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NSCI 201 > Vestibular system > Flashcards

Vestibular system Flashcards

1
Q

True or false: the vestibular system does not have a dedicated primary area in the brain.

A

True.

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2
Q

With what liquid are the vestibular chambers filled with?

A

Endolymph.

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3
Q

What are the vestibular structures responsible for processing head tilts and linear acceleration? The vestibular structures responsible for processing rotations of the head?

A

Head tilts and linear acceleration:

  • Utricle
  • Saccule

Rotations of the head:

  • Anterior semicircular canal
  • Posterior semicircular canal
  • Lateral semicircular canal
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4
Q

What is the sensory receptor of the vestibular system?

A

The hair cells.

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5
Q

Where are located the hair cells in the vestibular system?

A

At the base of SC canals, in the ampullae.

In the utricle and saccule.

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6
Q

What is anatomically common for the ascending information of the auditory system and the vestibular system?

A

Vestibular nerve and cochlear nerve travel together as distinct divisions of the CN VIII.

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7
Q

Is the potential of hair cells in vestibular system biphasic or tonic?

A

Biphasic, like hair cells in the cochlea (intrinsic to its structure).

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8
Q

What are the hair cells polarities (orientations) in the different structures of the vestibular system?

A

Ampullae: single polarity
Saccule: bipolarity pointing outward
Utricle: bipolarity pointing inward

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9
Q

Where are found the otolith organs? What is their role? List three elements of their structure.

A

Located in:
-Utricle and saccule

Role:
-Provide sensibility to gravity (for head tilts and translational movements)

Structure:

  • Hair cells in otolith organs are contained in a sensory epithelium patch called maccula
  • Gelatinous layer sits on top of the maccula, the otolith membrane
  • On gelatinous layer sits otoconia, little crystals pulled by gravity
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10
Q

In the utricle and the saccule, what is the consequence of hair cells pointing either inward or outward on both sides of the striola?

A

Movement in one direction inhibits the population of hair cells on a side of the striola and excites the population of hair cells on the other side.

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11
Q

The saccules are oriented ____, responding to ____ head movements. The utricles are oriented ____, responding to ____ head movements.

Words to place:

vertical
horizontally
vertically
horizontal

A

The saccules are oriented vertically, responding to vertical head movements. The utricles are oriented horizontally, responding to horizontal head movements.

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12
Q

Concerning the firing rate, what distinguishes hair cells in the vestibular system to hair cells in the auditory system?

A

Vestibular hair cells have a resting firing rate, whereas cochlear hair cells don’t have one.

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13
Q

How many ampullae are there in total in one set of SC canals?

A

3

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14
Q

True or false: ampullae working together as a pair depolarize and hyperpolarize together.

A

False: depolarization in one ampulla results in hyperpolarization is the opposite corresponding ampulla.

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15
Q

What are the three pairs of SC canals? For what axis each is responsible for?

A

L-horizontal and R-horizontal : horizontal plane
L-anterior and R-posterior : LARP plane
R-anterior and L-posterior : RALP plane

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16
Q

Name two differences about the vestibular system compared to the other sensory modalities.

A
  • Multisensory (visual and somatosensory pathways)

- Has a motor function

17
Q

What is the obligatory passage in the central pathways of the vestibular system?

A

Vestibular nuclei (pons).

18
Q

What are the four pathways diverging from the vestibular nuclei?

A
  1. Vestibuloocular pathway
  2. Descending projections to spinal cord
  3. Vestibulo-cerebellar pathway
  4. Thalamus to cortex
19
Q

What is the role of the vestibuloocular pathway?

A

Generating eye movement reflexes to counter head movements so gaze can be fixated.

20
Q

Where are located the nuclei responsible for eye movements?

A

Brainstem.

21
Q

True or false: when fixating in a gaze, eye movements will go in the opposite direction of head movements.

A

True.

22
Q

What can arise from damage to VOR?

A

Oscillopsia.

23
Q

What can be used to assess the integrity of vestibular system?

A

Doll’s eye maneuver.

24
Q

What is the role of the descending projections to spinal cord from vestibular nuclei?

A

Guide postural adjustments of head and body.

25
Q

The descending projections to spinal cord from vestibular nuclei form two reflexes, what are they?

A

Vestibulocervical reflex and vestibulospinal reflex.

26
Q

What does indicate the few number of synapses between the vestibular nerves and the motor neurons?

A

Very fast pathway.

27
Q

What are the respective pathways of the vestibulocerebral and vestibulospinal reflexes? What are their respective roles?

A

Vestibulocerebral reflex pathway: SC canals ->medial vestibular nucleus ->medial longitudinal fasciculus -> upper cervical levels of spinal cord.
Vestibulocerebral reflex role: regulation of head position.

Vestibulospinal reflex pathway: otolith organs -> lateral vestibular nucleus -> lateral vestibulospinal tract ->ventral horn of spinal cord.
Vestibulospinal reflex role: mediation of balance and upright posture.

28
Q

What is the principle target of the vestibular portion of the vestibulocochlear nerve?

A

Cerebellum.

29
Q

From where are most descending projections for vestibular central pathways coming from?

A

Cerebellum.

30
Q

What is the main purpose of bidirectional vestibulo-cerebellar circuits?

A

Allow to modulate vestibular activity.

31
Q

What are the main roles of the cerebellum in its vestibular functions? What are the main structures responsible for each role?

A
  • Bring adaptive changes to VOR -> flocculus and paraflocculus (purkinje cells of the cerebellum modulating firing properties of vestibular system)
  • Distinguishing head tilts from translational movements ->nodulus and uvula (integrate information from otolith organs and SC canals)
  • Distinguishing passive movements from self generated movements ->rostral fastigial nucleus (receives inputs from cortex)
32
Q

Describe the vestibular pathway to the cortex.

A

Superior and lateral vestibular nuclei →ventral posterior nuclear complex of thalamus → cortex area 2v, cortex area 3a and parietoinsular vestibular cortex

33
Q

What is the role of each structure innervated by axons coming from the ventral posterior nuclear complex of the thalamus in the cortex?

A
  • Cortex area 2v: part of dorsal visual stream →help to localize head in space
  • Cortex area 3a: part of somatosensory cortex →integrate with proprioceptive information
  • Parietoinsular vestibular cortex: integrate head motion
34
Q

True or false: axons from CN VIII eventually project to primary vestibular cortex.

A

False, no such cortex exists.

NSCI 201 (14 decks)

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