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neuroscience > Vestibular system > Flashcards

Vestibular system Flashcards

1
Q

Where does the vestibular system lie?

A

Deep within the temporal bone adjacent to the cochlea

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2
Q

What is the vestibule, where does it lie, what does it communicate with?

A

Central part of the bony labyrinth.

Communicates anteriorly with the cochlea and posteriorly with the semi-circular canals.

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3
Q

How is the vestibule separated from the middle ear?

A

Oval window

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4
Q

What are the three semi-circular canals?

A

Anterior, lateral and posterior

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5
Q

What lies inside the vestibule?

A

Saccule and utricle

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6
Q

Where does endolymph from the saccule and utricle drain?

A

Into the endolymphatic duct

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7
Q

Endolymph composition

A

High K+ content (like ICF)

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8
Q

Where do cell bodies of vestibular nerves lie?

A

Vestibular ganglia

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9
Q

Where do vestibular nerves project to?

A

Vestibular nuclei (medial, lateral, superior and inferior) and cerebellum

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10
Q

What are ampullae?

A

Swellings at the base of the semi-circular canal where sensory receptors lie

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11
Q

Where do ampullae stereocilia project?

A

Into gelatinous cupula

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12
Q

What movements do semi-circular canals respond to?

A

Rotation and angular acceleration

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13
Q

What happens in the ampullae upon angular acceleration?

A

Endolymph lags behind the head due to the inertia of the fluid, this flexes the cupula and bends the cilia

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14
Q

What happens when hair cells bend towards the kinocilium?

A

Hair cell depolarises and leads to increased glutamate release onto CNVIII which generates a train of action potentials in the vestibular nerve

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15
Q

What happens when the hair cells bend away from the kinocilium?

A

Hair cells hyperpolarize leading to inhibition of transmitter release.

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16
Q

Does hair cells stimulation cause discharge?

A

No, only increase/decrease discharge rate compared to tonic resting position.

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17
Q

What happens inside the semi-circular canals in rotation?

A

Displacement of the fluid in the horizontal canal -activating the vestibular system on one side (rapid firing increase), whilst inhibiting it on the other side.

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18
Q

How long does the vestibular response to head rotation in one direction last and why?

A

Happens immediately but ceases after several seconds (about 6 secs) (falling to zero) even when the head is still rotating - this is because the fluid starts to rotate as well, hair bundle is no longer deflected.

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19
Q

What happens inside the semi-circular canals when the head stops rotating?

A

Endolymph continues to move around, we perceive this as the opposite, causing an imbibition of the stereocilia

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20
Q

What are the axes that the semi-circular canals detect?

A

Pitch (y-axis nodding yes), roll (x-axis shoulder to shoulder), yaw (z-axis shaking no)

21
Q

Each semicircular canal (anterior, posterior or horizontal) responds maximally to

A

A rotation about an axis perpendicular to its plane.

22
Q

Fibres from the horizontal and anterior canals primarily synapse in the

A

Superior, lateral and medial nuclei

23
Q

Fibres from the posterior canals primarily synapse in the

A

Superior, descending (inferior) and medial nuclei

24
Q

In the saccule and utricle what do the hair cells project into?

A

Gelatinous otolithic membrane and is overlaid by otoconia/otoliths

25
Q

What is the otolithic membrane covered by (saccule and utricle)?

A

Otoconia/otoliths

26
Q

What are otoconia/otoliths?

A

Calcium carbonate crystals that have inertia.

27
Q

What are type I hair cells?

A

Surrounded by an afferent calyx

28
Q

What are type II hair cells

A

More efferents that synapse directly on the hair cell body (punctate boutons)

29
Q

How is the saccule/utricle membrane divided?

A

Central striola, on either side there is a division of hair cell type

30
Q

What does the saccule detect?

A

Vertical linear acceleration

31
Q

What does the utricle detect?

A

Horizontal linear acceleration

32
Q

Why are hair cells arranged in the way they are in the saccule and utricle?

A

So they can detect changes in motion in any direction

33
Q

What responds to gravity?

A

Saccule and utricle

34
Q

Afferents from the utricle and saccule terminate mainly in the

A

Inferior and medial nucleus. Lateral nuclei receive synapses from saccule and utricle too.

35
Q

Vertigo

A

Inputs from vestibular system do not match environment

36
Q

How does the cerebellum influence the VOR?

A

Visual feedback that can detect errors in the VOR is too slow to correct the very rapid responses generated by the VOR during a head movement.

These adaptive changes are lost following a lesion of the cerebellar flocculus.

37
Q

The vestibular part of the cerebellum is the

A

Flocculus and nodulus

38
Q

Benign paroxysmal positional vertigo (BPPV)

A

Pieces of otolithic membrane break off and fall into semi-circular canal displacing fluid. Common in elderly.

39
Q

Meniere’s disease

A

Improper drainage of endolymph via endolymphatic duct.

Gentamycin can be used to kill hair cells in severe cases.

40
Q

Vestibular nystagmus

A

VOR rapid eye movement and slow movement to reset eye gaze

Vestibular nystagmus is normal when a person is being rotated.

41
Q

Egocentric coordinate system.

A

Relative position of parts of body with respect to each other

42
Q

Exocentric coordinate system.

A

Relative position of body with respect to environment

43
Q

Geocentric coordinate system.

A

Orientation of body in gravitational field

44
Q

Vestibulocollic reflex

A

Neural reflex that activates neck muscles when head motion is sensed by the vestibular organs in the inner ear

Mediated by the medial vestibulospinal tract

45
Q

The semi-circular canals lie within the…

A

Petrous part of the temporal bone

46
Q

The semi-circular canals are concerned with…

A

Angular acceleration

47
Q

The nerves innervating the utricle and saccule arise in the…

A

Vestibular ganglion

48
Q

The vestibular nuclei have strong interconnections with the…

A

Oculomotor nuclei

49
Q

The major target of the output from the vestibular part of the cerebellar cortex is the..

A

Fastigeal nucleus

neuroscience (19 decks)

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