BS - Retina Part 2 - Week 3

Question 1

Are bipolar and amacrine cells evenly or unevenly distributed?

Answer 1

They are both evenly distributed.

Question 2

How many kinds of bipolar cells are there?

Answer 2

At least 10 different types.

Question 3

Describe rod bipolar cells and cone bipolar cells, and how many of each type of each there are. How many cells do each type contact?

Answer 3

Rod - one type only, contacts rods only

Cones - at least 10 types, contacts between 1 and 10 cones

Question 4

What is the ratio of rods to cones?

Answer 4

20 rods to 1 cone

Question 5

What neurotransmitter does the scotopic pathway use?

Answer 5

Glutamate

Question 6

Do rod bipolar cells directly contact ganglion cells?

Answer 6

No.

Question 7

How many rods do rod bipolar cells contact?

Answer 7

20-100

Question 8

Aside from rods, what cell type do rod bipolar cells contact, and how many?

Answer 8

Two types of amacrine cells.

Question 9

What is the most common type of amacrine cells? What signal do they feed into what pathway?

Answer 9

AII

They feed rod signals into cone pathways

Question 10

How many appendage types do amacrine type AII have, and what signal do they provide?
What kind of transmission pathway do they use?

Answer 10

Lobular - Off sublamina
Uses gap junctions - electrical synapse
Fine dendritic - On sublamina
Uses chemical (inhibitory) synapses
Uses glycine/GABA

Question 11

From how many cells does each rod bipolar cell receive input?
From how many cells does each AII amacrine cell receive input?
From how many cells does each ganglion cell receive input?
What is the purpose of this type of input system? From how many rod cells does a single ganglion cell receive input?

Answer 11

1 bipolar cell - 15 rod cell inputs
1 AII amacrine cell - 30 rod bipolar cell inputs
1 ganglion cell - 5 AII amacrine cell inputs
The goal is to increase sensitivity
Results in 1 ganglion cell receiving input from 1,500 rod cells.

Question 12

Describe the three kinds of cone cells.

Answer 12

S - sensitive to short wavelengths
M - sensitive to medium wavelengths
L - sensitive to large wavelengths

Question 13

Describe the two main retinal ganglion cell types, their size, and their percentage populations.

Answer 13

Midget ganglion cells - small soma/dendrites
-70%
Parasol ganglion cells
Large somas and dendrites
-8-10%

Question 14

Describe the ganglion synapses of the two ganglion cell types.

Answer 14

Inner nuclear layer
Inner plexiform layer
Off midget synapses
Off parasol synapses
On parasol synapses
On midget synapses
Inner plexiform layer
Ganglion cell layer
Midget cells are close to the border of the IPL, parasol cells are in the middle

Question 15

Describe the midget parvocellular pathway. Does it involve any convergence, and what kind of acuity does it provide?

Answer 15

Each midget ganglion cell receives input from one single cone via a single bipolar cell. No convergence.
High acuity as its 1:1:1

Question 16

Describe the midget parvocellular red/greenpathway.

Answer 16

Each cone contacts one On and one Off midget bipolar cell.

Question 17

Describe the parasol magnocellular pathway. Is this pathway involved in colour vision?

Answer 17

On/Off diffuse bipolar cells contact multiple cones (all types).
Off diffuse bipolar cells input to Off parasol cells.
On diffuse bipolar cells input to On parasol cells.
Parasol cells not involved in colour vision, used for motion detection.

Question 18

Humans have trichromacy. What is the cell population of the three cell types like?

Answer 18

S cone cells form less than 10% of cones.

M and L make the bulk.

Question 19

Describe the Blue-On/Yellow-Off pathway. What ganglion cell does it involve?

Answer 19

Involves small bistratified ganglion cells.
Bistratified, one synapse receives a Blue-On signal from a blue cone bipolar cell.
Other receives a Yellow-Off signal from an Off diffuse bipolar cell.
The Yellow-Off diffuse bipolar cell contacts red and green cones to form yellow.

Question 20

Is light distributed equally into parallel pathways?

Answer 20

Yes it is.

Question 21

Do rod bipolar cells directly contact ganglion cells?

Answer 21

No, they transmit via the cone pathway.