stroke
    • MS
    • tumour
32
Q

what diseases are seen in different timeframes of balance disorders?

A
  • acute
    • vestibular neuritis
    • stroke
  • intermittent
    • BPPV
  • recurrent​
    • meniere’s disease
    • migraine
  • progressive
    • schwannoma vestibular (VIII nere)
    • degenerative conditions (MS)
33
Q

what are some other causes of dizziness?

A
  • Head disorders
  • Presyncopal episodes
  • Orthostatic hypotension
  • Anaemia
  • Hypoglycaemia
  • Psychologica
  • Gait disorder

1B Neurology & Neuroscience (14 decks)

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