The targets of ganglion cells (visual pathways)

Question 1

bitemporal hemianopia?

Answer 1

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

Question 2

what do M ganglion cells do?

Answer 2

provide information about motion.

larger cells than P ganglion cells, and have longer processes.

Question 3

what do P ganglion cells do?

Answer 3

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

Question 4

where do M and P ganglion cells fit within the context of ON and OFF ganglion cells?

Answer 4

ON and OFF overlap with these cells. ie OFF M cells and ON M cells. also OFF P cells and ON P cells.

Question 5

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

Answer 5

LGN (LATERAL GENICULATE NUCLEUS)

Question 6

WHERE DO THE RIGHT AND LEFT OPTIC NERVES COMBINE?

Answer 6

OPTIC CHIASM

Question 7

where is optic chiasm located?

Answer 7

at base of brain, anterior to pituitary gland.

Question 8

left and right visual field project onto which side of eyeball?

Answer 8

left visual hemifield projects onto right side of eye, right visual hemifield projects onto left side of eye.

Question 9

right hemisphere picks up visual information from?

Answer 9

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

Question 10

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

Answer 10

bitemporal hemianopia

Question 11

where is the LGN located?

Answer 11

bilaterally on the posterior surface of thalamus.

Question 12

how many layers within the LGN? how are they split up?

Answer 12

6 layers. 2 Magno layers, 4 parvo layers. Info from each eye is segregated in each layer, no mixing.

Question 13

optic radiations?

Answer 13

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

Question 14

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

Answer 14

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

Question 15

retinotopic organization?

Answer 15

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

Question 16

what divides the primary visual cortex in half?

Answer 16

calcarine fissure

Question 17

lesion to right optic nerve will cause what visual problem?

Answer 17

complete loss of right eye visual field.

Question 18

lesion impacting optic chiasm will cause what visual disturbance>

Answer 18

bitemporal hemianopia

Question 19

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

Answer 19

loss of left visual field on both eyes.

Question 20

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

Answer 20

TRUE>

Question 21

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

Answer 21

post-chiasm

Question 22

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

Answer 22

contain the photosensitive pigment melanopsin.

Question 23

what reaction does light activation of the melanopsin pigment cause?

Answer 23

depolarization of IPGC’s

Question 24

what are some functions of intrinsic photosensitive ganglion cells? (IPGC’s)

Answer 24

circadian rhythm
sleep regulation
pupil responses
light allodynia
general information about light levels in environment.

Question 25

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

Answer 25

sphincter pupillae (constriction) and dilator pupillae (dilation)

Question 26

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

Answer 26

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.

Question 27

which part of hypothalamus drives circadian rhythm?

Answer 27

(SCN) suprachiasmatic nucleus of hypothalamus.

Question 28

how do IPGC’s influence circadian rhythm?

Answer 28

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

Question 29

how is photophobia caused by IPGC’s

Answer 29

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.