W21-L5: Visual pathways Flashcards
What are the types of ganglion cells?
M cells that see motion, project to magnocellular and P cells that are 80% of ganglion cells that detect colour vision and acuity
Which fibres decussate at the optic chiasm?
Nasal fibres of each retina
What is the main target of ganglion cells?
LGN of the thalamus
What are the layers of the LGN?
Magnocellular layers are 1 and 2, parvocellular are layers 3-6
How are the eyes segregated in the LGN?
contralateral Nasal area= 2,3,5
Ipsilateral Temporal area= 1,4,6
Where do LGN neurones project to?
Primary visual cortex, area 17, which is around the calcarine fissure
Where is central vision represented on the calcarine fissure?
Most posterior aspect
What deficit does an optic nerve tract lesion cause?
unilateral eye visual field loss
If there is a deficit in opposite sides of the visual field where is the lesion?
The optic chiasm, eg bitemporal (tunnel vision)
If there is the deficit in the same side of both visual fields where is the lesion?
Its posterior to the optic chiasm
What are Intrinsically photosensitive Ganglion Cells?
A small population of GCs contain a visual pigment called melanopsin
What is the function of Intrinsically photosensitive Ganglion Cells?
- Circadian rhythm
- Sleep regulation
- Pupil responses
- General information about light levels
- Light Allodynia
Where do Intrinsically photosensitive Ganglion Cells project to?
Supra chiasmatic nucleus of the hypothalamus
T/F Blind people with intact retina those who get migraines still have photophobia, without intact retina/optic nerve there was no photophobia
True
Where is the pain signal in migraine photophobia carried to?
Posterior nucleus of the thalamus via CN V
