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Control & Movement > Control L21 Vestibular System and Control of Posture > Flashcards

Control L21 Vestibular System and Control of Posture Flashcards

1
Q

What is the role of posture?

A

Maintain steady stance aka balance in the presence of gravity
Generate responses that anticipate goal-directed movements and uses reflexes and automatic response to cope with unexpected disturbances.

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2
Q

What modalities are involved in maintaining balance and posture?

A

Somatosensory muscle and joint proprioceptors
Vestibular system
Visual system

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3
Q

What section if the vestibular labyrinth is sensitive to head rotation?

A

Semicircular canals

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4
Q

What part of the vestibular labyrinth is involved in detecting force of gravity and tilt of the head?

A

Otolith organs which include the utricle and saccule

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5
Q

What ganglion is associated with the vestibular nerve?

A

Scarpa’s ganglion

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6
Q

What are the three semicircular canals?

A

Anterior
Posterior
Lateral

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7
Q

What links the three semicircular canals?

A

Ampullae

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8
Q

What is the vestibular apparatus separated into?

A
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9
Q

How do the soft membranous labyrinth and the surrounding bony labyrinth differ?

A
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10
Q

What makes up the vestibule?

A

Utricle and saccule aka the otolith organs

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11
Q

What nerves make of the vestibular branch of the vestibulocochlear nerve?

A
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12
Q

What are the 6 degrees of freedom of head movement?

A
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13
Q

What are the 3 translational degrees of freedom of head movement?

A
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14
Q

What are the 3 rotational degrees of freedom of head movement?

A
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15
Q

What motion is mainly detected by the otolith organs?

A
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16
Q

What movement is mainly detected by the semicircular canals?

A
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17
Q

What are the main structural features of the otolith organs?

A
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18
Q

What sensory detectors are found in the otolith organs?

A

Maculae

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19
Q

What are features of the hair cells in the vestibular system?

A

Made up of a hair bundle formed of one kinocillium and many (stereo)cilia
All cilia connected by top links
Bending of kinocilia and cilia produces firing in sensory nerve which is increased or decreased depending on direction of tilt - right = decreased firing/hyperpolarisation and left = increased firing/depolarisation.

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20
Q

What is released by hair cells to increase firing in the vestibular system?

A

Glutamate

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21
Q

What information is provided by the macula when activated by head displacement?

A

Static equilibrium (position relative to horizon)
Dynamic equilibrium (linear acceleration/deceleration)

22
Q

How are the macula organised in the utricle vs the saccule?

A

Utricle = horizontal organisation
Saccule = vertical organisation

23
Q

What is the striola?

A

The axis of mirror symmetry in the otolith organs such that hair cells on opposite sides have opposite polarisation. This means that tilt along the axis will excite hairs on one side and inhibit them on the other.

24
Q

What are the functional features of the semicircular canals?

A
25
Q

What is the structure of the crista ampularis?

A
26
Q

What are the functional features of the cupula?

A
27
Q

How are semicircular canals arranged?

A
28
Q

What is the push and pull mechanism of semicircular canals?

A
29
Q

Where does the medial vestibular nucleus send impulses?

A
30
Q

Where does the lateral vestibular nucleus send signals to?

A
31
Q

What is the path of the central vestibular pathways?

A
32
Q

What is the vestibulo-ocular reflex?

A
33
Q

What provides anticipatory and feedforwrad postural control?

A

Descending motor pathways

34
Q

What is the feedforward and feedback loop of postural control?

A

Central command leads to limb movement and feedforward/anticipation of postural adjustment.

Limb movement leads to postural instability which feedbacks to postural adjustment too.

35
Q

What are some postural reflexes?

A
36
Q

What are some diseases affecting the vestibular system?

A

Meniere’s syndrome
Bengin paroxysmal postitional vertigo
Vestibular neuritis, brainstem carcinoma, infarction and haemorrhage

37
Q

What is meniere’s syndrome?

A
38
Q

What is benign paroxysmal positional vertigo?

A
39
Q

What is a vestibular schwannoma?

A

Overproduction of Schwann cells info vestibulocochlear nerve leading to tinnitus, hearing loss, balance issues, facial weakness or numbness (as may press on facial or trigeminal nerves) and headaches.

40
Q

What is a medulloblastoma?

A
41
Q

What can occur due to ototoxicity?

A
42
Q

What is an ampulla?

A
43
Q

What is a cupula?

A
44
Q

What is displayed by the endolymph as the head rotates?

A

Inertia (endolymph lags behind movement). Displaces cupula with it in the opposite direction to movement (I.e. movement of the head to the right causes delayed displacement of cupula and hair cells to the left and vice versa)

45
Q

How do hair cells increase/decrease firing in the vestibular system?

A
46
Q

How are hair cells activated?

A
47
Q

How does horizontal eye movement occur when the head is rotated? E.g. to the right

A
48
Q

What is nystagmus?

A

When the eyes travel as far to one side (e.g. the left) as possible and rapidly flick back to the other (e.g. the right)

49
Q

What can be used to detect nystagmus?

A

Electrooculography

50
Q

What is caloric testing?

A
51
Q

What will the results of caloric testing be if there is a lesion in the medial longitudinal fasciculus?

A

Lesion causes loss of contralateral control so will lead to bilateral eye movement only instead of unilateral.

52
Q

How does alcohol affect the vestibular system?

A

Capula has a good blood supply where as the endolymph doesn’t, therefore when alcohol has been consumed, the capula becomes bouyant (as alcohol is less dense than the water in the endolymph) so when you lay down, the capula is displaced upwards. Movement of the cupula in the endolymph is exaggerated alongside eye movement. Mismatch between vestibular and visual modalities makes you feel ill. Once alcohol has left the bloodstream, the endolymph is less dense than the capula reducing movement of the capula again.

Control & Movement (36 decks)

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