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Nervous System > Vestibular Function > Flashcards

Vestibular Function Flashcards

1
Q

The vestibular system is in control of

A

posture and balance

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2
Q

What is the vestibular system?

A

A sensory system

Series of fluid filled membranous labyrinths which are embedded in the temporal bone

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3
Q

Components of the vestibular system

A

3 semi-circular canals
Utricle
Saccule

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4
Q

Sensory hair cells are contained within what parts of the vestibular system

A

Utricle
Saccule
Ampulla

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5
Q

How do the otolith organs (utricle and saccule) work?

A

They detect linear acceleration and encode information about the position of the head in space

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6
Q

Back/front tilt of the head is detected by

A

the utricle

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7
Q

Vertical movement of the head is detected by

A

the saccule

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8
Q

The semi-circular canals detect

A

rotational acceleration

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9
Q

The cupula respond to

A

movement of the endolymph fluid within the canals

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10
Q

The cilia in the gelatinous cupula detect

A

rotational acceleration

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11
Q

What are the types of cilia in the gelatinous cupula?

A

Single large kinocilium

Progressively smaller stereocilia

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12
Q

Distortion of the cilia in the direction of the kinocilium causes

A

depolarisation and increased discharge off the action potentials in the vestibular nerve

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13
Q

Distortion of the cilia away from the kinocilium causes

A

hyperpolarisation and decreased discharge of action potentials in the vestibular nerve

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14
Q

Distortion of the kinocilium allows

A

the brain to determine movement in time and space

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15
Q

The sensory apparatus of the utricle and saccule are collectively known as

A

the maculae

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16
Q

The macula in the utricle are oriented on what plane?

A

Horizontal

17
Q

The macula in the saccule are orientated on what plan?

A

Vertical

18
Q

Tilt of the head is detected by

A

the macula in the utricle

19
Q

Do otoliths or endolymph have a greater density?

A

Otoliths - so are subject to a greater force of gravity

20
Q

What part of the brain co-ordinates the postural muscles required to maintain balance?

A

Cerebellar centres

21
Q

Projections from the vestibular nuclei on one side project

A

ipsilaterally, bilaterally and contralaterally to descending motor pathways

22
Q

Vestibular nuclei receive input from

A

proprioceptors signalling limb and body position, and from neck and eye muscles

23
Q

Vestibular nuclei project via

A

the thalamus to the cerebral cortex to give perception of movement and body position

24
Q

What is kinaesthesia?

A

Conscious awareness of where the body is and its movements

25
Q

What tracts are involved in the vestibular system reflexes?

A

Vestibulocortical

Vestibulospinal

26
Q

Function of tonic labyrinthine reflexes

A

keep the axis of the head in a constant relationship with the rest of the body using information from maculae and neck proprioceptors

27
Q

How do dynamic righting reflexes work?

A

Rapid postural adjustments made to stop you falling when you trip
Long reflexes involving extension of all limbs

28
Q

How do vestibulo-ocular reflexes work?

A

Afferents from semicircular canals project and connect to extra ocular nuclei and have strong input to influencing eye movement
Visual system sends powerful descending projections which control posture

29
Q

How does static reflex work?

A

When the head is tilted, eyes intort/extort to compensate so that (over a certain range) the image stays the right way up

30
Q

How does dynamic vestibular nystagmus work?

A

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

31
Q

What is vestibular nystagmus?

A

Rapid, involuntary eye movements related to a damaged vestibular system

32
Q

What can be done to test the horizontal semicircular canal?

A

Caloric stimulation - outer ear washed with cold or warm fluid

33
Q

Warm fluid causes nystagmus towards

A

the affected side

34
Q

Powerful maintained stimulation of the vestibular system can give rise to

A

kinetosis (motion sickness)

35
Q

Kinetosis iis most likely to occur if

A

visual and vestibular inputs to the cerebellum are in conflict

Nervous System (44 decks)

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