Geniculocortical Pathway

Question 1

what are the major bundles of the nerve fiber layers?

Answer 1

arcuate fibers, papillomacular fibers, horizontal raphe, and radial bundles

Question 2

arcuate fibers

Answer 2

From temporal retina superior and inferior to the macula, converge near the optic disc

Question 3

papillomacular fibers

Answer 3

from macular region to optic disc

Question 4

horizontal raphe

Answer 4

a horizontal line that divides the retina into two vascular hemispheres and separates the nerve fiber layers in the temporal retina

Question 5

radial bundles

Answer 5

extend from peripheral retina towards the optic disc

Question 6

where does the optic nerve become the optic disc?

Answer 6

as it approaches the lamina cribosa

Question 7

what does the optic disc lack? and what’s the process called to mask it?

Answer 7

it lacks photoreceptors (meaning a blindspot), masked when both eyes are open and by a process called physiological filling in (under monocular conditions)

Question 8

What are the 4 portions of the optic nerve?

Answer 8

intraocular portion, intraorbital portion, intracanalicular portion, and intracranial portion

Question 9

intraocular portion includes

Answer 9

eyeball up to the lamina cribosa

Question 10

intraorbital portion includes

Answer 10

lamina cribosa up to the optic canal

Question 11

intracanalicular portion includes

Answer 11

the optic canal

Question 12

intracranial portion

Answer 12

posterior from the optic canal to the optic chiasm

Question 13

what occurs at the optic chiasm?

Answer 13

a partial decussation of optic nerve fibers, the nasal hemiretina crosses, while the temporal hemiretina stays ipsilateral

Question 14

what is the optic tract?

Answer 14

the posterior portion after the optic chiasm, where the contra nasal hemiretinal and ipsi temporal hemiretina travels through

Carries information for contra visual field

Question 15

What issue does the optic chiasm face?

Answer 15

it’s in a “precarious position”
aka surrounded by a lot of other structures

Question 16

what is the most common type of visual field loss, when the optic chiasm is lesioned?

Answer 16

A bitemporal hemianopia

Question 17

what would a lesion in the optic tract or caudal to this point cause?

Answer 17

a visual field loss in in the same hemifield of both eyes, also always will be contralateral to lesion side

Question 18

which layers of the LGN receive input from the contralateral eye?

Answer 18

Layers 1, 4, and 6

Question 19

which layers of the LGN receive input from the ipsilateral eye?

Answer 19

Layers 2, 3, and 5

Question 20

alignment of monocular inputs is called what?

Answer 20

A line of projection

Question 21

magnocellular layers

Answer 21

layers 1 and 2, large cellular layers

low spatial frequency, better for large moving things and dimmer lighting

Question 22

parvocellular layers

Answer 22

layers 3-6, contain small cell bodies

high spatial frequency, better for smaller, detailed things

Question 23

what is cortical magnification?

Answer 23

central vision at the LGN becomes magnified

Question 24

what does optic radiations represent?

Answer 24

represent the geniculostriate projection to reach primary visual cortex

Question 25

superior vision vs inferior vision route

Answer 25

1. superior vision: lower retina, lateral LGN, Meyer’s loop in the temporal lobe, to lingual gyrus
2. inferior vision: upper retina, medial LGN, straight course through parietal lobe, cuneus gyrus

Question 26

Rostral vs caudal primary cortex

Answer 26

rostral: peripheral retina

caudal: central retina (foveal=caudal pole)