Visual System Flashcards
what is the superior colliculus a part of? what is it importnat for?
part of the tectum
-important for orienting eyes and head to not only visual stimuli but also auditory and somatosensory stimuli
where is the accessory optic nuclei?
in the midbrain tegmentum
what central projections of RGCs (retinal ganglion cells) in the optic nerve are in the midbran, hypothalamus, and thalamus
midbrain: pretectal olivary nucleus, superior colliculus (tectum), accessory optic nuclei
hypothalamus: suprachaismitc nucleus
thalamus; lateral geniculate nucleus
which fibers cross and which stay straight
the nasal retinal fibers crossed to the opposite brain
temporal fibers continue straight
the chiasm carries _____ retinal fibers from each eye, representing the _____ field of each eye
chiasm carries nasal retinal fibers form each eye, thereby representing the temporal field of each eye
the tract carries ____ fibers from the _____ retina, and the crossed _____ fibers from the contralateral retina
the tract carries the temporal fibers from the ipsi retina (ipsi nasal field) and the crossed nasal fibers from the contralateral retina (contra temp field)
what are the 6 layers of the LGN
inner 2 layers called magnocellular layer
outer 4 layers are parvocellular
1, 4, 6 get info from contralateral retina (nasal)
2, 3, 5 get info from ipsi (temporal retina)
what is meyer’s loop
some raidations travel inf in the temporal lobe
-these inf radiations are carrying the same field info that was carried int he inf retina which is for the sup field
what is the rule of L’s (wehre do the lower retina fibers go)
lower retinal fibers, to the lateral LGN, into Meyer’s Loop, to synapse on the Lingual gyrus
where does inf field info go
superior retina
superior radiations (parietal lobe)
superior bank of occipital cortex (cuneus)
what separates the nasal from temporal retina
`the fovea
where do distal arcuates come from
where do proximal arcutes come from
distal: come from peripheral RGCs
proximal: RGCs closwer to optic disc
what kind of fibers are papillomacularbundles and where do they insert
nasal retinal fibers inserting into the temporal neuro-retinal rim
-go from the fovea (central) to ONH
what kind of retinal fibers are arcuates and wehre do they insert
temporal retinal fibers that arched over the papillomacular bundle to insert into the superior-temporal and inf-temp neuro retinal rim
-some come from peripheral retina; other start out more centrally
where do nasal fibers come from and where do they insert
nasal retinal fibers that insert into the nasal neuro retinal rim
where do the distal arcuates travel
wehre do the proximal arcuates travel
distal: travel at the bottom of the heap (closwer to RGC layer)
proximal: travel more superficially, on top of distal fibers (closwer to vitreous)
what position in the optic disc to distal arcuates occupy? proximal?
distal: occupy a more peripheral position in the optic disc (near disk margin)
proximal: occupy a more central position in the optic disc (nearer the cup)
although the papillomacular bundle starts out in the temporal neuro-retinal rim, they move to occupy a …in the optic nerve
central location in the optic nerve (closer to the chiasm)
a lesion in the posterior chiasm may cause a …
bitemporal hemianopia, denser below
bc the superior-nasal fibers cross in this portion of the chiasm
what happens in the anterior chiasmal syndrome
causes a junctionalscotoma
- centrol loss (NFB defect) in one eye and superior-temopral loss in the opposite eye
- bitemporal hemianopia (due to crossing nasal fibers) is denser sup earlier on the course of the dieases
where does the papillomacular bundle travel in the chiasm and where does it cross in the chiasm
travels inf in the chiasm and then crosses in the most posterior part of the chiasm
what kind of disease can affect temporal fibers
aneurysm of the ICA which can push on these temporal fibers to cuase a nasal vf defect one eye
what fibers are in the anteriro chiasm?
post chiasm?
what fibers are uncrossed?
ant: inf-nasal fibers (sup-temp field)
post: sup-nasal fibers (inf-temporal field)
- nasal macular fibers (papillomacular bundle)
uncrossed: temporal fibers (arcuates, temporal macular fibers)
what occurs in an ant chiasmal syndrome?
classical chiasmal syndrome?
post chiasmal syndrome?
ant: juctional scotoma
classic: bitemporal field loss
post: central bitemporal
- bitemporal denser below
- incongruous homonymous hemianopia (tract)
superior fibers are superior then move ____
inf fibers move _____
macular fibers are central and move ____
sup move medial
inf move lateral
macular fibers are central then move sup
where do the superior retinal quadrants synapse in? what kind of fibers
medial LGN
uncrossed ST fibers
crossed SN fibers
wehre do the inf retinal quadrants synapse in
what kind of fibers
lateral LGN
uncrossed IT fibers
crossed IN fibers
where do the macular fibers synapse in
what kind of fibers
intermediate LGN
- sup macular fibers go to the medial aspect of the int LGN
- inf macular fibers go to the lateral aspect of the int LGN
the medial LGN contain fibers destined to _____ to the parietal lobe via the ____ radiations.
-represent ______ inf field info
the medial LGN contain fibers destined to head up to the pareital lobe via the sup radiations
-these head to the sup visual cortex and represent contralateral inf field info
the lateral LGN contain fibers destined to _____ to the temporal lobe via the _____ radiations
-these head to the _____ visual cortex and represent contralateral ______ sup field info
the lateral LGN contain fibers destined to head down to the temporal lobe via the inf radiations
-these head to the inf visual cortex and represent contralateral sup field info
a right LGN lesion will cuase a _______
left homonymous hemianopia
optic radiations that go up DORSALLY to the parietal lobe carry info representing the _____ field
inf field
and sup retinal quad
optic radiations that go down VENTRALLY to the temporal lobe represent info from the _____ field
sup field
and inf retinal quadrants
what fissure separates the sup and inf visual cortex
calcarine fissure
what tip is the most posterior part wehre the macular/central vision is represented
occipital tip
what contain the axons of RGCs
retinal nerve fiber layer
optic nerve
optic chiasm
tract
what are the 4 portions of the optic nerve
intraocular (ONH)
intraorbital
intracanalicular
intracranial
what is the longest part of the optic nerve
intraorbital portion
what are the lengths of the papilla, intraorbital, intraosseous, and intracranial
ONH aka papilla: 1mm
intraorbital: 30mm
intraosseous: 6mm
intracranial 10mm
what are the 3 zones of the optic nerve head (aka intraocular optic nerve and papilla)
- prelaminar (ant)
- laminar
- retrolaminar (post )
what are lamina cribosa
holes through which all RGC axons pass to exit the eye –(200-300 holes) through which all optic nerve axons pass
what do axons of retinal ganglion cells become
optic nerve, chiasm, and tract
where does the central retinal artery pierce the optic nerve sheath
10-12mm behind the globe and runs ant in the central aspect of the optic nerve to emerge in the center of the optic disc
which bone is the intracanalicular portion in?
sphenoid, lesser wings
in intraorbitla part goes from behind the ____ to the _____
ONH to the optic foramen
the intracranial portion varies in length, which will afftect the position of what
of the optic chiasm over pituitary gland
what ist he optic chaism superior to? how many mm
10mm above the pituitary gland
-which sits inside the sphenoid bone-the sella turcica
the chiasm lies in the middle of the….
suprasella cistern
-CSF filled subarachnoid suprasellar cistern
the pituitary gland is inf to the chiasm, so pituitary stalk to ______ to the optic chiasm
posterior
in a craniopharyngiomas (usually at the junctin of the infundibulum and the pituitary gland) the turmos can compress the post optic chiasm, what compression can you get and what happens
you get a compression of the crossing sup nasal fibers which mediate inf temporal vision in each eye
-bitemporal hemianopia denser inferiorly
the optic recess is one of the pointy parts ot he 3rd ventricle and is _____ nad ____ to the optic chiasm
right above and post to the optic chiasm
how is the chiasm located in relation to they hypothalamus
chiasm is in front of and inf to the hypothalamus
what ist he anterior and post bony boundary of the sella turcica
ant: tuberculum
post: dorsum
what is a prefixed, normal, and postfixed chiasm?
normal: above the diaphrgma sellae
prefixed: intracranial optic nerves are short, the optic chiasm is positioned ant and sits over the tuberculum sellae
postfixed: intracranial nerves are long, the chiasm is positioned post to the dorsum sellae
if you have a postfixed chiasm where the chiasm is “fixed” to the dorsum sellae, then if the pittuitary below were to expand larger than 10mm, what would you be more likely to compress? the ant, middle, or post chiasm?
ant chiasmal syndrom/junctional scotoma
what can occur from a retrochiasmal lesion (meaning a lesion occuring anywehre starting behind the chiasm all the way to the visual cortex)
homonymous hemianopia
why can you not get an RAPD from a lesion at the LGN, radiations, or visual cortex?
pupil light reflex pathway bypasses the LGN
once the optic radiations leave the LGN, they traverse the most ______ aspect of the _______ . after this they course post to the visual cortex
most posterior aspect of the post limb of the internal capsule
why is there meyer’s loop
the ventral horizontal bundle (inf optic rad) have to skirt around the inf horn of the lateral ventricle, which is in the temporal lobe
If you have a lesion to the right occipital lobe above the calcarine fissure, what kind of field defect would you expect?
left inferior HH
in the occipital lobe, if there is a lesion in the posterior region what thing will you get
highly congruous homonymous hemianopia
- often respects both the vertical and horiz
- a true qandrantonopia
if there is a lesion in the ant occipital lobe what will you get
monocular temporal crescent
what can be spared when there is a lesion in the occipital lobe
macula or temporal crescent may be spared
-macula represented at TIP (most post)
