BS - Retina Part 2 - Week 3 Flashcards
Are bipolar and amacrine cells evenly or unevenly distributed?
They are both evenly distributed.
How many kinds of bipolar cells are there?
At least 10 different types.
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?
Rod - one type only, contacts rods only
Cones - at least 10 types, contacts between 1 and 10 cones
What is the ratio of rods to cones?
20 rods to 1 cone
What neurotransmitter does the scotopic pathway use?
Glutamate
Do rod bipolar cells directly contact ganglion cells?
No.
How many rods do rod bipolar cells contact?
20-100
Aside from rods, what cell type do rod bipolar cells contact, and how many?
Two types of amacrine cells.
What is the most common type of amacrine cells? What signal do they feed into what pathway?
AII
They feed rod signals into cone pathways
How many appendage types do amacrine type AII have, and what signal do they provide?
What kind of transmission pathway do they use?
Lobular - Off sublamina Uses gap junctions - electrical synapse Fine dendritic - On sublamina Uses chemical (inhibitory) synapses Uses glycine/GABA
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?
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.
Describe the three kinds of cone cells.
S - sensitive to short wavelengths
M - sensitive to medium wavelengths
L - sensitive to large wavelengths
Describe the two main retinal ganglion cell types, their size, and their percentage populations.
Midget ganglion cells - small soma/dendrites -70% Parasol ganglion cells Large somas and dendrites -8-10%
Describe the ganglion synapses of the two ganglion cell types.
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
Describe the midget parvocellular pathway. Does it involve any convergence, and what kind of acuity does it provide?
Each midget ganglion cell receives input from one single cone via a single bipolar cell. No convergence.
High acuity as its 1:1:1
Describe the midget parvocellular red/greenpathway.
Each cone contacts one On and one Off midget bipolar cell.
Describe the parasol magnocellular pathway. Is this pathway involved in colour vision?
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.
Humans have trichromacy. What is the cell population of the three cell types like?
S cone cells form less than 10% of cones.
M and L make the bulk.
Describe the Blue-On/Yellow-Off pathway. What ganglion cell does it involve?
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.
Is light distributed equally into parallel pathways?
Yes it is.
Do rod bipolar cells directly contact ganglion cells?
No, they transmit via the cone pathway.
