Visual Pathways

Question 1

Main Visual pathway:

Answer 1

GCs>optic nerve>chiasm>LGN>optic radiations>visual cortex

Question 2

intrinsically photosensitive ganglion cells contain?

Answer 2

melanopsin

Question 3

2 targets of melanopsin?

Answer 3

1. suprachiasmatic nucleus: circadian

2. pretectal n.: midbrain: pupil response

Question 4

M ganglions detect? what %?

Answer 4

motion: 10%

Question 5

P ganglions detect?

Answer 5

colour/visual acuity: 80%

Question 6

target of most GCs?

Answer 6

lateral geniculate nucleus in the thalamus

Question 7

what happens in superior colliculus?

Answer 7

eye movements

Question 8

what happens in suprachiasmatic n.?

Answer 8

circadian rhythm

Question 9

what happens in pretectum midbrain?

Answer 9

pupil responses

Question 10

what crosses at optic chiasm?

Answer 10

nasal fibres of optic nerve which sense the temporal fields

Question 11

right visual hemisphere viewed by?

Answer 11

left cortex

Question 12

left visual hemisphere viewed by?

Answer 12

right cortex

Question 13

what usually causes problems in the optic chiasm?

Answer 13

pituitary or internal carotid issues

Question 14

what does the medial geniculate nucleus receive?

Answer 14

hearing signals

Question 15

how many layers of LGN? divided into which two?

Answer 15

Magnocellular: 1,2 (darker, bigger)
Parvocellular: 3,4,5,6

Question 16

Which layers in the LGN receive from which eye?

Answer 16

Right:2,3,5
Left:1,4,6

Question 17

what happens to signal after LGN ?

Answer 17

project as optic radiation to cortex via massive white matter tracts

Question 18

primary visual cortex is where?

Answer 18

1. area 17

2. occipital lobe around calcarine fissure

Question 19

centre of the visual field is where in the lobe?

Answer 19

most occipital part of the visual cortex

Question 20

unilateral vision loss lesion is most likely?

Answer 20

before the optic chiasm

Question 21

bitemporal vision loss lesion is most likely?

Answer 21

optic chiasm

Question 22

bilateral field loss, lesions is most likely?

Answer 22

after the chiasm

Question 23

when do you get macular sparing?

Answer 23

unique feature of vascular problem in the visual cortex

Question 24

how many intrinsically photosensitive ganglion cells per retina?

Answer 24

~5000

Question 25

intrinsically photosensitive ganglion cells contain what?

Answer 25

melanopsin: like in invertebrates

Question 26

what happens when melanopsin is hit with light?

Answer 26

depolarizes intrinsically photosensitive ganglion cells

Question 27

what non vision info do intrinsically photosensitive ganglion cells transmit? 5 things:

Answer 27

1. circadian rhythm (hypothalamus)
2. sleep regulation
3. pupil responses
4. general light levels
5. light allodynia

Question 28

photophobia during migraine comes how?

Answer 28

pain signals from dura via trigeminal end up at posterio nucleus of thalamus and intrinsically photosensitive ganglion cells also project there

Question 29

blind people who have retinas get photophobia?

Answer 29

yes

Question 30

Pupil response pathway

Answer 30

optic nerve>pretectal nucleus>edinger-westphal>CNIII>sphincter pupillae

Question 31

where do intrinsically photosensitive ganglion cells with melanopsin project to in the pupil repsonse?

Answer 31

optical pretectal nucleus

Question 32

where is suprachiasmatic nucleus?

Answer 32

hypothalamus, and affected by intrinsically photosensitive ganglion cells