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C1 Modules > Vestibular anatomy + physiology > Flashcards

Vestibular anatomy + physiology Flashcards

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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?

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A

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

23
Q

What is semicircular canal?

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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?

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A

Within ampullae of each of the 3 semicircular canal

25
What is capula?
Gelatinous component of crista ampullaris that extend from crista to the roof of ampullae
26
What is the function of capula?
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
Where does ampulla connect with?
utricle
28
What happens when endolymph moves?
Pushes the gelatinous capula that covers crista ampullaris causes embedded hair cells to bend and send nerve impulses to the brain
29
Lateral semicircular duct
Axial rotation | Fluid does not move in sync with labyrinth as a result of inertia
30
Flexion and extension of the head
Anterior duct is most affected
31
What are Type I + II vestibular hair cells defied by?
afferent innervation patterns
32
What are the properties of type I hair cells?
1. chalice cells 2. one afferent nerve calyx 3. ''true'' receptors [90% afferents]
33
What are the properties of Type II hair cells
1. Cyclindrical cells 2. Several afferent + efferent nerve endings [10% afferents] 3. ''modulators''
34
What are 2 types of vestibular hairs?
1. Kinocilium | 2. Stereocilia
35
What are the properties of kinocilium?
One, thicker and longer than stereocilia | Secured to cell by basal body
36
What are the properties of stereocilia?
50-110 thin stereocilia/hair cells Height increases across cell to kinocilium Shorter in macula, in cristae up to 36 microns
37
Deflection of hair bundle in the + direction?
Toward the longest stereocilia Excitatory The cell's membrane is depolarised with respect to resting potential of about -60mv
38
Displacement of hair bundle in - direction?
Inhibitory | Deflection in orthogonal direction produces no electrical response
39
What provides maximal stimulus of vestibular stimulation?
A force parallel to the surface of sensory epithelium which bisects the bundle of stereocilia and passes directly through kinocilium
40
What comes from utricle and saccule within vestibule?
The information for static equilibrium and linear acceleration
41
What does saccule and utricle each contain?
A sense organ called macula, where stereocila + their supporting cells are formed
42
What are 4 subnuclei of vestibular nucleus complex?
1. Medial vestibular nucleus 2. Lateral vestibular nucleus 3. Inferior vestibular nucleus 4. Superior vestibular nucleus
43
What is vestibulo-ocular reflex
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
What is vestibulo-ocular arc?
Neuron from semicircular canal Neuron in the vestibular nuclei transmit information to eye muscle nuclei eye motor neuron
45
What is Head thrust test?
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
What is vestibulo-spinal reflex?
Coordinate head + neck movement with trunk + body, with the goal of maintaining head in upright position
47
What is lateral vestibulospinal?
Postural changes to compensate for tilts and movements of body
48
What is medial vestibulospinal?
Stabilizes head position during walking
49
What is vestibulo-collic reflex?
Acts on neck musculature to stabilize the head with body movements
50
What are the mechanisms of balance?
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
What is proprioception?
''sense to self'' Ability to sense movement within joints and joint angle, muscle length/tension
52
The vestibulo cerebellum
Functions as an adaptive processor and re-adjust vestibular input through inhibition Higher cortical level = most likely in/near parietal or insular cortex
53
Ascending connection from vestibular nuclei
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
Cerebral modification
Cerebral function responsible for modification + ability to supress vestibular reflexes Involvement of parietal cortex + ocular gyrus to visually suppress VOR

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