week 2

Question 1

T/F: cone synaptic endings are slightly above rods in OPL?

Answer 1

FALSE, rods are above cones

Question 2

The synaptic endings in the IPL closer to the INL are for the ____ while those that are farther are for:

Answer 2

closer to INL=dark sensitive bipolar cells

farther=light sensitive bipolar cells

Question 3

what is in the Hanle layer in the retina?

Answer 3

synaptic endings of cones

Question 4

horizontal cells are involved in what process at what retinal layer?

Answer 4

horizontal cells are involved in neg feedback/lateral inhibition of photoreceptor in the OPL

Question 5

amacrine cells are involved in what process at what retinal layer?

Answer 5

amacrine cells are involved in lateral inhibition at the level of the IPL

Question 6

what inserts into a rod’s invaginations?

Answer 6

everything does (unlike cones, where some things insert, some things insert next to them)

Question 7

what inserts into a cone’s synaptic invaginations?

Answer 7

horizontal cells insert into invaginations, and also bipolar cells that are turned on by light
-those turned on by dark insert next to them

Question 8

Describe ERP vs LRP:

Answer 8

ERP = Early Receptor Potential, LRP = Late Receptor Potential
•ERP: electrical change due to photopigment response and it is the quanta absorbed by rhodopsin
•LRP: overall response and it is easy to record since it is so big

Question 9

which has a linear response, ERP or LRP?

Answer 9

ERP has no latency:
This represents the response of the photopigment and has a completely linear response with the increase in luminance since 1 photon will activate 1 rhodopsin molecule all the time

Question 10

app membrane potential of rods and cones at rest:

Answer 10

-20- -30 mV at rest in dark

+Both PRs are activated by dark and inhibited (hyperpolarize) in light

Question 11

In dark, both types of PRs release what NT? (in high amounts?)

Answer 11

glutamate (excitatory)

Question 12

“The receptor membrane potential changes are a logarithmic function of light intensity” how does this impact the way we see?

Answer 12

increases our sensitivity to weak stimuli and makes us less precise in judging brightness

Question 13

the late receptor potential, when plotted as a function of luminance vs amp of response, is a log function. This emphasizes differences bw what kinds of stimuli while minimized differences bw what types of stimuli?

Answer 13

Emphasizes difference between NO STIMULUS and WEAK STIMULUS
Minimizes difference between BRIGHT and BRIGHTER stimulus
We want to detect difference between background and object – our system gets rid of “absolute illumination” information

Question 14

horizontal cells are depol/hyperpol by light?

Answer 14

hyperpolarized (just like PRs)

Question 15

horizontal cells are connected to one another by way of:

Answer 15

gap junctions

Question 16

how many types of bipolar cells?

Answer 16

5: only one of these types stimulated by rods and S-cones

Question 17

for horizontal cells, there is more “cross talk” bw gap junctions in the dark or light?

Answer 17

in the dark

Question 18

The interplexiform cell, a type of amacrine cell, has a true axon that runs back to the OPL to release what NT for what purpose?

Answer 18

release dopamine to loosen the gap junctions between receptors and horizontal cells
**under higher illumination levels

Question 19

Each cone has about ___ invaginations in its large synaptic ending

Answer 19

25

Question 20

horizontal cells are slow or fast acting with short or long latency?

Answer 20

slow acting, long latency

Question 21

Each cone invagination contains:

Answer 21

3 post-synaptic fibers/dendrites inside the invagination:

• 2 x horizontal cells (Off-cell)
• 1 x invaginating bipolar cells (On-cell)

(Other fibers/dendrites lay next to it on flat surface:
2-3x flat bipolar cells (Off-cell))

Question 22

Each rod invagination contains:

Answer 22

Rod axons end in spherules with 1 large invagination containing:
2-5 post-synaptic fibers/dendrites in the invagination
-2 x horizontal cells (Off-cell)
-Many rod bipolar cells (On-cell): specialized for detecting bright objects in a dark surround

Question 23

T/F: rod bipolar cells synapse on ganglion cells?

Answer 23

no; use A11 amacrine cells to cone bipolars to ganglion cells

Question 24

list the 5 major groups of amacrine cells:

Answer 24

1) Neuromodulators
2) Interplexiform Cells
3) Neg feedback/lat inhibition
4) A2 Amacrine cells
5) Linking amacrine cell

Question 25

Neuromodulator amacrine cell function

Answer 25

Alter responsiveness of other amacrine cells to visual stimuli using classic neuromodulator substances (norepinephrine, serotonin, and dopamine) and some unusual neuromodulators (ie, VIP – vasointestinal peptide and NO)
**Don’t send signals. Alter the response of other cells

Question 26

only amacrine cell with true axon?

Answer 26

interplexiform cell
(have an axon that sends back to the OPL to release dopamine which modulates gap junctions between cone synaptic endings and horizontal cell fibers)

Question 27

Neg feedback/lat inhibition amacrine cell function

Answer 27

Provide negative feedback and lateral inhibition at the ribbon synapses between bipolar cells and either magno-or parvo-cellular ganglion cells

Question 28

amacrine cells have: slow or fast responses?

Answer 28

rapid response

Question 29

Linking amacrine cells purpose?

Answer 29

Receive synaptic input from conventional size bipolar cells or other linking amacrine cells and synapse onto other linking amacrine cells in complex circuits or onto konio type ganglion cells.

Question 30

AII amacrine cells can synapse on what 2 things?

Answer 30

1) synaptic endings of on-center conventional size bipolar cells through gap junctions (excitatory)
2) synaptic endings of off-center conventional size bipolar cells (inhibitory)

Question 31

parvo gang cells receive synaptic input from:

Answer 31

midget bipolar cells

Question 32

konio gang cells receive synaptic input from:

Answer 32

diffuse bipolars >amacrine cells > more amacrine cells eventually get to konio cell

Question 33

target of parvo ganglion cells in brain:

Answer 33

layers 3-6 of LGN

Question 34

target of magno ganglion cells in brain:

Answer 34

layers 1 & 2 of LGN & to Superior Colliculus

Question 35

target of konio ganglion cells in brain:

Answer 35

many sites (LGN, SC and For circadian system, there are inputs to midbrain, inputs to areas for attention. They have different functions.) & Remember that the largest input is at pretectum

Question 36

2 types of melanopsin ganglion cells, both are turned on by light, and mostly from on-center diffuse bipolar cells (rods + cones), not just from own photopigment
WHAT IS THE DIFF BW THE TWO?

Answer 36

• One type receives synaptic input from the OPL

- One type receives synaptic input form the IPL