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Neurology > Lecture 6 Vestibular Function > Flashcards

Lecture 6 Vestibular Function Flashcards

1
Q

What is the vestibular system

A

A sensory system essential in the control of posture and balance. Found in the inner ear, it is a series of fluid-filled membranous tubes, (labyrinths), which are embedded in the temporal bone filled with endolymph that move hair cells within them.

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2
Q

What does the vestibular apparatus consist of

A

3 semi-circular canals
Utricle
Saccule

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3
Q

What are the swellings at the bottom of the semi-circular canals called

A

Ampulla

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4
Q

What do the ampulla contain

A

Sensory hair cells (embedded in cupula)

Cristae (inside is cupula)

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5
Q

What do the utricle and the saccule contain

A

Sensory hair cells

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6
Q

What are the utricle and the saccule collectively known as

A

Otolith organs

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7
Q

What type of the movement does the utricle respond to

A

Back/front tilt

Horizontal acceleration

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8
Q

What type of movement does the saccule respond to

A

Vertical acceleration

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9
Q

What type of movement does the semi-circular canals respond to

A

Rotational acceleration

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10
Q

The hair cells in side the cupola of the Cristae in the ampulla directly synapse with what nerve

A

Sensory neuron of the vestibular nerve (CNVIII)

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11
Q

How is the receptor cells in the ampulla activated

A

Movement of endolymph push the cupula

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12
Q

What are the types of hair cells are in the ampulla

A

Single very large kinocilium

Progressively smaller stereocilia

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13
Q

Distortion of the cilia in the direction of the kinocilium causes what

A

Depolarisation and increased discharge of APs in the vestibular nerve

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14
Q

Distortion of the cilia away from the kinocilium leads to what

A

Hyperpolarisation and decreased discharge of APs in the vestibular nerve

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15
Q

What is the sensory apparatus of the utricle and saccule called

A

Maculae

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16
Q

What is the orientation of the maculae in the utricle

A

Horizontal

17
Q

What is the orientation of the maculae in the saccule

A

Verticle

18
Q

Describe the structure of the maculae

A

Have set of cilia (one kinocilium and a series of stereocilium) which protrude into a gelatinous mass called the otolith membrane

19
Q

What is embedded in the otolith membrane

A

CaCO3 crystals called otoliths

20
Q

What do the Otoliths do

A

Move in reposes to gravitational forces

21
Q

What does titling the head do to the otoliths

A

Tilting the head moves the otoliths and the otolith membrane in which they are embedded. This distorts the jelly and moves the cilia

22
Q

Name the 3 Vestibular System Reflexes

A

Tonic labyrinthine reflexes
Dynamic righting reflex
Vetsibulo-ocular reflexes

23
Q

Define Tonic labyrinthine reflexes

A

Keep the axis of the head in a constant relationship with the rest of the body. Use information from maculae and neck proprioceptors

24
Q

Define Dynamic righting reflex

A

rapid postural adjustments that are made to stop you falling when you trip. Long reflexes, involving extension of all limbs. Most profound in cats.

25
Q

Define Vestibulo-ocular reflexes

A

strong association is evident between the vestibular apparatus, the visual apparatus and postural control.

26
Q

What is 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.

27
Q

What is dynamic vestibular Nystagmus

A

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.

28
Q

How can you test for vestibular function

A

Post-rotary nystagmus

Caloric stimulation

29
Q

Explain the results of the caloric stimulation

A

Cold opposite side

Warm same side

30
Q

Where else can nystagmus be seen except for abnormal vestibular dysfunction

A

Lesion to peripheral or central vestibular pathways

31
Q

Powerful maintained stimulation of the vestibular system can give rise to what

A

Kinetosis (motion sickness)

32
Q

When is motion sickness most likely to occur

A

if visual and vestibular system inputs to the cerebellum are in conflict e.g. if the vestibular system indicates rotation but the visual system does not

33
Q

What is Labyrinthitis

A

Acute interference with normal vestibular function as a result of infection

34
Q

What is Meniere’s disease

A

Associated with over production of endolymph causing  pressure

Neurology (44 decks)

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