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The Nervous System: Physiology > Vestibular System > Flashcards

Vestibular System Flashcards

1
Q

What is the overall function of the Vestibular system

A

Posture and balance

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2
Q

Where is the vestibular system located

A

In the inner ear, embedded in the temporal bone

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3
Q

What is the vestibular system composed of

A

series of fluid filled membraneous tubes = labyrinths

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4
Q

What is the apparatus of the vestibular system

A

3 semi circular canals
Utricle
Saccule

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5
Q

What is the position of the semi circular canals

A

Are three dimensional due to being all right angled to each other

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6
Q

What is the swelling at the base of each semicircular canal called

A

Ampulla

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7
Q

Where is the utricle located

A

Swelling at the base of all the semicircular canals connecting them all

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8
Q

Where is the saccule located

A

The swelling underneath the base of the utricle

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9
Q

Where is sensory hair cells located in the vestibular apparatus

A

The ampulla of semicircular canals
Saccule
Utricle

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10
Q

What is the collective name of the utricle and the saccule

A

Otolith organs

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11
Q

What is the overall function of the otolith organs utricle

A

Detects linear acceleration and encode the position of the head in space

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12
Q

What is the overall function of the otolith organs saccule

A

detects vertical movement

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13
Q

What is the overall function of the semicircular canals

A

Detects rotational acceleration

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14
Q

Where are the sensory cells of the semicircular canals embedded

A

The ampulla

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15
Q

What is the sensory receptors called inside the ampulla

A

Cristae

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16
Q

What does the cristae consist of

A

A cupula - a flexible gelatinous strucutre

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17
Q

How is the crisate arranged in the ampulla

A

Stretches over the width of the ampulla

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18
Q

What is further embed in the cupula of the ampulla

A

Cilia of hair cells, which act as receptor cells

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19
Q

What is the purpose of the cilia of hair cells in the cristae

A

Synapse directly with the sensory neurones of the vestibular nerve

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20
Q

How is the cilla of hair cells receptors activated

A

By the movement of the endolmlyph in the semicircular canal pushing the gelatinous cupola of the cristae

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21
Q

What moves first when rotation of the skull occurs

A

The ampulla

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22
Q

Why doesn’t the endolymph move at first on rotation

A

As isn’t embedded in the skull

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23
Q

How does the hair cells in the Cupula detect rotational acceleration

A

Due to the inertia of the endolymph producing a drag which bends the cupula in the opposite direction of rotational movement and overall activates the cilla

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24
Q

What cause the endolymph to catch up the the rotational speed

A

Rotating at a constant velocity for several seconds

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25
Q

What is the affect of the endolymph catching up with the rotational speed

A

Endolymph now rotating at the same velocity so remove the sheering force, and cuppa no longer distorted

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26
Q

How does dizziness occur if you suddenly stop high velocity rotation

A

endolymph to continue to move due to momentum creating a continuing sense of movement

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27
Q

What is the two types of cilia hair cells

A

Kinocillium - single very large

Stereocillia - smaller series

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28
Q

What does distortion of the cilla in the direction of the Kinocillium cause

A

Depolarisation and increase discharge of the APs in the vestibular nerve

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29
Q

What does distortion of the cilia away from the Kinocillium lead to

A

Hyperpolorisation and decrease discharge of APs in the vestibular nerve

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30
Q

What does movement of the kinocillium allows the brain to determine

A

Movement in time and space

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31
Q

Why is the orientation of the cupula all slightly different

A

So the brain can build a 3D image of body position using the pattern of firing and inhibition received.

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32
Q

Where does the integration of the sensory information from vestibular apparatus take place

A

The cerebellum

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33
Q

When you stop rotating after rotating at constant velocity, what happens to the movement of endolymph and the cupola

A

The endolymph continue to move die to momentum

But the sheering of the cupula is in the opposite direction that at the start

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34
Q

What is the name of the sensory receptors in the otolith organs

A

Maculae

35
Q

How is the Maculae orientated in the utricle

A

In the horizontal plane

36
Q

How is the Maculae orientated in the saccule

A

In the vertical plane

37
Q

What is the structure of the maculae

A

Set of cilla which embed into the gelatinous mass called the otolith membrane

38
Q

What is embedded into the otolith membrane

A

CaCO3 crystals called otoliths.

39
Q

What affect the positioning of otolith crystals

A

Gravitational forces

40
Q

What doesn’t have much input on the positioning of the otolith crystals, why?

A

Endolymph

as otoliths have greater density

41
Q

How do the macule in the utricle detect the tilting of you head

A

Tilting the head moves the otoliths and the otolith membrane in which they are embedded.

This distorts the jelly, and moves the cilia

42
Q

What head tilt moves the otoliths in the direction of the kinocillium resulting in depolarisation

A

Backward tilt

43
Q

What occurs when the head it tilted forward

A

Otoliths move in the opposing direction of the kinocillium resulting in hyperpolorisation decreasing AP discharge

44
Q

What do the vertically orientated macule in the saccule respond to

A

Vertical forces e.g. movement in a lift

45
Q

What provides information of the orientation of the head when lying down

A

The macula in the saccule

46
Q

Where does the information to the brain via the vestibular nerve all originate from

A

The three cristae of the semicircular canals

and the two macule of the otolith organs

47
Q

Where does many sensory afferents of the vestibule nerve terminate

A

In the vestibular centres in the medulla

48
Q

How does the cerebellar centres associate with the vestibular centres

A

By co-ordinating the postural muscles required to maintain balance

49
Q

Where does vestibular nuclei receive input from

A

Proprioceptors signalling limb and body position,
Neck,
Eye muscles

50
Q

What is the vestibular nuclei

A

cranial nuclei for the vestibular nerve

51
Q

Where is the vestibular nuclei found

A

grouped in both the pons and the medulla in the brainstem

52
Q

How and where do the projections from the vestibular nuclei project

A

Project ipsilaterally, bilaterally and contra-laterally to descending motor pathways and the extra ocular nuclei/muscles

53
Q

How does vestibular nuclei project to the cerebral cortex

A

Via the thalamus

54
Q

What does the vestibular nuclei project to the cerebral cortex

A

perception of movement and body position = kinaesthesia.

55
Q

Name three vestibular system reflexes

A

Tonic labyrinthine reflex

Dynamic righting reflex

Vestibulo-occular relflex

56
Q

What does the vestibule system reflexs involve

A

Vestibulocortical and vestibulospinal tracts

57
Q

What occurs in the tonic labyrinthine reflex

and how does it happen?

A

The axis of the head is kept in a constant relationship with the rest of the body.

Use information from maculae and neck proprioceptors

58
Q

What occurs in the dynamic
righting reflex

and how does it happen?

A

Rapid postural adjustments that are made to stop you falling when you trip.

Long reflexes, involving extension of all limbs

59
Q

How does vestibular apparatus have a strong connection to visual apparatus

A

Afferents from the semi-circular canals project and connect (within the vestibular nuclei) to afferent fibres travelling to the extraocular nuclei and thus have strong input to influencing eye movement.

60
Q

What demonstrates the strong association between visual system and postural control

A

An increased difficulty experienced with balance when you close your eyes

61
Q

How do people with vestibular apparatus destruction maintain good balance and how do they loose balance

A

Balance is good if movement is relatively slow and eyes are open

Balance is lost if they close their eyes

62
Q

What is the two vestibulo-ocular reflex

A

Static reflex

Dyanmic vestibular nystagmus

63
Q

What occurs in the static reflex

A

When you tilt your head, the eyes intort/extort to compensate, so that over a certain range, the image stays the right way up

64
Q

What occurs in the dynamic vestibular nystagmus

A

series of saccadic eye movements that rotate the eye against the direction of rotation of the head and body so that the original direction of gaze is preserved despite head rotating

65
Q

What occurs when the eyeball comes to the end of its range of movement

A

The extent of eye movement is restricted so it rapidly flicks back (nystagmus) to looking straight ahead

66
Q

Define nystagmus

A

Rapid involuntary movement of the eye

67
Q

If the head is rotating right what is the direction of the nystagmus

A

Right

68
Q

In Post rotary nystagmus (at the end of rotation and nystagmus has occurred in the direction of the rotation)

Why then do you then get nystagmus in the opposing direction

A

As In the deceleration the endolymph is catching up and now pushing the cupula in the opposite direction

69
Q

How in caloric stimulation when the ear is washed with either cold or warm fluid is the vestibular system stimulated

A

As fluid gets through the thin bones and sets up convection current affecting the endolymph

70
Q

What is the affect of warm fluid >37C

A

Sets up nystagmus towards the affected side

71
Q

What is the affect of cold fluid <37C

A

sets up nystagmus away from the affected side

72
Q

What are the two tests that check vestibular function by investigating nystagmus s

A

Caloric stimualtion
(ear washed with water)

Post rotary nystagmus (rotated in a chair)

73
Q

What is the symptoms experienced due to caloric stimulation

A

Nausea

Vomiting

74
Q

Why is it good to test fro nystagmus

A

As shows if any lesions are present in the periphery to central vestibular pathways

75
Q

Powerful maintained stimulation of the vestibular system can cause what

A

Kinetosis - motor sickness

76
Q

Why does motion sickness/kinestosis occur in moving vehicles

A

Visual and vestibular system inputs to the cerebellum are in conflict

77
Q

How does the cerebellum generate the symptoms of motion sickness

A

sends“sickness signal” to the hypothalamus to bring about the autonomic changes

78
Q

What is the autonomic nervous symptoms caused by motion sickness

A 
Nausea 
Vomiting 
decreased blood pressure 
Dizziness 
Sweating 
Pallor

= all equal autonomic

79
Q

What symptoms does acute infection of vestibular apparatus - labyrinthitis

A

Autonomic Nervous system symptoms

Vertigo

80
Q

what is the symptoms of Mieinieres disease

A

Vertigo
Nausea
Nystamgus
Tinnuitis

81
Q

How does menieres disease affect vestibular function

A

as associated with overproduction of endolymph

82
Q

What drugs is the inner ear sensitive towards

A

Streptomycin

83
Q

How does a lesion of the brain stem affect vestibular function

A

Can cause nystagmus at rest

The Nervous System: Physiology (15 decks)

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