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Neuro 2 > Vestibular Anatomy > Flashcards

Vestibular Anatomy Flashcards

1
Q

what are the roles of the vestibular system?

A
  1. estimate body position and movement
  2. postural control
  3. control of eye movements
  4. autonomic function and consciousness
  5. project info throughout cortex, brainstem and cerebellum
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2
Q

define pitch

A

rotation around y-axis

nodding yes

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3
Q

define yaw

A

rotation around the z-axis

shaking head no

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4
Q

define roll

A

rotation around the x-axis

tilting head side to side

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5
Q

what structures are included in the central vestibular system?

A
  1. vestibular nuclei (4)
  2. vestibular tracts (6)
  3. vestibulocerebellum
  4. vetibular cortex
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6
Q

what structures are included in the peripheral vestibular system?

A
  1. vestibular apparatus
    1. bony labyrinth
    2. otolith organs
    3. semi-circular canals
  2. CN 8 - vestibular branch
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7
Q

what are the primary functions of the peripheral vestibular system?

A
  1. stabilize visual images on fovea of the retina during head movement allowing for clear vision
  2. maintain postural stability (especially during movement of head)
  3. provide info for spatial orientation
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8
Q

the peripheral vestibular system is mainly responsible for ______________

A

relaying info (velocity and acceleration of the head)

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9
Q

what is included in the vestibular apparatus?

A
  1. bony labyrinth
  2. membranous labyrinth
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10
Q

what structures make up the membranous labyrinth?

A
  1. Vestibule
    • Otolith organs (utricle and saccule)
  2. Semicircular canals
    • anterior canal
    • posterior canal
    • horizontal canal
  3. Cochlea
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11
Q

what is the role of the otolith organs?

A

linear acceleration/deceleration

static head position

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12
Q

what is the role of the utricle and saccule?

A
  1. Utricle → detects movement in the horizontal plane
  2. Saccule → detects movement in the verticle plane
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13
Q

what are stereocilia?

A
  • gravity-dependent motion sensitivity
  • hair cells encased in gelatinous layer (macula)
  • layered on top: Otoconia
    • calcium carbonate crystals
    • heavier than structures it overlays
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14
Q

describe how stereocilia work

A
  • Motion receptors → transduce minute displacements into behaviorally relevant potentials
    • movement of stereocilia towards kinocilium = excitatory
    • movement of stereocilia away from kinocilium = inhibitory
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15
Q

how do the semicircular canals function?

A

they are encased in the bony labyrinth and filled with endolymph

  • head rotation → movement of endolymph in corresponding canal → movement of hair cells → depolarization/hyperpolorization
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16
Q

what are ampulla?

A

bulbous formation at the start or finish of each canal

contains cupula, which houses stereocillia

which are sensitive to angular movements only

17
Q

hair cell displacement towards the utricle is called _______

A

utriculopedal cupular displacement

18
Q

hair cell displacement away from the utricle is called _________

A

utriculofugal cupular displacement

19
Q

utriculopedal cupular displacement is excitatory/inhibitory for what?

A
  1. Excitatory → horizontal canall
  2. Inhibitory → anterior/posterior canal
20
Q

utriculofugal cupular displacement is excitatory/inhibitory for what?

A
  1. excitatory → anterior/posterior canal
  2. inhibitory → horizontal canal
21
Q

list and briefly describe the vestibular reflexes

A
  1. Vestibulo-Ocular Reflex (VOR)
    • stable vision during head motion
  2. Vestibulo-Spinal Reflex (VSR)
    • stable body during head motion
  3. Vestibulo-Collic Reflex (VCR)
    • stable neck during head motion
22
Q

Describe VOR connections to ocular nuclei

A

labyrinth → vestibular nuclei → ascending tracts (cross at MLF) → ocular motor nuclei (III, IV, VI)

excite/inhibit the agonist/antagonist muscles needed to move the eyes in the desired direction

23
Q

describe what occurs within the horizontal canals when turning the head to the left

A
  • left horizontal semicircular canal → the endolymph is pushed towards the utricle → utriculocupular displacement = excites horizontal canal
  • right horizontal semicircular canal → the endolymph is displaced away from utricle → utriculofugal displacement = inhibits horizontal canal
24
Q

what is the purpose of the VSR?

A

generation of compensatory body movements to maintain head and postural stability

25
Q

list the steps involved in the VSR

A
  1. head tilts to side
  2. ipsilateral SCC/otoliths excitation
  3. increased input from vestibular nerve → vestibular nuclei ipsilaterally
  4. MVST/LVST descending drive to truncal muscles
  5. increased truncal extension ipsilaterally and increased truncal flexion contralaterally
26
Q

what is the purpose of the VCR?

A

similar to VSR only works on the cervical musculature

it counters a movement sensed by our labyrinth otolithic or SCC and modulates neck movements accordingly to help with postural stability

27
Q

list the cervical reflexes

A
  1. Cervico-ocular reflex (COR)
  2. Cervicospinal reflex (CSR)
  3. Cervicocollic reflex (CCR)
28
Q

describe the COR

A
  • interacts closely with VOR
    • can supplement VOR under certain circumstances
  • eye movements driven by neck proprioceptors
29
Q

describe the CSR

A
  • changes in limb position driven by neck afferent activity
    • can supplement VSR under certain circumstances
30
Q

describe the CCR

A
  • helps stabilize head on body
    • afferent input caused by changes in neck position (stretch) → contralateral reflexive contraction of appropriate neck muscles
31
Q

what structures are involved in the central vestibular system?

A
  1. Vestibular nuclei
    • Lateral/Medial nucleus
    • Superior/Inferior nucleus
  2. Vestibular tracts
    • Medial/Lateral vestibulospinal
    • vestibulocerebellar
  3. Vestibulocerebellum
  4. Vestibular Cortex
32
Q

what are the functions/relay points of the vestibular nuclei?

A
  1. eye movement control for gaze stability during movment (oculomotor)
  2. postural control and movement (brainstem)
    • aid in maintaining tone
  3. spatial orientation (cortex)
  4. autonomic nervous system control
33
Q

describe the lateral vestibulospinal tract

A

travels to the thoracic spinal cord to extensor muscles

  • head and body position in space
  • walking upright
  • righting and equilibrium reactions
34
Q

describe the medial vestibulospinal tract

A

travels bilaterally to the MLF to the cervical cord to extensor muscles

  • head movements
  • integrating head and eye movements
35
Q

what is the role of the vestibulocerebellum?

A

responsible for postural and gaze stabilization

  • modulating VOR
  • VOR suppression/cancellation
  • VSR suppression/cancellation
36
Q

how is the thalamus involved in vestibular function?

A
  1. VPL of thalamus connects subcortical structures to the vestibular cortex
    • connection w/vestibular cortex and reticular formation for arousal and conscious awareness of body
  2. specific vestibular info processed in VPL
37
Q

what specific vestibular info is processed in the VPL?

A
  1. discrimination between self movement vs. that of environment
  2. spatial awareness and perceived vertical
  3. “personal space”
38
Q

List cortical regions involved in the Vestibular Cortex

A
  1. PIVC (parieto-insular vestibular cortex)
    • junction between parietal and insular lobe
    • thalamus connects it to cerebellum and vestibular nuclei
  2. Medial superior temporal region
    • visuo-vestibular integration
    • self-motion perception
  3. Ventral Intraparietal region
    • multisensory spatial coding
    • proprioception, auditory, visual, tactile, vestibular
39
Q

How is the vestibular system involved in autonomic function?

A

it has many projections throughout the brainstem to the reticular formation and other regions involved in autonomic function

Neuro 2 (29 decks)

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