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704 > Cranial Nerves _ Oculomotor > Flashcards

Cranial Nerves _ Oculomotor Flashcards

1
Q

For the visual system to work efficiently, both eyes must focus and remain focused on:

A

an object so the information can reach cortex in a form that can result in vision.

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2
Q

While we can detect objects over a large range extending into the periphery, we “see” objects only when:

A

they are focused on the fovea.

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3
Q

The oculomotor system, controlling the movement of our eyes, is designed to (2 functions):

A

1) bring targets onto the fovea, and 2) keep them there.

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4
Q

Historically, five movement systems have been identified that put the fovea on a target (both eyes in a conjugate manner; foveation) and keep it there. They are as follows:

A
  1. movements that stabilize the eye when the head moves

2. movements that keep the fovea on a visual target

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5
Q

Movements that stabilize the eye when the head moves are classified as ___________________ and ____________________.

A

• vestibulo-ocular
and
• optokinetic

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6
Q

Movements that keep the fovea on a visual target are classified as ___________________, ___________________ and ____________________.

A
  • saccade
  • smooth pursuit
  • vergence
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7
Q

vestibulo-ocular =

A

vestibular input holds images stable on retina during head and body movement; gaze stabilization

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8
Q

optokinetic =

A

visual input holds images stable on retina during sustained or slow head rotation

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9
Q

saccade =

A

brings new objects of interest onto fovea

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10
Q

smooth pursuit =

A

holds image of a moving target on the fovea

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11
Q

vergence =

A

adjusts eyes for viewing different distances in depth

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12
Q

In an oculomotor system that is functioning normally, the two eyes are:

A

“locked” together.

This allows both eyes to be focused on an object.

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13
Q

If the system becomes “unlocked” and the eyes focus on different targets (retinal disparity), what occurs?

A

diplopia or double vision occurs.

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14
Q

While the first four systems allow for the conjugate movements of the eyes for foveation, the vergence system allows for:

A

convergence or divergence (disconjugate movements)

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15
Q

What is diplopia?

A

the subjective complaint of seeing 2 images instead of one and is often referred to as double-vision.

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16
Q

The Saccade System is used to quickly:

A

reposition the eyes (fovea) to focus on an image that has suddenly been moved from the fovea.

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17
Q

Saccades can be ________________ or _________________.

A

horizontal or vertical

with the horizontal being the best understood from a neuronal pathway point of view.

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18
Q

What is the rapid eye movement required to bring the image back into focus?

A

saccade

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19
Q

Reading this card is done by a series of ________________ saccadic eye movements.

A

conjugate

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20
Q

Saccadic eye movements can be elicited by what types of inputs?

A

Visual input, auditory stimuli, memories of locations, or verbal commands.

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21
Q

Both eyes move in conjugate manner, in terms of ______________, _______________ and _____________ for reestablishment of the image on the fovea

A

velocity, amplitude and direction for reestablishment of the image on the fovea

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22
Q

This movement (reestablishment of image on fovea) is similar to the quick or saccade phase of _________________________.

A

vestibular nystagmus

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23
Q

This conjugate system is directed through a horizontal gaze center located in the ________________________________________,

A

pontine reticular formation (paramedian pontine reticular formation; PPRF)

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24
Q

Where is the PPRF located?

A

adjacent to the abducens nucleus.

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25
Q

The “upper motor neuron control” is a complicated system of interneurons, that involves a part of the middle frontal gyrus termed the _________________________ and the Superior Colliculus.

A

Frontal Eye Fields (FEF; area 8)

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26
Q

This cortical region is represented on both _____________________ and contains specific regions termed _______________ center, _______________center and a _______________ center.

A

hemispheres

horizontal gaze center, vertical gaze center and a vergence center

** These are separate and distinct regions within area 8.

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27
Q

Do vestibulo-ocular and Optokinetic reflexes work together?

A

Yes

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28
Q

As your head turns, your eyes are fixed on an object. Your eyes remain fixed and focused on that position by moving at the same speed as your head, but in the opposite direction. This is driven by the:

A

bilateral input of the vestibular system. [See diagram 15-8 in your text]

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29
Q

When the eyes reach a point in the periphery where they can no longer focus on that object, due to the image now being _________________________________ they reset to a new __________________________.

A

directed to the peripheral retina,

fixation point

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30
Q

This rapid movement is a saccade and is rapid enough that visual input is _______________________________.
The result is termed a ROTATORY NYSTAGMUS.

A

momentarily impaired until the foveas fixate on the next point.

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31
Q

This (rotatory nystagmus) has two components:

A
  1. the slow movement of fixation and

2. the rapid movement of resetting.

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32
Q

This vestibulo-ocular reflex is ______________ driven, due to the directional flow of endolymph _______________ the direction your head is turning.

A

vestibular

opposite

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33
Q

If the head continues to rotate, as on a spinning chair, the ________________ eventually “catches up” or stabilizes.
Then, the same pattern of following and ________________________ continues to take place as long as your head continues to turn.

A

endolymph

saccadic reset reaction

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34
Q

This continuation of following and resetting of the focal point is now driven by the _____________________ (the vestibular input is balanced).

A

optokinetic system

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35
Q

The optokinetic system requires input from the _________________ and _________________.

A

visual cortex and the superior colliculus.

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36
Q

Once the rotation is stopped, the eyes will react in the _______________ direction.

A

opposite

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37
Q

The slow following eye movement will be in the direction of ______________ and the saccade in the ________________ direction of prior rotation.

A

PRIOR ROTATION

OPPOSITE

= postrotatory nystagmus

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38
Q

What is postrotatory nystagmus ?

A
  1. Reflexive movements of the eyes after a quick rotational movement (e.g., spinning) observed to determine vestibular dysfunction.
  2. Involuntary oscillation of the eyes as a result of being rotated after stimulation of the vestibular system by spinning activities.
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39
Q

Is postrotatory nystagmus vestibular driven?

A

yes

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40
Q

The rotation of endolymph in the horizontal ______________ canals and the effects they have on the activity of the hair cells of the _______________ will be discussed later.

A

semicircular

cupula

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41
Q

What is rotatory nystagmus?

A

involuntary rotation of the eyes about the visual axis.

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42
Q

Smooth Pursuit requires an image to be moving across the:

A

field of vision.

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43
Q

Smooth pursuit movements are not under _______________________ once fixation on the image has been established.

A

volitional control

44
Q

The PPRF is involved, but the “upper motor neuron” control comes from visual signals from ____________________, channeled through an area in the _____________________, coupled with _____________________.

A

primary visual cortex

caudal temporal gyrus, coupled with
superior colliculus.

45
Q

The PPRF has a number of different types of neurons that control saccade and smooth pursuit conjugate eye movements. These can be activated through ___________________________________________or ____________________________________________.

A

reflexive pathways such as the vestibulo-ocular reflex (quick phase of nystagmus)
OR

voluntarily as in the saccades initiated from the appropriate center of Frontal Eye Fields.

46
Q

All of the systems for conjugate eye movements are influenced by __________________ through feedback information to the vestibular nuclei and then to the horizontal and/or vertical gaze centers.

A

cerebellum

47
Q

For instance, the ___________________ responds to differences in head versus eye movements and “adjusts” the __________________ of the vestibular nuclei to correct the velocity of the eye movements to match the head movements.

A

flocculus

interneurons

48
Q

The Vergence system is controlled through the ________________________ at the midbrain level.

A

reticular formation

49
Q

The _____________________ movements of the eyes are necessary for the foveation of an image as it moves _________________________.

A

disconjugate

toward or away from you.

50
Q

For ___________________, an activation of both _____________________ muscles must override the lateral rectus muscle tone to bring the eyes together.

A

convergence

medial rectus

51
Q

To overcome blurring of the image as it comes closer, this mechanism is coupled with _____________________________________________________________ for changing of focal distances.

A

pupillary constriction and accommodation (rounding of the lens)

52
Q

Cortical control of this system is located in the visual cortical areas and the vergence gaze center, an area ______________ to the horizontal gaze center. Deficits associated with horizontal or vertical gaze centers do not impair ____________________________.

A

rostral

convergence or accommodation

53
Q

SUPERIOR COLLICULUS -

A

nucleus located rostrally in the midbrain tectum (the region dorsal to the cerebral aqueduct of Sylvius).

54
Q

(Superior Colliculus) receives “upper motor neuron” fibers from the _____________ cortex (frontal eye fields - Brodmann’s area 8, ______________ lobe and caudal _____________ lobe).

A

ipsilateral

OCCIPITAL lobe and caudal TEMPORAL lobe.

55
Q

“Tectobulbar” connections to the nuclei of the cranial nerves innervating the _________________ eye muscles are a part of the pathway for ___________________________movements of the eyes, and are analogous to ___________________________ [Area 8 (Frontal Eye Fields) projects to superior colliculus].

A

extraocular

voluntary and involuntary

“upper motor neurons,”

56
Q

bulbar refers to:

A

brainstem

57
Q

Receives (tectobulbar) direct retinal projections from the optic tract via the ________________ of the superior colliculus.

A

brachium

58
Q

Descending efferent information is directed to the spinal cord and cranial nerve nuclei. The tectospinal tract crosses in the ______________ and descends to cervical spinal cord levels.

A

midbrain

59
Q

Tectospinal tract is important in the reflex _______________________________ in response to both visual and auditory cues.

A

turning of the head and neck

60
Q

PRETECTAL AREA -

A

composed of a number nuclei and located rostral to the superior colliculus.

61
Q

(Pretectal area) receives projections from the:

A

cortex, retina and superior colliculus.

62
Q

Efferents (from pretectal area) are directed to cranial nerve motor nuclei and the preganglionic parasympathetic neurons associated with _________ for reflex control of the ________________ and ________________.

A

CN III

pupil and lens

63
Q

ALL OF THE CRANIAL NERVES INVOLVED WITH MOVEMENT OF THE EYE, VOLUNTARY OR INVOLUNTARY, ARE INTERCONNECTED THROUGH AXONS TRAVELING IN THE:

A

MEDIAL LONGITUDINAL FASCICULUS (MLF).

64
Q

Abducens Nerve (CN VI) -

A

lower motor neurons innervating lateral rectus muscle.

65
Q

Abducens nerve exit the brainstem laterally adjacent to the pyramids at the:

A

pontomedullary junction.

66
Q

The abducens functions in ______________ of the eyeball.

A

abduction

67
Q

Tectobulbar fibers terminate in a __________________________, adjacent to the abducens nucleus = __________________________________________. This nucleus then projects to the abducens nucleus.

A

reticular formation nucleus

… the PARAMEDIAN PONTINE RETICULAR FORMATION (PPRF; horizontal gaze center).

68
Q

HORIZONTAL CONJUGATE GAZE [template] - internuclear neurons from the abducens nucleus (different than interneurons of PPRF) project to the _____________________________ for inhibition of _______________ lower motor neurons innervating medial rectus.

A

ipsilateral oculomotor complex

ipsilateral

69
Q

Internuclear neurons from PPRF project to the _____________________ oculomotor complex for activation of ___________________ medial rectus. These axons run in the ____________________________________.

A

contralateral

contralateral

contralateral MLF

70
Q

STRABISMUS –

A

a visible turn of one eye that may be constant. Also termed tropia (esotropia or exotropia).

71
Q

Phoria refers to the point of:

A

vergence of the eyes

72
Q

Esophoria is where the eyes are postured in __________ of the point of focus

A

front

73
Q

Exophoria is where the eyes are postured in_____________ of the point of focus.

A

back

74
Q

Myopia = or

A

(near sighted)

** different than exopheria

75
Q

hyperopia=

A

far sighted

76
Q

Myopia and hyperopia are for where the image is focused with respect to the ______________, not where the point of vergence is with respect to the _______________________________.

A

retina

object the patient is viewing

77
Q

ESOTROPIA =

A

a lesion of the abducens nerve fibers results in unopposed adduction of the ipsilateral eye.

78
Q

A lesion of the abducens nucleus (includes PPRF) results in:

A

paralysis of horizontal gaze ipsilateral to the lesion (can’t look to the side of the lesion).

79
Q

Internuclear ophthalmoplegia (MLF damaged in pons) - actions of the abducens and oculomotor nerves are:

A

uncoupled

80
Q

Excursion of the abducting eye is full, but adduction of the other eye is __________. This is the side the damage to the MLF is ___________. Abducting eye will also exhibit __________________.

A

impaired

located

pendular nystagmus

81
Q

Pendular nystagmus is thought to be due to loss of

A

inhibitory fibers in MLF.

82
Q

Trochlear Nerve (CN IV) -

A

lower motor neurons innervating the contralateral superior oblique muscle.

83
Q

The axons of this nerve (CN IV) course dorsally around the:

A

periaqueductal grey and decussate.

84
Q

The nerve (CN IV) then courses around the brainstem to occupy a position ___________ to the oculomotor nerve between the ________________________________

A

lateral

superior cerebellar and posterior cerebral arteries.

85
Q

CN IV functions in _______________ and _______________ of the eyeball.

A

rotation and

depression

86
Q

Lesion of the trochlear nerve (RARE) is marked by an inability to:

A

look down and thus problems walking down stairs.

87
Q

Vertical gaze is also coordinated through a vertical gaze center (Interstitial nucleus of ____________; located near ____________ nucleus)

A

Cajal

trochlear

88
Q

Oculomotor Nerve (CN III) -

A

lower motor neurons for the remainder of the extraocular eye muscles and levator palpebrae superioris, all ipsilateral, (except to superior rectus).

89
Q

CN III also contains:

A

preganglionic parasympathetic fibers to the ciliary ganglia.

90
Q

The oculomotor nuclear complex is divided into individual cell groups responsible for the innervation of each _____________.

A

muscle

91
Q

The preganglionic parasympathetic cell bodies lie in an ________________ nucleus, the ________________________ nucleus.

A

adjacent

Edinger Westphal

92
Q

All of the fibers from these nuclei traverse the ______________ near the ________________ and cross the _________________ to exit in the _________________ fossa. The nerve can be seen exiting between the superior cerebellar and posterior cerebral arteries.

A

tegmentum

red nucleus

cerebral peduncles

interpeduncular

93
Q

EXOTROPIA -

A

a lesion of the oculomotor nerve.

94
Q

Oculomotor palsy, causes:

A

paralysis of all extraocular eye muscles except LR and SO, and results in unopposed abduction of the ipsilateral eye.

95
Q

Drooping of the eyelid is also noted (in oculomotor palsy) due to the involvement of __________________________________.

A

levator palpebrae superioris

96
Q

Loss of parasympathetic innervation of the ciliary ganglia results in:

A

dilation (mydriasis) of the pupil.

97
Q

Horizontal conjugate gaze, volitional or pursuit:

A
  • paralysis of volitional horizontal conjugate gaze

- internuclear ophthalmoplegia

98
Q

Fixation and convergence -

A

Accommodation reflex.

***REVIEW the pathway for this reflex.

99
Q

Pupillary light reflex (this reflex and testing for its integrity) requires an intact

A

optic nerve and tract.

**See figure at end of handout.

100
Q

Argyll-Robertson pupil: Seen in tertiary syphilis. The pupil is ________________________________________ Will
_______________ in accommodation associated with convergence.

A

small in dim light and non-reactive to light.

constrict

101
Q

2 Alternating hemiplegias =

A
  1. Abducens or middle alternating hemiplegia

2. Oculomotor or superior alternating hemiplegia

102
Q

Horner’s Syndrome -

A

lesion of sympathetic nervous system pathway; descending influence from the hypothalamus directed to preganglionic sympathetic neurons in the spinal cord, or any of the peripheral pathways carrying sympathetic fibers.

103
Q

In Horner’s syndrome, if that involvement is to sympathetics directed to the head (ascending sympathetic chain, superior cervical ganglion), the clinical manifestation in the face is as follows (4):

A
  • ptosis
  • miosis
  • dry skin
  • flushed skin
104
Q

ptosis =

A

due to loss of sympathetic innervation to superior tarsal muscle of the eyelid and its control by levator palpebrae superioris

105
Q

miosis =

A

(pupil constricted) - loss of dilator control; unopposed constrictor tone (parasympathetic).

106
Q

dry skin =

A

(absence of sweating) - loss of sympathetic control of sweat glands

107
Q

flushed skin =

A

lack of constriction of capillary field

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