ANAT visual tracts Flashcards
what forms the visual pathway
axons of ganglion cells and axons of higher order cells on which they synapse
what is a visual field
area a person is able to see when both eyes are fixed in one position
what is the optic disc
region where retinal axons leave the eye as the optic nerve
no photoreceptors present here, creates our blindspot
fibers from where run in the optic tract
fibers from ipsilateral temporal retina
fibers from contralateral nasal retina
where does the optic tract terminate
lateral geniculate nucleus (LGN)
what forms the ventral base of the LGN
incoming optic tract (reticulogeniculate) fibers
what forms the dorsal and lateral borders of the LGN
outgoing optic radiations
magnocellular layers
layers 1 and 2 (ventral) of LGN
ganglion cell inputs relaying from rods
sensitive to moving stimuli
parvocellular layers
layers 3-6 (dorsal) of LGN
ganglion cell inputs relaying from cones
responsive to stationary stimuli, high-acuity color vision
pathway of temporal retina
remain ipsilateral and terminate in layers 2,3, and 5 of LGN
pathway of nasal retina
cross and terminate in layers 1,4, and 6 of contralateral LGN
fibers from the lower quadrant of the contralateral hemifields:
originate
where do they go
originate from dorsomedial portion of LGN
arch caudally to pass through retrolenticular limb of IC
target superior bank of calcarine sulcus, on the cuneus
fibers from the upper quadrant of the contralateral hemifields:
originate
where do they go
originate from ventrolateral portion of LGN
arch rostrally, passing into white matter of temporal
lobe and looping, forming meyer loop
target inferior bank of calcarine sulcus, on lingual gyrus
fibers from macula and fovea
originate
where do they go
originate from central regions of LGN
pass to caudal portions of visual cortex
what composes the visual association cortex (extrastriate cortex)
areas 18, 19, and related parts of the temporal and parietal lobes
other visual cortical areas and f(x)
superior colliculus: directing eye movements
pretectal area: pupillary light reflex
congruous visual field deficit
visual field loss of one eye can be superimposed on that of the other eye (symmetrical)
the closer a lesion is to the visual cortex, the more congruous it is likely to be
overarching concept of visual field deficits
damage anterior to chiasm affects only ipsilateral eye
damage at chiasm causes heteronymous deficits
damage behind chiasm causes homonymous deficits
associative visual agnosia
infarction of the left occipital lobe and posterior corpus callosum
pt cannot name or describe an object in the visual field, but he can recognize and demonstrate its use
