Non-Visual RGCs (F)

Question 1

What are the advantages of having the photoreceptors in the outer retina and having a “backward” design?

Answer 1

1. photoreceptors placed in contact with the RPE (chromophore regeneration)
2. in contact with the choroid (blood supply)

Question 2

Which retinal circuits are best stimulated by light objects on dark background?

Answer 2

ON circuits

Question 3

Which retinal circuits are best stimulated by dark objects on light background?

Answer 3

OFF circuits

Question 4

What is the purpose of the lateral inhibition mediated first by horizontal cells and later amacrine and inhibitory cells in LGN?

Answer 4

sharpen edges and borders in our perception of images (enhance contrast)

Question 5

What are the other major RGC projections from the retina, other than to the LGN?

Answer 5

1. hypothalamus
2. pretectum
3. superior colliuculs

Question 6

What is the function of the pulvinar?

Answer 6

involved in visual attention

Question 7

What is the function of the superior colliculus?

Answer 7

saccade generation; reflex head and neck movements to stimuli

Question 8

What is the function of the lateral habenula?

Answer 8

emotion, pain processing, learning

Question 9

What is the function of the ventrolateral pre-optic nucleus in the hypothalamus?

Answer 9

sleep regulation

Question 10

What is the function of the suprachiasmatic nucleus in the hypothalamus?

Answer 10

synchronization of circadian rhythms

Question 11

What is the function of the pretectum (olivary pretectal nucleus)?

Answer 11

pupillary light reflex

Question 12

What is the pathway from the pretectum to pupil constriction?

Answer 12

pretectum project bilaterally to Edinger-Westphal nuclei then synapse in ciliary ganglion then synapse on constrictor muscle of iris

Question 13

What is the irradiance information from the eye used for?

Answer 13

1. regulate pupil size

2. body’s circadian rhythms

Question 14

What is the generalized rule for the time it takes to resynchronize an internal clock after changing time zones?

Answer 14

about 1 day per time zone crossed

Question 15

Does melatonin go up or down at night? 1. Body temp? 2

Answer 15

1. up

2. down

Question 16

Why are our internal cues often masked or ignored in everyday life?

Answer 16

artificial timing cues

Question 17

What is the internal “free running” circadian rhythm of humans?

Answer 17

24.5 hrs

Question 18

What happens to the circadian cycle when the eyes are enucleated?

Answer 18

it no longer exists for the patient

Question 19

Are rods and cones necessary for irradiance detection?

Answer 19

no

Question 20

What are the non-rod or cone cells that are photosensitive in the retina?

Answer 20

intrinsically photosensitive RGCs (ipRGCs)

Question 21

What photopigment is expressed in ipRGCs? 1. Where do these cells project to in the brain? 2. How many of these are found in the human retina? 3

Answer 21

1. melanopsin
2. suprachiasmatic nucleus (SCN) and olivary pretectal nucleus (OPN, pretectum)
3. 3,000

Question 22

What is the peak spectral sensitivity of ipRGCs? 1. What is their relative sensitivity compared to rods and cones? 2

Answer 22

1. 480nm

2. not very sensitive

Question 23

What is the relative temporal resolution of ipRGCs?

Answer 23

much lower than conventional RGCs (flicker must be very slow (less than 1 Hz))

Question 24

What cell types in the retina can mediate pupil reflexes?

Answer 24

1. rods/cones

2. ipRGCs