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LCRS 2 > Vestibular Systems > Flashcards

Vestibular Systems Flashcards

1
Q

Which structures in the body are responsible for angular (rotational) motion of the head?

A

Semi-circular canals

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2
Q

Which structures in the body sense the acceleration of the head and the strength of gravity?

A

Otolith organs

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3
Q

What are the two otolith organs?

A

Saccule

Utricle

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4
Q

Define vertigo.

A

False perception of movement in space

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5
Q

Define vestibular ataxia

A

Instability of gait or posture

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6
Q

What are some other consequences of vestibular loss?

A

Slight impairment of orthostatic control
Severe nausea and vomiting
Loss of coordination on directional reorientation, motion intolerance, oversensitivity to visual motion in the environment

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7
Q

What type of cell is involved in the detection of movement in the vestibular system?

A

Hair cells

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8
Q

Describe the cilia of these hair cells.

A

There is one kinocilium and the rest are stereocilia

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9
Q

What does the hair cell fibre synapse with and where does it project?

A

It synapses with a primary neurone dendrite (cell body in Scarpa’s ganglion)
They project to the vestibular nuclei in the brainstem

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10
Q

What stimulates hair cells?

A

In Otoliths: deflection by forces of inertial resistance to acceleration
In Semi-circular Canals: endolymphatic fluid rotation

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11
Q

Describe how the hair cell receptor potential can be changed.

A 
Depolarisation = movement towards the kinocilium 
Hyperpolarisation = movement away from the kinocilium
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12
Q

Describe how ganglion cell discharge can be changed.

A

Towards the kinocilium = increased firing frequency

Away from the kinocilium = decreased firing frequency

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13
Q

Describe the orientation and sensitivities of the saccule.

A

Saccule is oriented vertically with the hair cells projecting normal to the plane
They are sensitive in all combinations of vertical and antero-posterior directions

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14
Q

Describe the orientation and sensitivities of the utricle.

A

Utricle is oriented almost horizontally with the hair cells projecting vertically
Directional sensitivities in all combinations of lateral and antero-posterior directions

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15
Q

Describe the structure and function of the semi-circular canals.

A

Hair cells project from the ampulla in the wall of the canal and are uni-directionally oriented so that acceleration to a particular side stimulates the canals on that side (e.g. rotation of the head to the right stimulates the right canal, rotation in the other direction inhibits the right canal activity)
When head rotation decelerates to a stop, the canal on the other side (left side) is stimulated

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16
Q

Describe the firing of the canals when the head is still.

A

Each canal has a tonic firing rate so that they equal out when the head is still

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17
Q

What are the effects of loss of canal function on one side?

A

There is unopposed signal coming from the intact side meaning that there is partial impairment of sensitivity to rotation in the ‘on’ direction of the defunct canal

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18
Q

Why would a unilateral canal lesion cause vertigo?

A

The unopposed tonus of the intact canal gives a signal as if the head is rotating to the intact side.
Patient may feel like they’re spinning even though they’re not.

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19
Q

Why would acute unilateral vestibular disorder cause vestibular nystagmus?

A

Unopposed tonus of the intact canal causes the eyes to be driven to the lesioned side – this is a vestibulo-ocular reflex (because it thinks that your head is rotating towards the intact side)

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20
Q

Where do superior and medial vestibular neurones project?

A

They project to the motor nuclei supplying extraocular muscles.

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21
Q

Describe the path of medial vestibular neurones.

A

The axons of medial vestibular neurones cross the midline and project to the contralateral abducens (VI) nucleus to abduct the eye on the opposite side (in the opposite direction to head rotation)
Axons from the abducens nucleus ascend in the MLF to the contralateral oculomotor nucleus (III) to adduct the other eye (in theopposite direction to head rotation)

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22
Q

Describe the path of superior vestibular neurones.

A

Project ipsilaterally to the oculomotor and trochlear nuclei to generate
VERTICAL vestibulo-occular reflexes

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23
Q

What is oscillopsia?

A

Everything appears to be oscillating
This is due to marked loss of vestibular function impairing eye stabilisation during rapid head movements.
The vestibulo-ocular reflex is lost.

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24
Q

How would you test if a patient has oscillopsia?

A

Tell the subject to look at a fixed target and then rapidly move their head.
If they have bilateral loss of vestibular function then their eyes will be taken off target by the head swing.

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25
Q

What are the effects of bilateral vestibular disorder on gait?

A

Mild gait ataxia

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26
Q

What are the effects of unilateral vestibular disorder on gait?

A

Tendency for the body and head to lean or fall to the lesioned side

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27
Q

Describe the path and function of the lateral vestibulo-spinal tract.

A

Descends ipsilaterally in the ventral funiculus of the spinal cord
Axons terminate in lateral part of ventral horn Influence motor neurones to limb muscles

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28
Q

Describe the path and function of the medial vestibulo-spinal tract.

A

Descend bilaterally in MLF to cervical and upper thoracic spinal cord
Axons terminate in medial part of ventral horn
Influence motor neurones to back and neck muscles

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29
Q

State a common cause of vestibular vertigo that lasts:

a. Seconds
b. Minutes
c. Hours
d. Days
e. Fluctuating/continuous
f. Silent

A 
a. Seconds 
Benign Paroxysmal Positional Vertigo (BPPV)
b. Minutes 
Vertebrobasilar insufficiency
c. Hours 
Meniere’s Syndrome 
d. Days 
Vestibular neuritis 
e. Fluctuating/continuous  
Uncompensated vestibular lesion 
f. Silent 
Acoustic neuroma
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30
Q

Inputs to vestibular system

A

Vision
Pressure in feet
Inner ear for info on rotation and gravity

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31
Q

Outputs of vestibular system

A

Ocular reflex

Posture control

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32
Q

What bone is inner ear in

A

Petrus part of temporal as hardest

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33
Q

How many organs to vestibular system per ear

A

5

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34
Q

Otilith organs of vestibular system

A

Sacculus

Utricals

35
Q

What does sacculus connect to

A

Superiorly utricle and inferiorly cochlea

36
Q

What are 3 other organs to system

A

Lateral
Posterior
Superior canals

37
Q

What do 3 canals connect to

A

Utricle

38
Q

What fluid is in vestibular organs

A

Endolymph

39
Q

What fluid is between organ and bone

A

Perilymph

40
Q

What do each semi circular canals have

A

They have 2 canals leading to utricle

For each defined canal there is one wide and one narrow canal

41
Q

What is name given to wider canals

A

Ampulla

42
Q

Comparison of anterior and posterior canal planes

A

90 degrees

Purposefully orientated

43
Q

Types of hair cells in vestibular organ

A

Type 1 and 2

44
Q

Differences between type 1 and 2

A

More of type 1
Type 1 has indirect efferent but type 2 has direct
Afferents all direct

45
Q

Where are hair cells in sacula

A

Side part nearest cochlea

46
Q

Where are hair cells in utricle

A

At bottom

47
Q

What plane does utricle deal with

A

Horizontal

48
Q

What plane does sacula deal with

A

Vertical

49
Q

What are otoliths

A

Carbonate cristals

50
Q

Name given to functional component of otoliths

A

Maculae

51
Q

Components of maculae

A

Hair cells
Gelatinous matrix
Otoliths

52
Q

Where is gelatinous matrix

A

On top of hair cells

53
Q

Purpose of gelatinous matrix

A

AIDS hair cell movement

54
Q

Where are otoliths

A

On matrix

55
Q

How are hairs stimulated

A

If moved in one way they trigger stimulatory pathway and in other an inhibitory pathway

56
Q

What is striola

A

Central part of maculae

Either side of it the orientation of cilia in opposite direction

57
Q

Where are hair cells in semicircular canals

A

Ampulla

58
Q

Where is cupula

A

Ampulla

59
Q

What is the cupula

A

A gelatinous mixture more dense than endolymph

60
Q

Direction of hair cells in ampulla

A

All in one direction unlike otoliths

Mirroring instead occurs between ears

61
Q

Name of functional part of ampulla

A

Crista

62
Q

Supply of blood to vestibular system in inner ear

A

Basilar artery-> anterior inferior cerebrellar artery -> labyrinthine

63
Q

Divisions of vestibular nerve

A

Inferior and superior

64
Q

Where does vestibular nerve go

A

Vestibular nuclei

65
Q

Organisation of vestibular nuclei

A

Lateral and inferior deal with static labyrinth

Medial and superior deal with kinetic labyrinth

66
Q

Where do vestibular nuclei project

A

Spinal chord
Cerebellum
Nuclei of extraocular muscles
Cardiovascular and respiratory centres

67
Q

Tracts for vestibulospinal reflexes and place innervated

A

Medial vestibulospinal tract- upper back and neck

Lateral vestibulospinal tract- limbs and trunk

68
Q

Vestibulocerebrellar reflex goes where and via what

A

Vestibulo cerebellum via inferior cerebrellar peduncle

69
Q

Where does vestibulo-ocular reflex travel to and via what

A

Oculumotor, abducens and trochlear nucleus via medial longtitudal fasiculus

70
Q

Route from vestibular nuclei to vestibular cortex

A

Medial leminiscus to ventroposterior nucleus to vestibular cortex via internal capsule

71
Q

Physiology of hair cell potentials

A

Tips open k+ channels depolarising the cell, leads to ca2+ influx which binds to vesicles

72
Q

Resting discharge of hair cells

A

Tonic activity of hair cells
If excited then more frequent impulses due to depolarisation
If inhibited then less frequent impulses due to hyperpolarisation
Same applies to ones in cochlea

73
Q

Effect of acceleration on hair cells

A

Acceleration causes hairs to shift in opposite direction to acceleration as endolymph moves gelatinous matrix

74
Q

How semicircular canals work between ears

A

They are paired

75
Q

Pairings of left and right semicircular canals

A

Lateral both together
Left anterior and right posterior
Right anterior and left posterior

LARP and RALP

76
Q

Way of remembering parings

A

Ralp and Larp

77
Q

Lateral vestibulospinal pathway

A

Lateral vestibular nucleus down lateral vestibulospinal tract to influence ipsilateral limb movements

78
Q

Medial vestibulospinal tract pathway

A

From medial vestibular nucleus down medial vestibular tract to upper thoracic and cervical levels as supplies trunk and neck muscles

79
Q

Differences between lateral and medial vestibulospinal pathways

A

Medial is bilateral (ipsilateral pathway more dense)

80
Q

Purpose of having hairs in 2 directions

A

Can send same signal twice but in different way

One being that the hairs have been stimulated and other being that they have been inhibited

81
Q

Vestibuloocular reflex features

A

Aims to keep image fixed so ensure eye movements in opposite direction to head movement
Fastest reflex in the body

82
Q

Vestibulo ocular pathway horizontal

A

Lateral SCC-> scarpas ganglion->vestibular nucleus-> abducens nucleus-> up medial longtitudal fusiculus-> occulomotor nucleus-> lateral and medial rectus

83
Q

Vestibulo ocular pathway vertical

A

Anterior SCC-> scarpas ganglion->vestibular nucleus-> abducens nucleus-> up medial longtitudal fusiculus-> occulomotor nucleus-> superior oblique

84
Q

Common symptoms of vestibular issues

A

Vertigo
Dizziness
Unsteadiness
Issues of movement perception

LCRS 2 (44 decks)

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