Visual Pathway

overview of visual pathway

retina→ optic nerve→ optic chiasm→ optic tract→ LGN→ optic radiations→ primary visual cortex→ secondary and associate visual cortex

10% of retinal fibers go to this pathway

non-image forming

90% if retinal nerve fibers go to this pathway

image forming

the non-image forming pathway is mediated by a small % of rods and cones as well as

intrinsically photosensitive retinal ganglion cells (IpRGC)

in the non-image forming pathway, what is responsible for the pupillary light reflex?

pretectal olivary nucleus

what is the responsibility of the non-image forming suprachiasmatic nucleus of the hypothalamas

circadian rhythm

what does the pineal gland secrete

melatonin

responsible for photo-entrainment, sleep/wake cycle

suprachiasmatic nucleus of the hypothalamus

the image forming pathway is responsible for what in our vision?

brightness, color, acuity, contrast, motion, spacial and temporal dimensions

in the image forming pathway, what do ipRGC’s contribute to?

color, contrast, patterns

does the pupillary light pathway go to the visual cortex?

NO

what is the orientation of an image on the retina

nasal field is imaged on temporal retina, superior field is imaged on the inferior retina

what are the 4 quadrants of the retina?

superior, inferior, temporal, nasal

do nasal or temporal fibers cross?

nasal

which fibers stay on the same side?

temporal

muller cells forming the ILM are continuous with astrocytes forming the what

internal limiting membrane of elschnig

what is the central meniscus of Kuhnt?

thickened ILM at the center of the optic disc

fibrous tissue extending from the sclera and fuses with bruchs membrane, separates choroid from RGC axons

border tissue of elschnig

astrocytes surrounding the optic canal

border tissue of jacoby

intermediary tissue of kuhnt

extension of the border tissue of jacoby, separates RGC axons from outer retina

separated into about 1000 bundles of axons by astrocytes (fascicles)

retinal nerve fibers

what is septa

connective tissue derived from pia matter

what are nerve fascicles and surrounding astrocytes separated by connective tissues called?

septa

at what part do nerve fibers become myelinated

external part of the lamina cribosa

outermost sheath, tough connective tissue and elastic tissue

dura mater

middle thin collagenous membrane, continuous with intracranial subarachnoid space and contains CSF

arachnoid mater

innermost sheath, loose vascular connective tissue, supplies blood and connective tissue in the septa into the nerve

pia mater

what is GI. M

mantle of astrocytes

GI. C are

oligodendrocytes

what 4 segments are CN2/ optic nerve divide into?

introcular, intraorbital, intracanalicular, intracranial

which segment of the optic nerve is the longest?

intraorbital

which segment of the optic nerve is S shaped, sheaths of SR and MR adhere to sheath of CN and has 3 meningeal sheaths

intraorbital

what segment of the optic nerve is 1.5 to 1.8 mm wide and has nerve fibers with no myelin?

intraocular (prelaminar)

what segment of the optic nerve is 3mm wide and contains nerve fiber, pia mater, and septa

intraocular (laminar)

which segment of the optic nerve is 4 to 5 mm wide, contains nerve fiber, pia, septa, oligiodendrocytes, Arachnoid and Dura

intraorbital (post laminar)

1-2 million retinal nerve fibers make a 90 degree turn at the optic disc and exit as what?

optic nerve/ CN2

What segment of the optic nerve is the shortest

intraocular

the optic chiasm lies within what structure?

circle of willis

the optic chiasm lis below the

hypothalamus

what is located below the optic chiasm?

pituitary gland

what is posterior to the optic chiasm

infundibulum

where do fibers cross

optic chiasm

what % of retinal fibers from each eye will join the contralateral optic tract

50%

which fibers cross more anteriorly

inferior nasal fibers

superior nasal fibers cross more

posteriorly

temporal fibers course through the chiams and remain in the _______ optic tract

ipsilateral

if there is a pituitary tumor on the optic chiasm, what will the VF look like

temporal VF will be impacted

if there is an ICA anuersym on the right side, what VF and eye will be impacted

right nasal VF

in the optic tract, 90% of fibers will synapse where

lateral geniculate nucleus

ipsilateral temporal fibers will synapse with_______ nasal fibers

contralateral

where is the LGN located

dorsolateral aspect of thalamus

where do retinal axons terminate?

LGN

LGN contains visual input from

both eyes

true or false: the LGN is a layered structure- if true, what are the layers

true; magnocellular, parvocellular, koniocellular

many of the fibers leaving the LGN project on to the

visual cortex

How many layers does the magnocellular make up

2 (layers 1 and 2)

what are the magnocellular layers responsible for

motion, contrast, depth

what is found in the magnocellular layer?

large cell bodies

how many layers does the parvocellular layer make up

4 layers (3-6)

what is the parvocellular layer responsible for ?

fine spatial resolution (fine detail), color vision

what is found in the parvocellular layer?

medium sized cell bodies

true or false the koniocellular layer makes up layers 7-10

false, it sits between the layer

the koniolayer is responsible for what

receiving information from retina and superior colliculus, modulates information from different pathways

the six koniocellular layers contain what

small cell bodies

crossed fibers (contralateral eye) projects to which layers of the LGN

1,4,6

uncrossed fibers (ipsilateral eye) project to layers

2,3,5

fibers from ipsilateral (temporal) retina terminate in which layers?

2,3,5

fibers from contralateral (nasal) retina terminate in layers

1,4,6

fibers that originate in neighboring areas of the all layers of LGN terminate in the same place in

striate cortex

has upper and lower division, speads out in a fan shape

optic radiations

what part of the visual pathway carries visual information from both eyes

optic radiations

what side of vision does the right side of the brain give rise to

left