Vestibular Anatomy and Overview Flashcards

1
Q

What is the primary function of the vestibular system?

A

Awareness of body position in space, maintaining postural control, and coordinating eye and head movements.

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2
Q

Where is the vestibular system located?

A

Deep in bilateral temporal bones with both peripheral and central components.

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3
Q

What are the three main functions of the vestibular system?

A
  • Gaze stability
  • Postural stability
  • Orientation in space
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4
Q

What reflex is responsible for maintaining clear vision while the head is in motion?

A

Vestibulo-Ocular Reflex (VOR): Generates eye movements which enable clear vision while head is in motion

  • Gaze stability
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5
Q

What reflex helps maintain balance during head movements?

A

Vestibulo-Spinal Reflex (VSR).

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6
Q

What are the two main components of the peripheral vestibular system?

A
  • the cochlea
  • the vestibular apparatus
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7
Q

What structures make up the vestibular apparatus?

(5)

A
  • Three semicircular canals
  • Two otolith organs (utricle and saccule)
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8
Q

What do the semicircular canals detect?

A

Angular acceleration of the head.

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9
Q

What do the otolith organs detect?

A

Utricle

  • Sits in a horizontal plane
  • Responds to horizontal linear acceleration and/or lateral head tilt

Saccule:

  • Sits in a vertical plane
  • Responds to vertical linear acceleration (Eg. Detecting up/down movement in an elevator)

  • Linear acceleration and static head tilt.
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10
Q

Which semicircular canal detects head rotation with forward motion?

A

Anterior (superior) canal.

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11
Q

Which semicircular canal detects posterior rotation of the head?

A

Posterior (inferior) canal.

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12
Q

Which semicircular canal detects lateral rotation of the head?

A

Horizontal (lateral) canal.

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13
Q

What is the function of endolymph in the semicircular canals?

A

It moves in response to head rotation, causing deflection of the cupula and hair cells.

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14
Q

Where are the sensory hair cells located within the semicircular canals?

A

In the ampulla, embedded in the gelatinous cupula.

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15
Q

What happens when the hair cells in the semicircular canals are deflected?

A

An action potential is generated, sending excitatory or inhibitory signals via the vestibular nerve.

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16
Q

What are the ‘functional pairs’ in the semicircular canals?

A

Coplanar pairs where one canal increases signals while the partner decreases signals.

  • R/L horizontal canals are a functional, coplanar pair
  • LARP”= Left anterior/right posterior make acoplanar pair
  • RALP”= Right anterior/Left posterior make a coplanar pair
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17
Q

.

A

.

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18
Q

What results from an acute disturbance in the semicircular canals?

A

Vertigo and imbalance.

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19
Q

Which otolith organ senses horizontal linear acceleration?

A

Utricle.

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20
Q

Which otolith organ senses vertical linear acceleration?

A

Saccule.

21
Q

What is the function of the otoconia in the otolith organs?

A

They act as ballast, accentuating the bending of hair cells during head movement.

22
Q

What can happen if otoconia become displaced into the semicircular canals?

A

It can lead to Benign Paroxysmal Positional Vertigo (BPPV).

23
Q

Where is the information from the SCCs and otoliths sent?

A

To the cerebellum and vestibular nuclei in the brainstem via CNVIII.

24
Q

How many vestibular nuclei are there on each side of the brainstem?

A

Four.

25
Q

What role does the cerebellum play in the vestibular system?

A

It helps with the smoothness of movement by processing vestibular input.

26
Q

What does the vestibulospinal tract help maintain?

A

Postural stability.

27
Q

To which cranial nerves does the vestibular system send information to coordinate eye movements?

A
  • CN III
  • CN IV
  • CN VI
28
Q

What is the role of the tonic firing rate in the vestibular nerve?

A

It allows detection of head motion through changes in firing rate.

29
Q

What happens when there is an asymmetry in tonic firing rate between the vestibular nerves?

A

It leads to vertigo and nystagmus.

30
Q

What is the VOR phase?

A

As the head moves in one direction, the eyes move in the opposite direction with equal amplitude.

31
Q

What is the VOR gain?

A

The ratio of eye velocity to head velocity, ideally 1:1.

32
Q

What are the consequences of VOR dysfunction?

A

Difficulty with fast head movements, dizziness, nausea, and blurry vision with head movement.

33
Q

What is oscillopsia?

A

Blurry or bouncy vision with head movement due to decreased gaze stability.

34
Q

What are the primary functions of the central vestibular system?

(2)

A

Integration of sensory information and coordination of motor output.

35
Q

What is the role of the medial and lateral vestibulospinal tracts?

A

They help maintain postural stability (VSR).

36
Q

.

A

.

37
Q

What might result from damage to the central vestibular system?

A

Impaired coordination, dizziness, and balance issues.

38
Q

.

A

.

39
Q

What is the function of the vestibular nucleus complex?

A

Integration of sensory input from vestibular, visual, and somatosensory systems.

40
Q

Which sensory systems are involved in maintaining equilibrium?

A
  • vestibular system
  • visual system
  • somatosensory system
41
Q

What are the three components of motor output in the vestibular system?

A
  • Eye movements (VOR)
  • Postural movements (VSR)
  • Head movements
42
Q

What can cause vertigo?

A

Acute disturbances in the semicircular canals or otolith organs.

43
Q

How does the brain detect the direction of head movement?

A

By comparing the input from the partner coplanar receptors in the semicircular canals.

44
Q

.

A

.

45
Q

What is BPPV?

A

Benign Paroxysmal Positional Vertigo, a condition caused by displaced otoconia.

46
Q

How do the semicircular canals detect angular acceleration?

A

Through the movement of endolymph and deflection of the cupula.

47
Q

.

A

.

48
Q

What is the significance of coplanar pairs in the semicircular canals?

A

They allow the brain to detect the direction and speed of head movement accurately.

49
Q

What is the result of non-reciprocal signals between coplanar pairs?

A
  • abnormal eye movements
  • balance issues
  • dizziness
  • vertigo