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C1 Modules > Vestibular anatomy + physiology > Flashcards

Vestibular anatomy + physiology Flashcards

1
Q

What does the inner ear consist of?

A

Bony labyrinth, a system of passages making up 2 main functional parts

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2
Q

What are the 2 functional parts of bony labyrinth?

A
  1. Cochlea - dedicated to hearing

2. Vestibular system - dedicated to Balance

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3
Q

What can bony labyrinth be subdivided into?

A
  1. Vestibule
  2. 3 semicircular canal
  3. Cochlea
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4
Q

What are the pair of membranous sacs of vestibule?

A
  1. Saccule (Sacculus)

2. Utricle (Utriculus)

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5
Q

What do receptors in the vestibule provide for?

A

sensations of gravity and linear accelerations

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6
Q

What do semicircular canal enclose and what are receptors stimulated by?

A

Enclose slender semicircular duct

Receptors are stimulated by rotation of the head

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7
Q

What is The vestibular system comprised of ?

A

two types of sensors: the two otolith organs (the saccule and utricle), which sense linear acceleration (i.e., gravity and translational movements), and the three semicircular canals, which sense angular acceleration in three plane

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8
Q

What is sense of hearing provided by?

A

Receptors within cochlear duct

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9
Q

What are 2 sets of end organs in inner ear, or labyrinth?

A
  1. Semi circular canal

2. Utricle and saccule within vestibule

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10
Q

What is the function of semi circular canal?

A

Respond to rotational movement (angular head acceleration

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11
Q

What is the function of utricle and saccule within vestibule?

A

Respond to changes in the position of head with respect to gravity

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12
Q

What are inner ear function and symptoms?

A

Auditory - hearing loss, tinnitus, hyperacusis

Vestibular - dizziness, vertigo, unsteadiness, imbalance, falls, oscillopsia

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13
Q

What is oscillopsia?

A

Visual disturbance in which objects in the visual field appear to oscillate

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14
Q

What is hyperacusis?

A

Heightened sensitivity to particular sounds

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15
Q

What is the vestibular part of the inner ear?

A
  1. Saccule
  2. Utricle
  3. 3 semicircular canal [anterior, posterior, horizontal] with their ampullary tissue
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16
Q

What does Otolith sense?

A

sense linear head acceleration

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17
Q

How are the superior and posterior semicircular canal orientated?

A

Vertically at right angles to each other

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18
Q

Lateral semicircular canal

A

about 30-degree angle from the horizontal plane

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19
Q

What does orientation of the canal cause?

A

A different canal to be stimulated by movement of head in different planes

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20
Q

What does horizontal canal detect?

A

Angular acceleration of head when the head the head is turned

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21
Q

What do superior and posterior canal detect?

A

Vertical head movement when the head is moved up or down

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22
Q

What do each of 3 semicircular canal have at its base?

A

A bulbous expansion called ampulla which houses sensory epithelium or crista that contains hair cells

23
Q

What is semicircular canal?

A

three fluid-filled bony channels in the inner ear. They are situated at right angles to each other and provide information about orientation to the brain to help maintain balance.

24
Q

Where is capula located?

A

Within ampullae of each of the 3 semicircular canal

25
Q

What is capula?

A

Gelatinous component of crista ampullaris that extend from crista to the roof of ampullae

26
Q

What is the function of capula?

A

When the head rotates, the endolymph filling the semicircular duct initially lags behind due to inertia

The capula is deflected opposite direction od head movement

As endolymph pushes capula, the stereocilia is bent as well, stimulating hair cells within crista ampullaris

27
Q

Where does ampulla connect with?

A

utricle

28
Q

What happens when endolymph moves?

A

Pushes the gelatinous capula that covers crista ampullaris causes embedded hair cells to bend and send nerve impulses to the brain

29
Q

Lateral semicircular duct

A

Axial rotation

Fluid does not move in sync with labyrinth as a result of inertia

30
Q

Flexion and extension of the head

A

Anterior duct is most affected

31
Q

What are Type I + II vestibular hair cells defied by?

A

afferent innervation patterns

32
Q

What are the properties of type I hair cells?

A
  1. chalice cells
  2. one afferent nerve calyx
  3. '’true’’ receptors
    [90% afferents]
33
Q

What are the properties of Type II hair cells

A
  1. Cyclindrical cells
  2. Several afferent + efferent nerve endings
    [10% afferents]
  3. '’modulators’’
34
Q

What are 2 types of vestibular hairs?

A
  1. Kinocilium

2. Stereocilia

35
Q

What are the properties of kinocilium?

A

One, thicker and longer than stereocilia

Secured to cell by basal body

36
Q

What are the properties of stereocilia?

A

50-110 thin stereocilia/hair cells
Height increases across cell to kinocilium
Shorter in macula, in cristae up to 36 microns

37
Q

Deflection of hair bundle in the + direction?

A

Toward the longest stereocilia
Excitatory
The cell’s membrane is depolarised with respect to resting potential of about -60mv

38
Q

Displacement of hair bundle in - direction?

A

Inhibitory

Deflection in orthogonal direction produces no electrical response

39
Q

What provides maximal stimulus of vestibular stimulation?

A

A force parallel to the surface of sensory epithelium which bisects the bundle of stereocilia and passes directly through kinocilium

40
Q

What comes from utricle and saccule within vestibule?

A

The information for static equilibrium and linear acceleration

41
Q

What does saccule and utricle each contain?

A

A sense organ called macula, where stereocila + their supporting cells are formed

42
Q

What are 4 subnuclei of vestibular nucleus complex?

A
  1. Medial vestibular nucleus
  2. Lateral vestibular nucleus
  3. Inferior vestibular nucleus
  4. Superior vestibular nucleus
43
Q

What is vestibulo-ocular reflex

A

Responsible for maintaining eye fixation during head movement

Involves a 3 neuron arc

Obtain objects on fovea

VOR responds to head movement with eye movement that is equal in magnitude but opposite in direction

44
Q

What is vestibulo-ocular arc?

A

Neuron from semicircular canal
Neuron in the vestibular nuclei transmit information to eye muscle nuclei

eye motor neuron

45
Q

What is Head thrust test?

A

Tests the VOR

This reflex is helpful to maintain corrective eye position during any change in head position + to correct eye movement rapidly so that vision remains on target

46
Q

What is vestibulo-spinal reflex?

A

Coordinate head + neck movement with trunk + body, with the goal of maintaining head in upright position

47
Q

What is lateral vestibulospinal?

A

Postural changes to compensate for tilts and movements of body

48
Q

What is medial vestibulospinal?

A

Stabilizes head position during walking

49
Q

What is vestibulo-collic reflex?

A

Acts on neck musculature to stabilize the head with body movements

50
Q

What are the mechanisms of balance?

A
  1. Vision
  2. Cortex, cerebellum, reticular formation, extra-pyramidal system
  3. Cortical awareness of head/body/motion
  4. Cintrol of oculo-motor activity
  5. Control of posture
  6. Control od motor skills
  7. Labyrinthine activity
  8. Proprioception superificial sensation
51
Q

What is proprioception?

A

'’sense to self’’

Ability to sense movement within joints and joint angle, muscle length/tension

52
Q

The vestibulo cerebellum

A

Functions as an adaptive processor and re-adjust vestibular input through inhibition

Higher cortical level = most likely in/near parietal or insular cortex

53
Q

Ascending connection from vestibular nuclei

A

Anterior horn cells of spinal cord, via vestibulo-spinal tract

Cerebellum

Contralateral vestibular nuclei

Cranial nuclei III, IV, + VI

Pontine reticular formation

Temporal cortex

54
Q

Cerebral modification

A

Cerebral function responsible for modification + ability to supress vestibular reflexes

Involvement of parietal cortex + ocular gyrus to visually suppress VOR

C1 Modules (20 decks)

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