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Neuro (Exam 3) > Vision Tracts > Flashcards

Vision Tracts Flashcards

1
Q

How are visual system lesions described?

A

In terms of their visual field deficits

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2
Q

What happens to an image on the retina?

A

Inverted both laterally and vertically

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3
Q

How do the two optic nerves decussate?

A

The nasal half of each retina goes to the contralateral optic tract.
The temporal half of each retina goes to the ipsilateral optic tract.

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4
Q

What is the optic tract made up of?

A

Fibers from temporal retina (ipsilaterally) and nasal retina (contralaterally)

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5
Q

What is the tract for vision (up to brain)?

A

Optic nerve – Optic chiasm – Optic tract (through cerebral peduncle) – lateral geniculate nucleus

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6
Q

What is the ventral base of LGN made up of?

A

Incoming optic tract (retinogeniculate) fibers

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7
Q

What is the dorsal border of LGN made up of?

A

Outgoing optic radiations

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8
Q

Magnocellular layers

A
  • From layers 1,2
  • Ganglion cell inputs from rods – larger RFs (thick/rapidly conducting axons)
  • Sensitive to moving stimuli
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9
Q

Parvocellular layers

A
  • Layers 3-6
  • Ganglion cells inputs from cones – small RF (slow conducting axons)
  • Stationary stimuli
  • High-acuity color vision
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10
Q

Where do ganglion cells from the temporal retina terminate?

A
  • Travel uncrossed and terminate @ layers 2,3,5 of ipsilateral LGN
  • Temporal VFs
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11
Q

Where do ganglion cells from the nasal retina terminate?

A
  • Cross and terminate @ layers 1,4,6 of contralateral LGN

- Nasal VFs

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12
Q

Describe right visual field tracts

A 
Nasal retina (R) goes to layers 1,4,6 of Left LGN 
Temporal retina (R) goes to layers 2,3,5 of R LGN
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13
Q

How is each point represented 6 times?

A

Optic tract axons branch into multiple layers even though they’re from the same vision field

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14
Q

Where do fibers from the lower quadrant of CL hemifield go?

A
  • Originate from dorsomedial portion of LGN
  • Pass through retrolenticular limb of int. capsule
  • Terminate @ superior bank of calcarine sulcus (cuneus)
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15
Q

Where do fibers from the upper quadrant of CL hemifield go?

A
  • Originate from ventrolateral portion of LGN
  • Arch rostrally, going into white matter of temporal lobe and forming Meyer loop
  • Terminate @ inferior bank of calcarine sulcus (lingual gyrus)
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16
Q

Where do fibers from the macula and fovea go?

A
  • Originate from central regions of LGN and pass caudally on the visual cortex
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17
Q

What would a lesion to the temporal lobe cause?

A

Superior visual field deficit @ Meyer’s loop

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18
Q

Representation of macula in visual cortex?

A
  • Disproportionately large and posteriorly (@ the occipital pole)
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19
Q

What is responsible for depth perception?

A

Combination of images from both eyes

20
Q

What “area” is the calcarine sulcus?

A

Broadmann area 17

21
Q

What areas correspond with the visual association cortex?

A

Broadmann areas 18 and 19
(temporal and parietal lobes)
*parieto-occipito-temporal areas

22
Q

Role of superior colliculus in vision?

A
  • Spatially directs head movements and visual reflexes
  • Fibers pass over the medial geniculate nucleus in the brachium of superior colliculus and terminate in sup. colliculus
  • Directs eye movements
23
Q

Role of pretectum area in vision?

A
  • Bilateral group of nuclei near midbrain/forebrain jxn
  • Respond to pretectal nuclei respond to varying intensities of illuminance
  • Pupillary light reflex
24
Q

Innervation for pupillary dilator m.

A

Sympathetic postganglionic fibers (from superior cervical ganglion)

25
Q

Innervation for pupillary constrictor m.

A

Parasympathetic postganglionic fibers (Edinger- Westphal nucleus)

26
Q

Pupillary constriction pathway

A
  1. Retinal axons terminate @ olivary pretectal nucleus (pretectum)
  2. Bilateral projections to EW nucleus (preganglionic) (CL travel via post. commissure)
  3. PS exit w/ CN III and synapse @ IL ciliary ganglion
  4. Postganglionic fibers (short ciliary nn.) excite pupillary constrictor m.
27
Q

Lesion of CN III/loss of preganglionic fibers…

A

IL mydriasis (pupillary dilaton) and paralysis of accommodation

28
Q

Lesion of CN III post ganglionic fibers…

A

Tonic dilated pupil

29
Q

Partial lesion of CN II…

A
  • Diminished direct/consensual responses when light shined into IL eye
  • Normal response when shined into CL eye
30
Q

Total lesion of CN II…

A
  • Blind eye – when light shined into IL eye, there is no direct or consensual response
31
Q

Lesion @ optic tract or pretectum…

A

Weakened (but not lost) responses

32
Q

Large lesion @ post. midbrain

A

Weakened response bilaterally

33
Q

Lesions @ CN III or nucleus

A

Both direct/consensual response lost IL (present CL)

34
Q

Damage anterior to chiasm?

A

Only IL eye affected

35
Q

Damage @ chiasm?

A

Heteronymous deficits

36
Q

Damage behind chiasm?

A

Homonymous deficits

37
Q

Lesion of CN II

A

Total loss of vision in affected eye

38
Q

Lesion @ optic chiasm?

A

Non-homonymous bitemporal hemianopia

39
Q

Lesion @ optic tract?

A

CL homonymous hemianopia

40
Q

R. Lesion @ temporal lobe (aka Meyer’s loop)

A

Superior left homonymous quadrantanopia (pie in sky)

41
Q

R. Lesion @ parietal lobe

A

Inferior left homonymous quadrantanopia (pie in floor)

42
Q

R. Lesion @ geniculocalcarine tract

A

CL left homonymous hemianopia

43
Q

R. Lesion @ inferior bank of calcarine fissure

A

Superior left homonymous quadrantanopia (w/ macular sparing)

44
Q

R. Lesion @ superior bank of calcarine fissure

A

Inferior left homonymous quadrantanopia (w/ macular sparing)

45
Q

R. Lesion @ both banks of calcarine fissure

A

CL left homonymous hemianopia (w/ macular sparing)

Neuro (Exam 3) (15 decks)

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