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Neuroscience I Exam #3 > The Vestibular System > Flashcards

The Vestibular System Flashcards

1
Q

Peripheral receptor apparatus

A

In inner ear, responsible for transducing head motion/position

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2
Q

Central vestibular nuclei

A

Integrating and distributing info that controls motor activities and spatial orientation.

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3
Q

Vestibuloocular network

A

Involved in the control of eye movements. Keeps eyes fixed when looking at an objetc.

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4
Q

Vestibulospinal network

A

Coordinates head movements, axial ms., and postural reflexes

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5
Q

Vestibulothalamocortical network

A

Conscious perception of movement/spatial orientation

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6
Q

Perilymph

A

Between spaces of membranous and bony labyrinths.

Similar to CSF.

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7
Q

Endolymph

A

Fills membranous labyrinth.

Covers sensory receptors of auditory and vestibular systems.

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8
Q

Semicircular canals detect:

Otolith organs detect:

A

Rotational head movements.

Translational head movements.

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9
Q

Cells from vestibular organs are innervated by primary afferent fibers from:

A

Vestibular ganglion

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10
Q

Blood supply to vestibular system

A

Labyrinthine a. (from AICA)

Stylomastoid a. (mainly to semicircular canals)

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11
Q

Disruption of BS to labyrinth can cause:

A

Vertigo sx, nystagmus, unstable gait.

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12
Q

How are receptors in utricle oriented?’

In saccule?

A

Longitudinally along base of utricle, and vertically within saccule (along medial wall).

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13
Q

Endolymph in labyrinth is drained into:

A

Endolymphatic sinus

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14
Q

Ductus reuniens

A

Connects saccule to cochlea

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15
Q

Meniere’s disease cause:

Sx:

TTM:

A

Causes by disruption of normal endolymph volume, causing abnormal distension of membranous labyrinth.

Sx: occasional hearing loss, vertigo, nystagmus, nausea.

TTM: diuretics, low salt diet.

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16
Q

Hair cells w/ stereocilia project from:

What’s kinocilium?

A

Apical surface.

Longer single layer of stereocilia.

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17
Q

Type I cells

A

Goblet shaped cells surrounded by nerve calyx.

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18
Q

Type II cells

A

Cylindrical and innervated by synaptic buttons.

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19
Q

What do the hair cells receive?

A

Synapses from vestibular efferent that control receptor sensitivity.

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20
Q

Where do hair cells sit?

A

Within the crista in the ampulla

21
Q

Where do the stereocilia of hair cells extend into?

A

Otolith membrane.

22
Q

Otoconia

Function?

A

Calcium carbonate crystals that cover otolith membrane.

Change in head position relative to gravity/linear accelerations and bends underlying hair cell stereocilia.

23
Q

4 vestibular nuclei

A

Superior vestibular nucleus
Medial vestibular nucleus
Lateral vestibular nucleus
Inferior vestibular nucleus

24
Q

How do primary afferent fibers enter the midbrain to target the vestibular nuclei?

A

They enter from CN VIII at pontomedullary junction and go thru restiform body (ICP) and synapse in one of the nuclei.

25
Q

Primary vestibulocerebellar fibers

A

Course through juxtrarestiform body (ICP) to send collaterals to dentate nucleus and terminate on mossy fibers.

26
Q

What are secondary vestibulocerebellar projections?

A

Fibers from vestibular nuclei to fastigial and dentate nuclei.

27
Q

Vestibulovestibular fibers

A

Exist from all nuclei. Form reciprocal connections w/ analogous contralateral nucleus.

28
Q

Spinovestibular fibers

A

From all levels of the SC.

Provide proprioceptive input to medial and lateral vestibular nuclei.

29
Q

Rotational vestibuloocular reflex (4)

A
  1. Primary afferents from horizontal semicircular canals project to specific neurons in medial and lateral vestibular nuclei.
  2. Axons are sent through the medial longitudinal fasciculus (MLF) to CL abducens nucleus.
  3. Abducens n. activate lateral rectus m.
  4. Abducens interneurons send excitatory impulses to oculomotor nucleus to innervate medial rectus m.
30
Q

When head turns left, what is the rotational vestibuloocular reflex? (4)

A
  1. Left horizontal semicircular canal activates neurons in left vestibular nuclei.
  2. Inhibitory signals from right vestibular nuclei are decreased by commissural neurons.
  3. Neurons in left vestibular nuclei excite CL abducens motor neuron.
  4. Contraction of right lateral rectus m. and left medial rectus m.
31
Q

Linear vestibuloocular reflex is a similar pathway to:

A

Rotational vestibuloocular reflex.

It is activated to keep eyes fixes when head is moving (jogging, stabilize gait, etc).

32
Q

Slow phase and fast phase of nystagmus

A

Slow phase is when the vestibuloocular reflex directs eyes slowly opposite head movement.

Fast phase is the rapid springing back of eyes to center, then another slow phase begins.

33
Q

Caloric test

A

Used for patients complaining of dizziness, vertigo, etc.

Warm or cold water introduced into ear.

Warm water causes nystagmus toward ear that water is introduced. Cold water causes nystagmus toward opposite ear.

COWS

34
Q

UL lesion of vestibular pathway will result in what kind of nystagmus on caloric test?

A

Reduced or absent nystagmus IL on caloric test.

35
Q

Lateral vestibulospinal tract (LVST)

A
  1. Neurons in lateral and inferior vestibular nuclei project IL to anterorostral areas (cervical cord) or posterocaudal areas (lumbosacral cord).
  2. Fibers course through brainstem (lateral medulla and anterior funiculus of SC) to terminate on motoneurons in laminae VII to IX.
  3. Collaterals given off at different segments ensuring coordination of posture.
36
Q

Medial vestibulospinal tract (MVST)

A

Functions to stabilize the neck ms.

Neurons from medial vestibular nucleus descend BL thru MLF and terminate in laminae VII to IX of cervical SC.

37
Q

Vestibular thalamus have neurons that project:

What parts of thalamus?

A

Neurons from all vestibular nuclei project BL here, but mostly CL.

VPL and VPI.

38
Q

Areas 2v and 3a (primary somatosensory cortex)

A

2v produces sensation of whole body motion.

3a integrates motor control of head and body.

39
Q

Area 7

A

Houses neurons involved in spatial coding, visual and vestibular motion signals.
Integrates cues of body motion in space.

40
Q

Lesions of area 7 cause:

A

Confusion in spatial awareness

41
Q

Insular areas of lateral sulcus and PIVC

A

Cells respond to body motion, somatosensory, proprioceptive and visual motion stimuli.

42
Q

Lesions of PIVC cause:

A

Episodes of vertigo, unsteadiness, loss of perception for “visual vertical”.

43
Q

Prefrontal cortex and superior frontal gyrus

A

Controls rapid movement eye (saccades) and smooth eye movements.

44
Q

Subjective vs. objective vertigo

A

Subjective: patient experiences the sensation of spinning while environment is still.

Objective: environment is spinning while patient is still.

45
Q

Benign paroxysmal positional vertigo

A

Brief episodes of vertigo from changes in body position.

Thought to be caused by otoconial crystals that get lodged in cupula of semicircular canal (cupulolithiasis).

46
Q

Vestibular Schwannoma
Cause:
Sx:

A

Benign tumor from Schwann cells.
Can impinge CN VII, CN VIII and labyrinthine a.
Can cause hearing loss, gait problems, tinnitus.

47
Q

Vestibular neuritis

A

Usually occurs post infection.

Patients present w/ severe vertigo, nausea, vomiting, but no hearing loss or CNS defects.

48
Q

Anterorostal area in LVST

Posterocaudal area in LVST

A

AR - go to cervical levels.

PC - go to lumbar, trunk, etc. levels.

Neuroscience I Exam #3 (14 decks)

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