Visual Pathways Flashcards
Main Visual pathway:
GCs>optic nerve>chiasm>LGN>optic radiations>visual cortex
intrinsically photosensitive ganglion cells contain?
melanopsin
2 targets of melanopsin?
- suprachiasmatic nucleus: circadian
2. pretectal n.: midbrain: pupil response
M ganglions detect? what %?
motion: 10%
P ganglions detect?
colour/visual acuity: 80%
target of most GCs?
lateral geniculate nucleus in the thalamus
what happens in superior colliculus?
eye movements
what happens in suprachiasmatic n.?
circadian rhythm
what happens in pretectum midbrain?
pupil responses
what crosses at optic chiasm?
nasal fibres of optic nerve which sense the temporal fields
right visual hemisphere viewed by?
left cortex
left visual hemisphere viewed by?
right cortex
what usually causes problems in the optic chiasm?
pituitary or internal carotid issues
what does the medial geniculate nucleus receive?
hearing signals
how many layers of LGN? divided into which two?
Magnocellular: 1,2 (darker, bigger)
Parvocellular: 3,4,5,6
Which layers in the LGN receive from which eye?
Right:2,3,5
Left:1,4,6
what happens to signal after LGN ?
project as optic radiation to cortex via massive white matter tracts
primary visual cortex is where?
- area 17
2. occipital lobe around calcarine fissure
centre of the visual field is where in the lobe?
most occipital part of the visual cortex
unilateral vision loss lesion is most likely?
before the optic chiasm
bitemporal vision loss lesion is most likely?
optic chiasm
bilateral field loss, lesions is most likely?
after the chiasm
when do you get macular sparing?
unique feature of vascular problem in the visual cortex
how many intrinsically photosensitive ganglion cells per retina?
~5000
intrinsically photosensitive ganglion cells contain what?
melanopsin: like in invertebrates
what happens when melanopsin is hit with light?
depolarizes intrinsically photosensitive ganglion cells
what non vision info do intrinsically photosensitive ganglion cells transmit? 5 things:
- circadian rhythm (hypothalamus)
- sleep regulation
- pupil responses
- general light levels
- light allodynia
photophobia during migraine comes how?
pain signals from dura via trigeminal end up at posterio nucleus of thalamus and intrinsically photosensitive ganglion cells also project there
blind people who have retinas get photophobia?
yes
Pupil response pathway
optic nerve>pretectal nucleus>edinger-westphal>CNIII>sphincter pupillae
where do intrinsically photosensitive ganglion cells with melanopsin project to in the pupil repsonse?
optical pretectal nucleus
where is suprachiasmatic nucleus?
hypothalamus, and affected by intrinsically photosensitive ganglion cells
