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Neuroanatomy Exam II > The Vestibular pathways > Flashcards

The Vestibular pathways Flashcards

1
Q

What types of information is vestibular data integrated with by the CNS?

A

Visual and proprioceptive data to maintain postural balance and permit visual fixation during movements of the head.

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2
Q

What do central vestibular pathways provide important connections to in order to facilitate postural balance and visual fixation during movements of the head?

A

Motor neurons in the spinal cord and brainstem that permits reflex control of muscles that determine balance and eye position.

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3
Q

Do vestibular pathways connect to the cerebellum or cerebrum?

A

Yes, connects to both

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4
Q

What type of neurons are primary sensory neurons of the vestibular system?

A

Bipolar neurons

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5
Q

What ganglion is responsible for primary sensory neurons?

A

Cell bodies that comprise the vestibular ganglion or Scarpa’s ganglion

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6
Q

What do the peripheral processes from the vestibular ganglion innervate?

A

Hair cells of the macula and crista ampullaris

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7
Q

What do central processes from the vestibular ganglion do?

A

enter the brainstem as part of the VIII nerve

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8
Q

How do central axons of the vestibular primary sensory neurons enter the cerebellum?

A

THrough the inferior cerebellar peduncle

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9
Q

Where do the central axons of the vestibular primary sensory neurons project to in the cerbellum (ie: which cerebellar area)

A

Archicerebellum including the flocculus, nodulus, and fastigial nucles

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10
Q

Where do most central axons terminate for the vestibular primary sensory neurons?

A

in the vestibular nuclear complex

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11
Q

What is included in the vestibular nuclear complex?

A

Complex includes 4 nuclei located in the floor of the IV ventricle in the pons and medulla

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12
Q

What do projections to the spinal cord from the vestibular nuclear complex do?

A

Influence motor neurons

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13
Q

Is the vestibulospinal tract ipsilateral or contralateral?

A

ipsilateral

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14
Q

Where does the vestibulospinal tract extend in the spinal cord?

A

Extends the entire length of the cord

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15
Q

Where does the vestibulospinal tract terminate?

A

On interneurons or motor neurons which influence motor neurons that innervate postural muscles

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16
Q

What is the function of the vestibulospinal tract ?

A

Tract helps to regulate the tone of postural muscles (of the trunk and proximal extremities) so that when the the head is moved, body equilibrium is maintained

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17
Q

Is the Medial Longitudinal fasciculus tract ipsilateral or contralateral?

A

Includes ipsilateral and contraclateral axons from the vestibular nuclear complex

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18
Q

Where do Medial Longitudinal fasciculus tract axons terminate?

A

Monstly in the cervical cord segments on interneurons or motor neurons

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19
Q

What is the function of the Medial Longitudinal fasciculus tract ?

A

Helps to regulate tone of the neck muscles in order to maintain the balance of the head as it moves through space

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20
Q

What do projections of the vestibular nuclear complex to the brainstem areas do?

A

Provide conjugate or parallel movemnts of the eyes that will be coordinated with movements of the head and permits visual fixation (ie: on a stationary object as head moves

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21
Q

Are projections of the vestibular nuclear complex to the brainstem areas ipsilateral or contralateral?

A

Projections are both ipsilateral and contralateral that make up the ascending medial longitudinal fasciculus

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22
Q

What do the fibers of the ascending medial longitudinal fasciculus influence?

A

DIrectly or indirectly influence the activity of cranial nerves III, IV, VI

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23
Q

What do the influence on CN III, IV, VI by the ascending longitudinal fasciculus do?

A

These connections provide that both eyes will move together in parallel and in an opposite direction of the head as the head moves

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24
Q

Where do primary neurons and second order neurons that project data to the cerebellum project to?

A

SOme primary neurons and some second order neurons of the VIII nerve project directly to the archicerebellum

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25
Q

How do fibers from the vestibular information reach the archicerebellum?

A

They project through the inferior cerebellar peduncle

26
Q

What does the archicerebellum do with the vestibular information received?

A

Uses the information to influence the activity of muscles used in posture, balance and eye positioning

27
Q

Where do neurons of the archicerebellum carrying vestibular information project to?

A

Influence motor control by projecting axons to the vestibular nuclear complex and thus influencing the activity of vestibulospinal tract and medial longitudinal fasciulus which, in turn, influence motor neurons

28
Q

What areas of the telencephalon are vestibular pathways found?

A

AReas of the parietal, temporal and insula lobes that receive vestibular data

29
Q

What is the significance of vestibular pathways being found in the parietal, temporal and insula?

A

Contribute to one’s conscious awareness of the precise potion of the head in space

30
Q

As the body and head are rotated to the right, what happens to endolymph flow in the right lateral duct?

A

Endolymph flow is ampullopedal (increased discharge from the crista ampullaris)

31
Q

As the body and head are rotated to the right, what happens to endolymph flow in the left lateral duct?

A

Endolymph flow is ampullofugal (decrease discharge from the crista ampullaris)

32
Q

Track the relay of vestibular data

A

Vestibular data -> vestibular nuclear complex -> vestibular nuclear complex -> modiefies activity of central vestibular pathways (V-S tract, MLF) -> influence motor neurons that innervate muscles used in control of posture and eye position

33
Q

As the body moves to the right, what happens to the postural and axial muscles?

A

The muscles change tone to maintain balance (contract on left) to keep one from fallin in the direction of the rotation

34
Q

What is a vestibulo-ocular or vestibulokinetic reflex?

A

Enables the eyes to maintain visual fixation on stationary objects as the head is moving

35
Q

How the eyes move initially while the head rotates to the right?

A

Initially eyes will slowly drift to the left known as the slow drift phase of vestulo-ocular reflex

36
Q

What cranial nerves are required to allow for the slow drift phase of the vestibulo-ocular reflex that causes the eyes to drift to the side opposite of rotation?

A

CN III and VI

37
Q

What does CN III do in the case of right head rotation?

A

Innervates the right medial rectus muscle

38
Q

What does CN IV do in the case of right rotation of the head?

A

Innervates the left lateral rectus muscle

39
Q

What is the slow drift phase of the reflex dependent on?

A

Dependent on the vestibular data from the inner ear and is mediated by the MLF (therefore is vestibular driven)

40
Q

What happens after slow drift of the eyes to the left occurs (with right rotation of head) and what is it known as?

A

The eyes quickly move to the right, known as the fast drift phase of the vestibulo-ocular reflex

41
Q

What does the fast drift phase of the vestibulo-ocular reflex require?

A

Requires facilitation of the right VI nerve that innervates the right lateral rectus and the left III nerve that innervates the left medial rectus

42
Q

Is the fast drift phase a vestibular driven?

A

No, it is considered a corrective maneuver and controlled by a different area of the brain

43
Q

What is nystagmus?

A

Patterns of slow and fast drift movements of the eyes

44
Q

What direction of movement designates the direction of nystagmus?

A

The direction of the fast component designates the direction of nystagmus

45
Q

So with rotation of the head to the right which side is the nystagmus to?

A

right side

46
Q

What are the different tests for the integrity of the vestibular system?

A

Rotation test

Caloric test

47
Q

What occurs in the rotation test?

A

Patient is placed in a swivel test
Head tilted to about 30 degrees
Rotate the patient about 10-15 times to the right at a constant velocity
STop the chair and have the patient stand and attempt to focus and point at a distant object

48
Q

Why is a patient’s head tilted to about 30 degrees in the rotation test?

A

places the semicircular ducts in horizontal plane

49
Q

Why is the patient rotated 10-15 times at a constant velocity?

A

It allows the endolymph to move at the same speed as the head and lateral semicircular ducts therefore the vestibular receptor reaches a static discharge

50
Q

During the post-rotation phase of the rotation test what happens to the endolymph in the lateral ducts?

A

The fluid continues to move and rotate to the right

51
Q

During the post-rotation phase of the rotation test what happens to the endolymph in the left lateral duct?

A

Moves ampullopedal (increase discharge of cristae)

52
Q

During the post-rotation phase of the rotation test what happens to the endolymph in the right lateral duct?

A

Moves ampullofugal (decrease discharge of cristae)

53
Q

During the post-rotation phase of the rotation test what direction does the vestibular data supplied to the CNS suggest?

A

The head is rotating to the left

54
Q

What movement ampullofugal or ampullopedal is relayed to the CNS as the direction of movement?

A

Ampullopedal (ie: if ampullopedal movement was on the right then the CNS interprets the had as moving to the right)

55
Q

What direction will the eyes display nystagmus during the post-rotation phase of the rotation test

A

Slow drift to the right
fast drift to the left
Therefore, left nystagmus

56
Q

Towards which side will the patient fall During the post-rotation phase of the rotation test?

A

They will fall to the right (opposite side of perceived rotation) as the CNS “thinks” the head/body is rotating to the left

57
Q

Which side do the muscles contract During the post-rotation phase of the rotation test?

A

The right side therefore causing the patient to fall towards the right

58
Q

When attempting to point at a distant object During the post-rotation phase of the rotation test, where will they point?

A

The patient will past point to the right (side opposite of perceived rotation

59
Q

How does one perform the caloric test?

A

1) tilting the patient’s head backs about 60 degress

2) irrigate the external auditory meatus of one ear with either warm or cool water

60
Q

In the caloric test why is the patient’s head backwards about 60 degrees?

A

Places the lateral ducts n a vertical position

61
Q

What is the normal responsive response of a caloric test?

A

COWS
Cold water -> fast drift to the opposite side of irrigation
Warm water -> fast drift to the same side of irrigation

62
Q

What is the presumed mechanism of the caloric test?

A

Cool water (right ear) -> ampullo-fugal movements -> decrease discharge of crista ampullae -> brain thinks it is in left rotation -> slow drift to right, fast drift to left, fall to right, over point to right

Neuroanatomy Exam II (11 decks)

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