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► Med - Year 1 > Oculomotor System > Flashcards

Oculomotor System Flashcards

1
Q

What three crossings insure consensual response of the pupil? (for constriction)

A
  1. Optic chiasm
  2. Pretectal olivary nuclei to contralateral edinger-westphal nucleus (via posterior commissure)
  3. Pretectal olivary nuclei to ipsi- and contra-lateral edinger westphal nuclei
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2
Q

In the retina, photons are converted to electrical impulses by what type of cells?

A

melanopsin-containing retinal ganglion cells

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3
Q

10-15% of optic tract fibers by pass what nucleus that heads to the cerebral cortex?

A

Lateral geniculate nucleus

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4
Q

The 10-15% of fibers that don’t go to the cerebral cortex instead target what region? Via the ____ of the ______

A

Target pretectum via the brachium of the superior colliculus

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5
Q

Once fibers reach the pre-tectum, they synapse on the pretectum olivary cell nucleus and go these two separate ways:

A
  • EW nuclei on opposite side

- EW nuclei on same side (both ipsi and contra)

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6
Q

Parasympathetic fibers from Edinger-Westphal travel with what nerve? Synapse where?

A

Oculomotor nerve (III), ciliary gnaglion

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7
Q

Short ciliary fibers reach what muscles?

A

Pupil constrictor muscles

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8
Q

The pathway from EW nucleus to pupillary constrictor muscles is (efferent/afferent)

A

Efferent

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9
Q

The pathway from retinal ganlgion cells to the pretectum (just in front of midbrain) is (efferent/afferent)

A

Afferent

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10
Q

In the dark, normal eyes are (constricted/dilated)

A

dilated in dark, to help you see better

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11
Q

The usual pupillary response to direct light is that both pupils will (contract/dilate) equally if nothing is wrong with either pupil

A

Contract

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12
Q

If you move the light quickly from one eye to the other if nothing is wrong with them, what should happen?

A

both pupils should hold their level of contraction

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13
Q

In an injured optic nerve (before chiasm, just posterior to eyeball), will it transmit light?

A

Yes, but to a lesser and slower degree

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14
Q

In an injured optic nerve, what happens when you shine a flashlight?

A

Injured nerve will still transmit light but just slower, so when light is moved from good to bad eye, the brain interprets this as a decrease of light being presented. brain will dilate both pupils to let in more light. Dilation response is in both eyes, despite only one eye being affected

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15
Q

RAPD stands for

A

relative afferent pupillary defect

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16
Q

the physiological basis of RAPD test is that, in health eyes, a bright light shone in one eye leads to a constriction of (one/both) pupils

A

both, equal constriction

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17
Q

What does a positive RAPD mean?

A

there is a difference between the two eyes in the afferent pathway due to retinal or optic nerve disease (when light is shone into normal eye, both pupils will constrict further, because can sense the light better)

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18
Q

In pupillary dilation, the first order neuron originates from where?

A

Posterior-lateral hypothalamus

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19
Q

In pupillary dilation, the first order neuron synapses where?

A

In the intermedio-lateral cell column cervical spinal cord (C7-T3)

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20
Q

This is the preganglionic sympathetic outflow nerve tract from the spinal cord

A

white ramus

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21
Q

After synapsing in the intermediolateral cell column, the second order neuron for pupillary dilation exits the spinal cord via what to head where??

A

White ramie in C8-T3 ventral roots to the paravertebral sympathetic column

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22
Q

The second order neurons for pupillary constriction ascent along what arteries and synapse where?

A

Ascend along carotid arteries, synapse in the superior cervical ganglion

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23
Q

3rd order neuron for pupillary constriction reach what division of the trigeminal nerve?

A

opthalmic

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24
Q

From the superior cervical ganglion, what type of fibers ascend along the internal carotid artery?

A

Noradrenergic fibers (norepinephrine)

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25
Q

3rd order neurons for pupillary constriction pass through what fissure and merge with what branches?

A

Superior orbital fissue, long ciliary nerves (branches of nasociliary nerve)

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26
Q

3rd order ganglion neurons for pupillary constriction innervate what three muscles?

A

Pupillary dilater, and superior and inferior tarsal muscles

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27
Q

Do sympathetic fibers synapse in the ciliary ganglion?

A

No, they just pass through

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28
Q

What fibers leave before entering skull for pupillary constriction?

A

Sudomotor fibers to sweat glands

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29
Q

In Horner’s syndrome, there can be lesion to what order neuron?

A

all 3.

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30
Q

3 symptoms of Horner’s + congenital symptom

A
  1. Ptosis (eyelid drooping)
  2. Miosis (pupil constriction)
  3. Anhydrosis
  4. Heterochromia (with affected eye being hypopigmented)
31
Q

Term for fast movement of the eye

A

Saccade

32
Q

What mediates the “yoking” of eyes?

A

Median Longitudinal Fasciculus (MLF)

33
Q

Saccades are ___

A

conjugate

34
Q

Where is the horizontal gaze center located?

A

PPRF - paramedian portion of pontine reticular formation

35
Q

As eye position moves, saccude in the pulling direction of muscles produces a burst of discharge cells from?

A

Abducens nucleus

36
Q

Discharge of what nucleus provides the tonic activity?

A

nPH-nucleus prepositus hypoglossi

37
Q

Where is the burst generated?

A

PPRF (paramedian pontine reticular formation)

38
Q

discharge in abducens nucleus = _____ + ______

A

nPH + PPRF

39
Q

Pause neurons in _____ inhibit PPRF burst neurons

A

Raphe interpositus (RIP)

40
Q

Omnipause

A

When RIP neurons stop firing just before and for the duration of saccades (to generate burst)

41
Q

When do RIP neurons resume their tonic discharge?

A

Just before saccade end

42
Q

Role of pause neurons in the RIP

A

inhibit PPRF burst neurons (raphe interpositius)

43
Q

What specifically in the nucleus preopositus hypoglossi (nPH) change the burst into a new tonic level of activity?

A

Neural integrator (NI)

44
Q

Saccades are controlled by what neurons?

A

PPRF burst neurons

45
Q

What provide the burst of activity?

A

PPRF

46
Q

What receives PPRF projections?

A

Abducens and nPH

47
Q

What provides the tonic level of activity?

A

nPH

48
Q

Where do nPH and PPRF get summed together?

A

abducens

49
Q

What enforces eye conjugacy?

A

MLF

50
Q

MLF couples what to regions of brainstem together?

A

Pons (abducens) to midbrain (oculomotor)

51
Q

Projections of internuclear neurons of the abducens cross the midline to ascend in the MLF to what nucleus to innervate what muscle?

A

Oculomotor nucleus to innervate the medial rectus muscles

52
Q

Why is the MLF necessary for conjugacy?

A

There is no direct projections from the PPRf to the medial rectus motorneurons in the oculomotor nucleus

53
Q

The MLF connects ___ nerve to ___nucleus

A

abducens nerve to oculomotor nucleus

54
Q

Vergence

A

movement of eyes in opposite directions in response to disparity or accomodation

55
Q

accomodation

A

lens changing

56
Q

disparity

A

image closer or further from fixation point is blured

57
Q

The “near triad”

A
  • vergence
  • accommodation
  • pupillary constriction (to look at near object)
58
Q

Vergence has indirect and direct pathways, that specifically dont involve what?

A

they do not involve the conjugate pathway (separate system from conjugate eye movement)

59
Q

Vergence is mediated by direct and indirect pathways, which are directed to this region

A

SOA: supra-oculomotor region

SOA to medial rectus motoneurons (bilaterally) and tot he EW nuclei

60
Q

In a patient with an MLF lesion, is vergence conserved?

A

YES

61
Q

Ocular motility after MLF lesion (4)

A
  1. mild extropia (wall-eyed gaze, eyes deviated outward due to lack of medial rectus muscle innervation)
  2. Loss of adduction of ipsilateral eye
  3. Abducting nystagmus of the eye contralateral to the lesion on gaze left
  4. preserved convergence
62
Q

Do oculomotor nerve lesions demonstrate loss of convergence?

A

YES

63
Q

How can you distinguish between MLF lesion and 3rd nerve palsy?

A

Based on vergence–if they cannot converge, then you know its oculomotor problem

64
Q

In addition to loss of convergence, a 3rd nerve lesion produce a loss of what symptoms? (2)

A
  1. Loss of adduction of ipsilateral eye
  2. may also include pupillary dilation and severe ptosis of same lid (bc CN III carries parasympathetic fibers to constrict pupil and sympathetic fibers to the tarsal muscles that raise eyelid)
65
Q

Occiptal cortex projects to these two primary eye movement regions:

A
  1. Inferior parietal lobule

2. Frontal eye fields

66
Q

Signals from the frontal eye fields (FEF) and parietal lobe descend to the brain stem via what pathway

A

Cortical-Collicular pathway

67
Q

In the cortical-collicular pathway, what is the target?

A

Superior colliculus, the paramedium zone of the pontine reticular formation (PPRF) and the riMLF

68
Q

Which region in cortex relies on superior colliculus?

A

Parietal. Left parietal goes to left colliculus, but then they cross and go to opposite PPRF. Frontal eye fields bypass the superior colliculus and reach PPRF (some go into colliculus)

69
Q

Frontal eye fields provide these three things:

A
  1. voluntary control
  2. spatial memory
  3. select the visual target of a saccade
70
Q

FEF can use the superior colliculus or go directly where?

A

To horizontal and vertical gaze center

71
Q

Parietal cortex provides what to the contralateral sensorium?

A

attention (visual auditory, and somatosensory)

72
Q

Is parietal cortex collicular dependent?

A

Yes

73
Q

Acute frontal lobe lesions produce a “gaze preference” (toward/away from) the side of lesion and (contralateral/ipsilateral) hemiparesis

A

toward side of lesion, contralateral hemiparesis (weakness)

74
Q

Apraxia of eye movement is due to what type of lesion?

A

Bilateral fronto-parietal lesions

► Med - Year 1 (48 decks)

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