Visual Tracts

Question 1

What forms the visual pathway?

Answer 1

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

Question 2

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

Answer 2

retinotopic

Question 3

what are the three layers of the eye?

Answer 3

fibrous layer, vascular layer, retina

Question 4

what does the fibrous layer of the eye consist of?

Answer 4

the sclera and the cornea

Question 5

what does the vascular layer of the eye consist of?

Answer 5

choroid, ciliary body, and the iris

Question 6

what is the role of the sclera?

Answer 6

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

Question 7

what type of tissue makes up the sclera?

Answer 7

dense regular CT with flat bundles of type I collagen

Question 8

what are the five distinct layers of the cornea?

Answer 8

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

Question 9

what type of tissue makes up the corneal epithelium?

Answer 9

nonkaratinized stratified squamous epithelium

Question 10

what separates the corneal epithelium from the stroma?

Answer 10

the anterior limiting membrane (Bowman membrane)

Question 11

what makes up the stroma?

Answer 11

keratocytes

Question 12

what separates the stroma from the inner endothelium?

Answer 12

the posterior limiting membrane (Descemet’s membrane)

Question 13

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

Answer 13

limbus

Question 14

what does the limbus denote?

Answer 14

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

Question 15

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

Answer 15

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

Question 16

what is the middle layer of the eye?

Answer 16

the vascular layer

Question 17

what does the choroid consist of?

Answer 17

loose, well-vascularized connective tissue and melanocytes

Question 18

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

Answer 18

it prevents light from entering the eye except via the pupil

Question 19

what is the Bruch’s membrane?

Answer 19

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

Question 20

what is the innermost layer of the eye?

Answer 20

the retina

Question 21

what are the two layers of the retina?

Answer 21

1. outer pigmented layer and 2. inner neural layer

Question 22

what does the retina develop from?

Answer 22

the optic cup

Question 23

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

Answer 23

simple cuboidal epithelium

Question 24

what makes up the inner neural layer of the retina?

Answer 24

it is stratified with various neurons and photoreceptors

Question 25

the neural component of the retina extends to where?

Answer 25

anteriorly to the ora serrata

Question 26

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

Answer 26

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

Question 27

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

Answer 27

the pigmented epithelium

Question 28

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

Answer 28

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

Question 29

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

Answer 29

it is a basement membrane covered by processes of Muller cells

Question 30

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

Answer 30

ganglionic cell axons

Question 31

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

Answer 31

they converge at the optic disc and they form CN II

Question 32

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

Answer 32

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

Question 33

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

Answer 33

fibers/synapses of ganglionic cells and bipolar neurons

Question 34

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

Answer 34

bipolar neurons, which integrate signals from rods/cones

Question 35

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

Answer 35

fibers/synapses of bipolar neurons and rods and cones

Question 36

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

Answer 36

cell bodies of rods and cones

Question 37

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

Answer 37

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

Question 38

what does the inner segment of rods contain?

Answer 38

glycogen, mitochondria, and polyribosomes for the cells biosynthetic activity

Question 39

what is the outer segment of rods made up of?

Answer 39

it is modified primary cilium

Question 40

what protein is found within the discs of rods?

Answer 40

rhodopson

Question 41

what visual pigment do cones contain?

Answer 41

iodopsin

Question 42

what is the fovea centralis?

Answer 42

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

Question 43

what is the macula lutea?

Answer 43

it surrounds the fovea and protects cones

Question 44

where is the optic disc located?

Answer 44

at the head of the optic nerve

Question 45

when does the optic nerve become myelinated?

Answer 45

as it passes through the sclera

Question 46

how are visual system lesions described?

Answer 46

in terms of their visual field deficits NOT RETINAL FIELDS

Question 47

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

Answer 47

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

Question 48

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

Answer 48

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

Question 49

what makes up the optic tract?

Answer 49

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

Question 50

what is responsible for the depth perception?

Answer 50

the decussation of CN II

Question 51

where does the optic tract terminate?

Answer 51

in the lateral geniculate nucleus (LGN) of the thalamus

Question 52

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

Answer 52

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

Question 53

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

Answer 53

they remain uncrossed and terminate in the ipsilateral LGN

Question 54

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

Answer 54

they cross and terminate in the contralateral LGN

Question 55

where does the optic radiation relay its information to?

Answer 55

the primary visual cortex

Question 56

where is the primary visual cortex located?

Answer 56

on the upper and lower banks of the calcarine sulcus

Question 57

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

Answer 57

superior to the calcarine sulcus

Question 58

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

Answer 58

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

Question 59

what is the superior colliculus important for?

Answer 59

directing eye movements

Question 60

what is the pretectal area important for?

Answer 60

important in pupillary light reflex

Question 61

what is hemianopia?

Answer 61

blindness in one half of the visual field

Question 62

what is quadrantanopia?

Answer 62

blindness of a quadrant of the visual field

Question 63

what is homonymous visual field?

Answer 63

conditions in visual field losses are similar in both eyes

Question 64

what is heteronymous visual field?

Answer 64

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

Question 65

what is macular sparing?

Answer 65

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

Question 66

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

Answer 66

congruous or incongruous

Question 67

what does it mean when a deficit is congruous?

Answer 67

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

Question 68

when does a lesion become more congruous?

Answer 68

the closer a lesion is to the visual cortex

Question 69

when does a lesion become more incongruous?

Answer 69

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

Question 70

damage anterior to the chiasm affects what?

Answer 70

only the ipsilateral eye

Question 71

damage to the chiasm causes what?

Answer 71

heteronymous deficits

Question 72

damage behind the chiasm causes what?

Answer 72

homonymous deficits

Question 73

what is associative visual agnosia?

Answer 73

infarction of the left occipital lobe and posterior corpus callosum

Question 74

what is associative visual agnosia typically due to?

Answer 74

PCA damage

Question 75

associative visual agnosia is a disconnection between what?

Answer 75

the language area from the visual association cortex

Question 76

what is the classical presentation of associative visual agnosia?

Answer 76

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