The targets of ganglion cells (visual pathways) Flashcards
bitemporal hemianopia?
loss of vision on the temporal/lateral sides of the visual field bilaterally
what do M ganglion cells do?
provide information about motion.
larger cells than P ganglion cells, and have longer processes.
what do P ganglion cells do?
sense color vision, provide visual acuity. more numerous and smaller than M cells.
where do M and P ganglion cells fit within the context of ON and OFF ganglion cells?
ON and OFF overlap with these cells. ie OFF M cells and ON M cells. also OFF P cells and ON P cells.
which thalamic nuclei is the main target for ganglion cells in the visual pathway?
LGN (LATERAL GENICULATE NUCLEUS)
WHERE DO THE RIGHT AND LEFT OPTIC NERVES COMBINE?
OPTIC CHIASM
where is optic chiasm located?
at base of brain, anterior to pituitary gland.
left and right visual field project onto which side of eyeball?
left visual hemifield projects onto right side of eye, right visual hemifield projects onto left side of eye.
right hemisphere picks up visual information from?
nasal field of left eye and lateral field of right eye.
lesion/tumor in pituitary would most likely cause what visual disturbance?
bitemporal hemianopia
where is the LGN located?
bilaterally on the posterior surface of thalamus.
how many layers within the LGN? how are they split up?
6 layers. 2 Magno layers, 4 parvo layers. Info from each eye is segregated in each layer, no mixing.
optic radiations?
axons of neurons that have radiated down from the layers of the LGN towards the occipital lobe.
where do LGN neurons project to? (where on the occipital lobe)
primary visual cortex. (broadmann’s area 17).
retinotopic organization?
neighboring cells within the retina project to neighboring cells within the LGN and primary visual cortex.
what divides the primary visual cortex in half?
calcarine fissure
lesion to right optic nerve will cause what visual problem?
complete loss of right eye visual field.
lesion impacting optic chiasm will cause what visual disturbance>
bitemporal hemianopia
lesion affecting the right optic tract will cause what visual disturbance?
loss of left visual field on both eyes.
TRUE/FALSE. As you go along the calcarine fissure anteriorly you encode information from more peripheral parts of the retina.
TRUE>
if a visual defect occurs on the same side in both eyes, where is the lesion in relation to the optic chiasm?
post-chiasm
what quality is intrinsic to photosensitive ganglion cells (IPGC’s)
contain the photosensitive pigment melanopsin.
what reaction does light activation of the melanopsin pigment cause?
depolarization of IPGC’s
what are some functions of intrinsic photosensitive ganglion cells? (IPGC’s)
circadian rhythm sleep regulation pupil responses light allodynia general information about light levels in environment.
