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Human basic neuroscience > Visual Tracts > Flashcards

Visual Tracts Flashcards

1
Q

What forms the visual pathway?

A

axons of ganglion cells and the axons of higher order cells on which they synapse

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2
Q

what type of arrangement does the visual pathway maintain at easy relay location?

A

retinotopic

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3
Q

what are the three layers of the eye?

A

fibrous layer, vascular layer, retina

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4
Q

what does the fibrous layer of the eye consist of?

A

the sclera and the cornea

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5
Q

what does the vascular layer of the eye consist of?

A

choroid, ciliary body, and the iris

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6
Q

what is the role of the sclera?

A

it is an external layer of the eyeball that protects internal structures and provides sites for muscle insertion

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7
Q

what type of tissue makes up the sclera?

A

dense regular CT with flat bundles of type I collagen

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8
Q

what are the five distinct layers of the cornea?

A

corneal epithelium, anterior limiting membrane (bowman membrane), stroma, posterior limiting membrane (descemet’s membrane) and the inner endothelium

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9
Q

what type of tissue makes up the corneal epithelium?

A

nonkaratinized stratified squamous epithelium

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10
Q

what separates the corneal epithelium from the stroma?

A

the anterior limiting membrane (Bowman membrane)

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11
Q

what makes up the stroma?

A

keratocytes

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12
Q

what separates the stroma from the inner endothelium?

A

the posterior limiting membrane (Descemet’s membrane)

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13
Q

what is the transitional area where the transparent cornea merges with the opaque sclera?

A

limbus

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14
Q

what does the limbus denote?

A

the end of Bowman’s area and the beginning of the conjunctiva

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15
Q

what cell population is found at the surface of the limbus and what is their role?

A

epithelial stem cells- give rise to progenitor cells that move into the corneal epithelium

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16
Q

what is the middle layer of the eye?

A

the vascular layer

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17
Q

what does the choroid consist of?

A

loose, well-vascularized connective tissue and melanocytes

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18
Q

what is the role of the melanocytes found in the choroid of the eye?

A

it prevents light from entering the eye except via the pupil

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19
Q

what is the Bruch’s membrane?

A

it is a thin extracellular sheet that includes the basal lamina of the retina’s pigmented layer (more anterior membrane)

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20
Q

what is the innermost layer of the eye?

A

the retina

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21
Q

what are the two layers of the retina?

A
  1. outer pigmented layer and 2. inner neural layer
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22
Q

what does the retina develop from?

A

the optic cup

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23
Q

what is the tissue that makes up the outer pigmented layer of the retina?

A

simple cuboidal epithelium

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24
Q

what makes up the inner neural layer of the retina?

A

it is stratified with various neurons and photoreceptors

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25
Q

the neural component of the retina extends to where?

A

anteriorly to the ora serrata

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26
Q

what are some of the functions of the pigmented epithelium layer of the retina?

A

it absorbs scattered light, forms part of the blood-retina barrier, isomerizes all-trans-retinal–> 11-cis-retinal, phagocytosis, removes free radicals and secretes ATP

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27
Q

what is the most posterior layer of the retina/ the layer closest to the choroid?

A

the pigmented epithelium

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28
Q

what are the layers of the neural retina, starting from the most superficial?

A

inner limiting membrane, nerve fiber layer, ganglionic layer, inner plexiform layer, inner nuclear layer, outer plexiform layer, outer nuclear layer, outer limiting layer, rod and cone layer, pigmented layer

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29
Q

what makes up the inner limiting membrane (layer 1 of the neural retina)?

A

it is a basement membrane covered by processes of Muller cells

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30
Q

what is contained within the nerve fiber layer (layer 2) of the the neural retina?

A

ganglionic cell axons

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31
Q

where do the ganglionic cell axons from layer 2 of the neural retina converge and what do they form?

A

they converge at the optic disc and they form CN II

32
Q

what does the ganglionic layer (layer 3) of the neural retina contain?

A

ganglionic cell bodies (thicker near the retina’s center than its periphery

33
Q

what does the inner plexiform layer (layer 4) of the neural retina contain?

A

fibers/synapses of ganglionic cells and bipolar neurons

34
Q

what does the inner nuclear layer (layer 5 of the neural retina) consist of?

A

bipolar neurons, which integrate signals from rods/cones

35
Q

what does the outer plexiform layer (layer 6 of the neural retina) contain?

A

fibers/synapses of bipolar neurons and rods and cones

36
Q

what does the outer nuclear layer (layer 7 of the neural retina) consist of?

A

cell bodies of rods and cones

37
Q

what does the outer limiting layer (layer 8 of the neural retina) consist of?

A

it is a line of junctional complexes holding photoreceptors to Muller cells

38
Q

what does the inner segment of rods contain?

A

glycogen, mitochondria, and polyribosomes for the cells biosynthetic activity

39
Q

what is the outer segment of rods made up of?

A

it is modified primary cilium

40
Q

what protein is found within the discs of rods?

A

rhodopson

41
Q

what visual pigment do cones contain?

A

iodopsin

42
Q

what is the fovea centralis?

A

it is the area where visual acuity is the sharpest (highest concentration of cones)

43
Q

what is the macula lutea?

A

it surrounds the fovea and protects cones

44
Q

where is the optic disc located?

A

at the head of the optic nerve

45
Q

when does the optic nerve become myelinated?

A

as it passes through the sclera

46
Q

how are visual system lesions described?

A

in terms of their visual field deficits NOT RETINAL FIELDS

47
Q

the left half of the visual field forms an image where?

A

upon the nasal (right) half of the left retina and the temporal (right) half of the right retina

48
Q

the right half of the visual field forms an image where?

A

upon the nasal (left) half of the right retina and the temporal (left) half of the left retina

49
Q

what makes up the optic tract?

A

fibers from the temporal retina (ipsilateral eye) + fibers from nasal retina (contralateral eye)

50
Q

what is responsible for the depth perception?

A

the decussation of CN II

51
Q

where does the optic tract terminate?

A

in the lateral geniculate nucleus (LGN) of the thalamus

52
Q

as axons exit the LGN what do they give rise to?

A

optic radiations, axons that are going to relay the visual information back to the primary visual cortex

53
Q

ganglionic cell axons that arise in the temporal retina remain what? and terminate where?

A

they remain uncrossed and terminate in the ipsilateral LGN

54
Q

axons that arise in the nasal retina do what and terminate where?

A

they cross and terminate in the contralateral LGN

55
Q

where does the optic radiation relay its information to?

A

the primary visual cortex

56
Q

where is the primary visual cortex located?

A

on the upper and lower banks of the calcarine sulcus

57
Q

as fibers leave the LGN, fibers representing the inferior visual field terminate where?

A

superior to the calcarine sulcus

58
Q

as fibers leave the LGN, fibers representing the superior visual field do what and terminate where?

A

they sweep through the temporal loop (meyer’s loop) and terminate inferior to the calcarine sulcus

59
Q

what is the superior colliculus important for?

A

directing eye movements

60
Q

what is the pretectal area important for?

A

important in pupillary light reflex

61
Q

what is hemianopia?

A

blindness in one half of the visual field

62
Q

what is quadrantanopia?

A

blindness of a quadrant of the visual field

63
Q

what is homonymous visual field?

A

conditions in visual field losses are similar in both eyes

64
Q

what is heteronymous visual field?

A

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

65
Q

what is macular sparing?

A

visual field loss that preserves vision in the center of the visual field

66
Q

how are lesions in the optic tracts and optic radiations described?

A

congruous or incongruous

67
Q

what does it mean when a deficit is congruous?

A

when the visual field loss of one eye can be superimposed on that of the other eye

68
Q

when does a lesion become more congruous?

A

the closer a lesion is to the visual cortex

69
Q

when does a lesion become more incongruous?

A

the more anterior a lesion is in the optic tract or radiations

70
Q

damage anterior to the chiasm affects what?

A

only the ipsilateral eye

71
Q

damage to the chiasm causes what?

A

heteronymous deficits

72
Q

damage behind the chiasm causes what?

A

homonymous deficits

73
Q

what is associative visual agnosia?

A

infarction of the left occipital lobe and posterior corpus callosum

74
Q

what is associative visual agnosia typically due to?

A

PCA damage

75
Q

associative visual agnosia is a disconnection between what?

A

the language area from the visual association cortex

76
Q

what is the classical presentation of associative visual agnosia?

A

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

Human basic neuroscience (68 decks)

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