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Dental Neuroscience > vestibular system > Flashcards

vestibular system Flashcards

1
Q

anatomy of the ear

A
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2
Q

role of vestibular system

A
  • not prominent conscious sensation
  • reflexes evoked (equilibrium/balance & stabilization of visual field)
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3
Q

2 suborgans of vestibular system

A
  • semicircular canals
  • otolith (macular) organs
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4
Q

semicircular canals function

A
  • sense angular acceleration (turning head)
  • inertial mechanism
  • rapidly adapting (phasic) receptors
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5
Q

otolith (macular) organs

A
  • sense linear acceleration and static position of the head
  • gravitational mechanism
  • slowly adapting (tonic) receptors
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6
Q

semicircular canals structure

A
  • filled with endolymph
  • ampulla
  • crista ampullaris
  • hair cells
  • cupula (watertight seal)
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7
Q

each canal has an expansion called

A

ampulla which contain the endolymph

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8
Q

hair cells are located within

A

the ampulla of the semicircular canals

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9
Q

ampulla is innervated by

A

CN VIII

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10
Q

cupula extends to

A

the top of the ampulla to divide the sides from each other
- important to only allow hair cells to go side to side

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11
Q

hair cells

A
  • flask (I) and tube (II) shapes
  • 1 kinocilium (larger)
  • 100 stereociia (smaller)
  • synaptic vesicles
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12
Q

depolarization and hyper polarization of hair cells

A
  • to depolarize: kinocilium pushed away from stereocilium (then release neurotrasnmitter) because open channels
  • to hyperpolarize: kinocilium pushed toward the stereocilium (less transmitter release) beacuse closed channels
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13
Q

hair cells have ________ firing rate

A

high

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14
Q

signaling to release neurotrasmitters of hair cells

A
  • the kinocilium pulls away from the sterocilia
  • the mechanically gated channels open up
  • K+ to flow in >
  • depolarization >
  • Ca2+ flows in >
  • synaptic vesicles release transmitter into
    synaptic cleft >
  • activation of afferent nerve (CN VIII)
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15
Q

vestibular afferents

A
  • vestibular branch of CN VIII
  • cell bodies in vestibular (Scarpa’s) ganglion
  • have high firing rate
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16
Q

endolymph - relative motion

A
  • head moves to the right
  • canal moves in that direction
  • endolymph is fluid so it stays put by inertia
    differential movement
  • pushes cupula in that direction
17
Q

orientation of sterocilia - horizontal canal

A

I = inhibition
E = excitation

18
Q

each semicircular canal transduces

A

angular velocity in plane of duct

19
Q

there is no signal if movement is

A

normal to plane of duct

20
Q

if rotation is at an angle to plane of duct

A

signal is a vector fraction

21
Q

otolith organs structure

A
  • macula is a patch of hair cells
  • covered by gelatinous mass
  • otoconia embedded in mass
  • otoconia are CaCO3 crystals
22
Q

otolith organs orientation

A
  • located in saccule and utricle
  • utricular macula is horizontal
  • saccular macula is vertical
23
Q

otolith organ physiology

A
  • shearing forces act on otoconia
  • otoconial movements cause stereocilia to be deflected
24
Q

shearing forces are produced by

A
  1. linear acceleration or deceleration
  2. tilting of the head
25
Q

reflexes evoked by vestibular stimulation

A
  1. maintenance of equilibrium
  2. stabilization of visual orientation
26
Q

maintenance of equilibrium afferent fibers connect to

A

lateral vestibulospinal tract (extensor muscles of the eye)
- abducens, oculomotor, trochlear nuclei

27
Q

stabilization of visual orientaiton afferent fibers connect to

A

medial longitudinal fasciculus (MLF)
- this binds the 3 nuclei of eye movement

28
Q

vestibular afferents terminate in

A
  • vestibular nuclei (border between medulla and pons)
  • cerebellum
29
Q

vestibular nuclei

#? projects down what tract? CN?

A
  • 4 total (superior, lateral, inferior, medial)
  • lateral = projects down through spinal cord (LVST)
  • CN VIII distributes to all 4 nuclei
30
Q

vestibular nuclei efferents

A
  1. to abducens, trochlear, oculomotor nuclei via ascending MLF
  2. to neck motor neurons via descending MLF
  3. to limb and trunk motor neurons via LVST
  4. to cerebellum
  5. to reticular formation
  6. to VPM and cerebral cortex
31
Q

loss of vestibular function symptoms

A
  • difficulty maintaining balance
  • visual disturbances while walking
  • nystagmus
  • vertigo
  • nausea
32
Q

vestibular system disorders

A
  • Benign positional vertigo
  • meniere’s disease
  • acoustic neuroma
  • ototoxic drugs
  • trauma
33
Q

motion sickness occurs when

A

motion signals transmitted by the eyes, vestibular system, and proprioceptors are at a variance with one another or with what is expected from previous experience

34
Q

motion sickness evokes what?

A
  • autonomic reactions (nausea, vomiting, pallor, sweating, hypersalivation, stomach awareness)
  • drowsiness
  • fatigue
35
Q

continued exposure of motion sickness leads to

A

disappearance of reactions
- “sensory conflict and neural mismatch” theory

Dental Neuroscience (24 decks)

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