Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Neuroscience III > Oculomotor Mechanisms > Flashcards

Oculomotor Mechanisms Flashcards

(80 cards)

Start Studying
1
Q

List some symptoms of oculomotor disturbances:

A
  1. blurred vision
  2. diploplia
  3. oscillopsia
  4. vertigo
  5. dysequilibrium/falls
  6. brainstem related symptoms (dysphagia or dystarthria, cerebellar signs, tinnitus or hearing loss)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

The oculomotor nucleus is located in the:

A

rostral midbrain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The oculomotor nerve innervates ______ except these two:

A

all extraocular muscles

except lateral rectus and superior oblique

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the resting position with CN III lesion:

A

exotropia (lateral strabismus)
ptosis (drooping)
diploplia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Which motor components are impaired with CN III lesion?

A

no upward gaze

no medial gaze ipsilaterally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

The pupillary light reflex tests which CN’s?

A

CN II and III

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The pupillary light reflex tests integrate of connection between ___ and ___ via the ___.

A

retina and midbrain via the thalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Pupillary dilation and dec. pupillary light reflex is an important indicator of:

A

increased intracranial pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the direct effect and consensual response to pupillary light reflex:

A

direct: shine light - pupil constricts
consensual: contralateral pupil also constricts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the circuit for direct pupillary response:

A

(sensory) retina > optic nerve > optic tract >pretectum > CN III (motor)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the circuit for consensual pupillary response:

A

fibers cross in pretectum to contralateral CN III

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The trochlear nerve nucleus is located in:

A

caudal midbrain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Trochlear nerve innervates:

A

superior oblique muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the resting position with CN IV lesion:

A

no apparent drift
maybe hypertropia (elevated) and extrusion
maybe diploplia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Which motor components are impaired with CN IV lesion?

A

no gaze down when adducted ipsilateral to lesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How is CN IV tested?

A

pt. follows examiner’s finger medially and then downward (testing superior oblique muscle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Abducens, CN VI, is located in:

A

caudal pons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Abducens, CN VI, innervates:

A

lateral rectus muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe the resting position with CN VI lesion:

A

esotropia (medial strabismus)

diploplia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which motor components are impaired with CN VI lesion?

A

inability to gaze laterally on ipsilateral side of lesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Define conjugate eye mvmnt:

A

both eyes look same way (i.e.: both to R/L/up/down)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Define horizontal conjugate gaze:

A

Coordination that requires one eye to adduct while the other abducts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

The fiber bundle medial to abducens nucleus bilaterally is:

A

medial longitudinal fasciculus (MLF)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

The medial longitudinal fasciculus carries fivers that interconnect with:

A

CN VI
contralateral CN III nuclei
vestibular nuclei

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
With damage to adbucens nucleus, resting position is ______; the mvmnt deficit is:
rests in medial strabismus | lateral gaze paralysis (no lateral gaze from either eye toward the side of lesion)
26
Fibers in the MLF are axons of internuclear neurons of ____ nerve that project to and excite:
abducens | excite contralateral oculomotor motor neurons
27
Internuclear opthalmoplegia (INO) is a lesion of:
just the MLF between CN III and IV
28
With INO, the position at rest is _____; the mvmnt deficit is:
no drift | no ipsilateral eye adduction with lateral gaze to contralateral side of lesion
29
What is vertical conjugate gaze? What nerve and muscles produce the movement?
upward/downward/torsional gazes | produces by CN III nucleus innervating superior/inferior rectus bilaterally
30
Keeping an image centered on the fovea requires:
fxnal LMN's of CN III, IV, IV plus CNS mechanisms
31
Impairments of gaze fixation in the primary position (straight ahead) may be:
resting nystagmus saccadic intorsions ocular flutter
32
What is gaze fixation?
ability to hold eyes in fixed position to maintain steady visual target on fovea
33
Which areas are involved in regulating gaze fixation?
cortex and brainstem (vestibular, cerebellum)
34
At the end of eye movement, gaze must be fixated on target. This process is called:
step command | from "neural integrator"
35
The neural integrator for horizontal eye mvmnts:
medial vestibular nucleus and nucleus prepositus hypoglossi in MEDULLA
36
The neural integrator for vertical eye mvmnts:
interstitial nucleus of Cajal in MIDBRAIN
37
Vest-Cb (flocculus) takes into account these qualities of eye mvmnts: In order to:
velocity and amplitude of eye mvmnts from cortex and through neural integrator, then generates gaze fixation at new, eccentric eye position
38
VOR fxn:
maintain visual target on fovea while head is moving through smooth high velocity eye mvmnts in equal/opposite directions to head motion
39
VOR mechanism speed and latency:
generates eye mvmnt up to 400 degrees/second; shortest latency reflex in body at ~10ms latency
40
VOR involves receptors in the:
inner ear, vesitubular nuclei, and connections to eye mvmnt nuclei through MLF
41
What region coordinates amplitude and adaptation of VOR?
Vest-Cb
42
Describe optokinetic nystagmus:
a "normal" nystagmus that allows for stabilization of a series of moving visual targets on the fovea (i.e.: watching telephone poles go by); requires both slow and fast rhythmical eye mvmnts
43
What structures allow for fxn of optokinetic nystagmus?
cortical mechanisms initiate | brainstem smooth pursuit mechanisms are important
44
Slow rhythmical eye mvmnt for tracking or maintaining moving visual target on fovea is called:
smooth pursuit
45
Fast rhythmical eye mvmnt for repositioning is called:
saccade (can be voluntary or reflexive)
46
Saccades are recruited when moving from one visual target to another or if target velocity is > ___.
60 degrees/sec
47
Saccades are quick jerks with velocities of:
250-600 degrees/sec
48
Describe the 2 components to saccades:
1. PULSE SIGNAL: to move eye to new position | 2. STEP COMMAND: to hold eye in new position (gaze fixation mechs via neural integrator)
49
Describe the mechanism for horizontal saccades:
1. initiated by cortical area 8/frontal eye field 2. contra. paramedian pontine RF of pons 3. ipsi CN III, CN VI nucleus, MLF 4. once eyes reach target, step command generated via neural integrator
50
Damage to frontal eye field results in:
inability to initiate saccages to contra. side; gaze preference is towards same side of cortical lesion
51
Damage to pons results in:
inability to generate saccades to ipsi. side; gaze preference is away from side of lesion
52
In order for vertical saccades to be affected, what must occur?
bilateral damage
53
Describe the mechanism for vertical saccades:
1. frontal eye field 2. midbrain 3. interstitial nucleus of canal 4. B CN III and IV nuclei
54
What is the alternate pathway for voluntary saccades?
basal ganglia to superior colliculus
55
What structure regulates the amplitude of saccades?
cerebellar vermis
56
Reflexive saccades (orienting behavior) involve ____ projecting to the:
subcortical projection to the superior colliculus
57
Do reflexive saccades require involvement of the cortex?
NO! the retina are directly to superior colliculus
58
Words used to document the quality of impaired saccades include:
slow hypermetric hypometric
59
When is smooth pursuit used?
when head is still and target velocities < 60 degrees/sec
60
Information on velocity and trajectory of target in smooth pursuit are registered through:
visual system | Cerebral cortex: frontal eye field, parietal, temporal and occipital visual association areas
61
Information on velocity and trajectory of target in smooth pursuit are registered through visual system then projected to:
Cb (vermis and flocculus) and medial vestibular nucleus
62
Smooth pursuit eye mvmnts are generated via:
1. medial vestibular 2. abducens nuclues 3. MLF for conjugate gaze
63
Abnormal smooth pursuit may include:
corrective saccades
64
impaired smooth pursuit is a sign of:
pathology of CNS | but difficult to locate the lesion without other signs
65
Describe vergence:
aka accommodation | parasympathetic reflex involving near focus and pupillary constriction
66
Describe the pathway in vergence:
1. visual assoc. cortex 2. midbrain (pretectum) 3. B oculomotor nuclei
67
Nystagmus is named by the direction of:
fast (saccadic) component
68
How many different kinds of nystagmus exist?
60; useful in diagnosing certain disorders
69
Nystagmus is a symptom in these types of disorders:
vestibular disorders cerebellar disorders other brainstem lesions
70
T or F: Some types of nystagmus are normal
True
71
4 types of Physiologic (normal) Nystagmus
1. optokinetic (voluntary eye mvmnts) 2. rotational induced 3. Caloric induced (COWS) 4. end range
72
When do you see rotational-induced nystagmus?
When they've been passively spun around. Fast phase is in direction of spin.
73
Caloric Induced (COWS)
Caloric testing (H2O in ear canals) artificially induces flow of endolymph in semicircular canals, causing nystagmus.
74
What eye ROM can cause end-range nystagmus?
> 30 degrees
75
Pathological Nystagmus types
1. Spontaneous 2. Gaze-evoked 3. Congenital 4. Positional
76
When do you see spontaneous nystagmus?
At rest. ALWAYS CNS pathology.
77
What must you differentiate Gaze-evoked nystagmus from?
normal end range nytagmus
78
What brings on Positional Nystagmus?
Change in head position. Seen in BPPV
79
Which nystagmuses are always signs of Central pathology?
Vertical, pure torsional, and direction changing nystagmus
80
Which nystagmuses will diminish over time?
Peripheral nystagmus, because of central compensating mechaisms.

Neuroscience III (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions