Vestibular Function Flashcards

1
Q

What does the vestibular system control?

A

Posture and balance

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2
Q

Where is the vestibular system found?

A

Inner ear

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3
Q

Where are labyrinths embedded?

A

In the temporal bone

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4
Q

How many semi-circular canals are there?

A

3

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5
Q

What are the semi-circular canals all connected to?

A

Saccule

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6
Q

At what angle are the semi-circular canals to each other?

A

Right angles

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7
Q

What is the swelling at the base of the semi-circular canals called?

A

Ampulla

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8
Q

What do the ampulla contain?

A

Sensory hair cells

Cristae

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9
Q

What is the utricle?

A

Swelling at the anterior base of the ampulla

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10
Q

What is the saccule?

A

Swelling below the utricle

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11
Q

What are the utricle and saccule collectively known as?

A

Otolith organs

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12
Q

What do otolith organs detect?

A

Linear acceleration and encode information about the position of the head in space

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13
Q

What is back/front tilt detected by?

A

Utricle

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14
Q

What is vertical movement detected by?

A

Saccule

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15
Q

Where is rotational movement detected?

A

Semi circular canals

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16
Q

Where are the sensory cells of semi-circular canals located?

A

Ampulla

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17
Q

What are the sensory receptors in the ampulla called?

A

Cristae

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18
Q

What is located at the base of the cupula?

A

Sensory hair cells

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19
Q

What are cupula?

A

Gelatinous structure that stretch across the entire width of the ampulla

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20
Q

What do the cilia or hair cells synapse directly with?

A

Sensory neurons of the vestibular nerve

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21
Q

What is CN VIII?

A

Vestibulocochlear nerve

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22
Q

What movement do the hair cells in the gelatinous material of the ampulla detect?

A

Rotational acceleration

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23
Q

Does endolymph move automatically with skull rotation?

A

No fluid takes a while to move

24
Q

Does endolymph more as quickly as the skull?

A

No

25
Q

Does the ampulla move instantly with head movement ?

A

Yes because it it embedded in the skull

26
Q

What happens to endolymph when the head moves?

A

Initially it does not move because of its intertia

Then produces a drag in the opposite direction which bends the cupula and the cilia embedded in it

27
Q

If you rotate constantly and the endolymph catches up what happens if you stop suddenly?

A

Endolymph continues to move and spin

Creating the a continous sense of movement and dizziness

28
Q

What is vertigo?

A

The perception of movement in the absence of movement

29
Q

What are the 2 types of cilia hair cells in the ampulla?

A

Kinocilium

Stereocilia

30
Q

What does distortion of the cili in the direction of the kinocilium cause?

A

Depolarisation and increased discharge of AP in vestibular nerve

31
Q

What does distortion of cilia away from the kinocilium cause?

A

Hyperpolarisation and decreased discharge of AP in the vestibular nerve

32
Q

Where does much of the cilia movement sensory information integrated?

A

In the cerebellum

33
Q

What is the sensory apparatus of the utricle and saccule collectively known as?

A

Maculae

34
Q

Which plane are the macula in the utricle orientated?

A

Horizontal plane

35
Q

Which plane are the macula in the saccule orientated?

A

Vertical plane

36
Q

What are the cilia in the maculae called?

A

Kinocilium

Stereocilium

37
Q

What is embedded in the otolith membrane?

A

crystals called otoiths

38
Q

Where is tilt of the head detected?

A

By the macula in the utricle

39
Q

What gives orientation of the head when lying down?

A

Macula in the saccule (vertical plane)

40
Q

What does backwards tilt of the head cause?

A

Moves the otolith crystals in the direction of the kinocilium causing depolarisation and increase in AP

41
Q

What does forwards tilt of the head cause?

A

Moves the otolith crystals away from the kinocilium cause hyperpolarisation and decrease in AP

42
Q

Why do the macula not have the same mechanisms with endolymph?

A

Because the bones in the skull do not move alot with linear or vertical movements

43
Q

What is kinaesthesia?

A

Being aware of where you body is in time and space

44
Q

Where do vestibular nuclei receive input from?

A

Proprioceptors signalling limb and body position

Also from neck and eye muscles

45
Q

Where do vestibular nuclei project via?

A

The thalamus to the cerebral cortex

To give perception of movement and body position

46
Q

What descending tracts are involved in vestibular system reflexes?

A

Vestibulocortical

Vestibulospinal tracts

47
Q

What is the tonic labryinthine reflex?

A

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

48
Q

What is the dynamic righting reflexes?

A

Rapid postural adjustments that are made to stop you falling when you trip
Involves extension of all of the limbs

49
Q

What is the vestibulor-ocular reflexes?

A

Strong associations is evident between the vestibular apparatus , the visual apparatus and postural control 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.

50
Q

What is the static reflex?

A

The intorsion and extorsion of the eyes to compenstae for tilt of the head

51
Q

What is kinetosis?

A

Motion sickness

52
Q

What can powerful maintained stimulation of the vestibular system cause?

A

Motion sickness

53
Q

What are the symptoms of motion sickness?

A
Nausea
Vomiting 
Decrease in BP 
Sweating 
Pallor 
Dizziness
54
Q

What causes motion sickness

A

If the visual and vestibular system inputs to the cerebellum are in conflict

55
Q

What can lesions of the brain stem lead to?

A

Nystagmus at rest