The targets of ganglion cells (visual pathways) Flashcards Preview

MD2- Neuroscience Block > The targets of ganglion cells (visual pathways) > Flashcards

Flashcards in The targets of ganglion cells (visual pathways) Deck (29):
1

bitemporal hemianopia?

loss of vision on the temporal/lateral sides of the visual field bilaterally

2

what do M ganglion cells do?

provide information about motion.
larger cells than P ganglion cells, and have longer processes.

3

what do P ganglion cells do?

sense color vision, provide visual acuity. more numerous and smaller than M cells.

4

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.

5

which thalamic nuclei is the main target for ganglion cells in the visual pathway?

LGN (LATERAL GENICULATE NUCLEUS)

6

WHERE DO THE RIGHT AND LEFT OPTIC NERVES COMBINE?

OPTIC CHIASM

7

where is optic chiasm located?

at base of brain, anterior to pituitary gland.

8

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.

9

right hemisphere picks up visual information from?

nasal field of left eye and lateral field of right eye.

10

lesion/tumor in pituitary would most likely cause what visual disturbance?

bitemporal hemianopia

11

where is the LGN located?

bilaterally on the posterior surface of thalamus.

12

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.

13

optic radiations?

axons of neurons that have radiated down from the layers of the LGN towards the occipital lobe.

14

where do LGN neurons project to? (where on the occipital lobe)

primary visual cortex. (broadmann's area 17).

15

retinotopic organization?

neighboring cells within the retina project to neighboring cells within the LGN and primary visual cortex.

16

what divides the primary visual cortex in half?

calcarine fissure

17

lesion to right optic nerve will cause what visual problem?

complete loss of right eye visual field.

18

lesion impacting optic chiasm will cause what visual disturbance>

bitemporal hemianopia

19

lesion affecting the right optic tract will cause what visual disturbance?

loss of left visual field on both eyes.

20

TRUE/FALSE. As you go along the calcarine fissure anteriorly you encode information from more peripheral parts of the retina.

TRUE>

21

if a visual defect occurs on the same side in both eyes, where is the lesion in relation to the optic chiasm?

post-chiasm

22

what quality is intrinsic to photosensitive ganglion cells (IPGC's)

contain the photosensitive pigment melanopsin.

23

what reaction does light activation of the melanopsin pigment cause?

depolarization of IPGC's

24

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.

25

which muscles is the pupil's response to light dependant on?

sphincter pupillae (constriction) and dilator pupillae (dilation)

26

T/F: Melanopsin Ganglion cells project to the LGN of the thalamus.

False! They project to the optical pretectal nucleus (OPN) of the midbrain. then they crossover and reach the contralateral edinger-westfal nucleus before sending PS nerve fibres back to iris.

27

which part of hypothalamus drives circadian rhythm?

(SCN) suprachiasmatic nucleus of hypothalamus.

28

how do IPGC's influence circadian rhythm?

transmit information re: environmental light levels to the suprachiasmatic nucleus of the hypothalamus.

29

how is photophobia caused by IPGC's

IPGC's project to posterior thalamic nucleus.
Pain pathway: dura-->trigeminal nerve-->brain stem
-->thalamus.
Pain signal is carried to posterior nucleus of thalamus & this is also where IPGC's project.

Thus light makes the migraine pain worse by adding pain from environmental light to the equation.