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NS-1 > Visual Tracts > Flashcards

Visual Tracts Flashcards

1
Q

What is the difference btw the visual field and the retinal field?

A

Visual field = area that persion is able to see when eyes are fixed

image on retina = retinal field

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2
Q

Where is the blind spot?

A

where optic disc is = no photoreceptors here

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3
Q

What are the fovea centralis and macula lutea?

A

object of attention = fovea centralis

macula lutea is surrounding 1 cm

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4
Q

What are the subdivisions of the visual field?

A

binocular zone: central region seen by both eyes

Monocular zone: edges, seen only by one eye

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5
Q

What are the subdivisions of the retinal fields?

A

nasal and temporal hemifields

upper and lower quadrants

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6
Q

which parts of the optic nerve decussate in the optic chiasm?

A

nasal half of each retina –> goes to contra optic tract

temporal half of each retina –> ipsi optic tract

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7
Q

What is the purpose of partial decussation of the optic nerves?

A

creates depth perception

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8
Q

Where does the optic tract synapse?

A

curves posteriorly around cerebral peduncle –> terminates in lateral geniculate nucleus (LGN)

in precise retinotopic pattern

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9
Q

What forms the ventral and dorsal borders of the LGN?

A

ventral = optic tract fibers

dorsal and lateral borders = outgoing optic radiations

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10
Q

What are the magnocellular layers of the LGN?

A

layers 1 and 2 (dorsal)

large cells

receive ganglion cell inputs relayed from rods

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11
Q

What are the parvocellular layers of the LGN?

A

layers 3-6 (dorsal)

small cells

receive input from cones

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12
Q

Where do temporal retinal fibers terminate?

A

remain uncrossed –> terminate in layers 2,3, and 5 of ipsi LGN

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13
Q

Where do nasal retinal fibers terminate?

A

cross –> contra layers 1, 4, and 6 of LGN

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14
Q

How many times is the same point in the visual field represented?

A

6 times

once in each layer of the LGN

bc optic tract axons branch in multiple layers even though they’re from the same visual field

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15
Q

What is the optic radiation?

A

secondary neurons from LGN –> to primary visual cortex in calcarine sulcus

myelinated

retinotopic organization is maintained, but ind fibers carry info from one eye

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16
Q

Where is the primary visual cortex?

A

upper and lower banks of the calcarine sulcus

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17
Q

How are optic radiations divided?

A
  1. from lower quadrant of contra hemifield –> thru retrolenticular limb of internal capule –> to superior bank of calcarine sulcus = cuneus
  2. from upper quad of contra hemifield –> pass thru temporal lobe –> inferior bank of calcarine sulcus = lingual gyrus
  3. from macula and fovia –> pass to caudal parts of visual cortex
18
Q

why can temporal lobe damage cause superior visual field deficit?

A

bc fibers from contra upper quad pass thru temporal lobe on way to visual cortex = meyer loop

19
Q

How is macula represented in the LGN and visual cortex?

A

in disporportionately large volumes

most posteriorly in region of occipital pole

20
Q

What is Brodmann’s area 17?

A

the primary visual cortex

21
Q

Why is the primary visual cortex called the striate cortex?

A

bc you can see numerous myelinated fibers w/in a discrete layer –> striped appearance

22
Q

What surrounds the striate cortex and what does it do?

A

areas 18 and 19

this + related parts of temporal and parietal lobes = visual association cortex

parieto-occipito-temporal area

helps interpret location, motion, form color

23
Q

What does the superior colliculus do in vision?

A

spatially directs head movements and visual reflexes

retinal input –> bypasses LGN –> brachium of superior colliculus

cortical input: from area 17 –> brachium –> superior colliculus

24
Q

What does the pretectal area do in vision?

A

bilateral grp of interconnected nuclei near midbrain/forebrain jxn

input from afferent bilateral fibers from optic tract; LGN and suprachiasmatic nucleus

respond to varying intensities of light –> mediate pupillary light reflex

25
Q

What ANS parts innervate pupillary constrictor and dilator ms?

A

Sympathetics from superior cervical ganglion –> pupillary dilator m

PS from edinger-westphal –> ciliary ganglion –> short ciliary ns –> pupillary contrictor m

26
Q

How does the pupillary reflex occur?

A

4 neurons:

retinal axons terminate in olivary pretectal nucleus –>

bilateral projections to edinger-westphal preganglionic nucleus –>

PS exit w/ CN 3 –> ipsi ciliary ganglion –> short ciliary Ns –> pupillary constrictor

27
Q

What is hemianopia?

A

blindness in 1/2 of visual field

28
Q

Quadrantoanopia

A

blindenss of a quadrant of the visual field

29
Q

Homonymous visual fields

A

conditions in visual field losses are similar in both eyes

30
Q

Heteronymous visual fields

A

conditions in which the two eyes have non-overlapping field losses

31
Q

Macular sparing

A

visual field loss that preserves vision in center of visual field

32
Q

Congruous deficit

A

symmetrical - can be superimposed on other eye

colser a lesion is to the cortex, more likely to be congruous

33
Q

What does damage anterior to the chiasm cause?

A

damage only to the ipsi eye

34
Q

What does damage at the ciasm cause?

A

heteronymous deficits

bitemporal hemianopia

(in rare cases Left hemianopia, right eye)

35
Q

What does damage behind the chiasm cause?

A

homonymous deficits

36
Q

What is associative visual agnosia?

A

pt cannot name or describe an object in the visual field, but he can recognize and demonstrate its use

infarction of the left occipital lobe and posterior corpus callosum - typically bc of occlusion of PCA

disconnect btw language area from visually association cortex

may also be alexic and writing ability may be affected

37
Q

What would damage to the right optic tract cause?

A

left homonymous hemianopia

(blind in left upper corner in both eyes)

38
Q

What would damage to the right meyer loop cause?

A

left superior quadrantanopia

(blind in left upper quadrant in both eyes)

39
Q

What would damage to both optic radiations on the right cause?

A

left homonymous hemianopia

(blind in left half of each eye’s field of vision)

40
Q

What would damage to the right superior optic radiations cause?

A

left inferior quadrantanopia

(blind in left lower quadrant of each eye)

41
Q

What would damage to the right inferior optic radiations cause?

A

left superior quadrantanopia

(blind in left upper quadrant in each eye)

NS-1 (50 decks)

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