retinal function Flashcards
what is difference between rod and cone system when contacting horizontal cells?
- in rod system there was a lot of convergence meaning lots of rods contact a single horizontal cell
- in cone system less convergence so less cones contact a single horizontal cell
what cells synapse with photoreceptors?
- horizontal cells synapse with photoreceptors and bipolar cells in the OPL
what are bipolar cells ?
- dendrites of bipolar cells synapse with photoreceptors and horizontal cells in the OPL
- have their cell body in the inner nuclear layer and send axons to the inner plexiform layer where bipolar cells synapse with amacrine cells, ganglion cells and interplexiform cells
where do bipolar cells have their dendrites?
OPL- where they synapse with photoreceptors and horizontal cells
where do bipolar cells have their synaptic processes ?
IPL- where they synapse with ganglion cells and amacrine cells
what are the two types of photoreceptors ?
rods and cones
how many types of horizontal cells do we have ?
3 types
DH1
DH2
DH3
how many types of bipolar cells ?
9 different bipolar cells in the human retina
what is rod bipolar cells ?
- type of bipolar cell that only contacts rods
- it receives input from 15-20 rods centrally and 40-50 rods in the periphery
- lots of convergence- many rods give information to a single bipolar cell
what are the other types of bipolar cells?
- all other bipolar cells are cone
- they synapse with a cone pedicle
what are the two general types of cone bipolar cells ?
- invaginating cone bipolar
- which end within triads
- form central element within triad - flat cone bipolar
- don’t go into the invaginations of the cone pedicle
- they make superficial contact with pedicles
why some types of bipolar cells called midget bipolar cell?
- small dendritic field meaning only contact single cones
what are the two types of midget bipolar cell?
- invaginating midget bipolar
- all of its dendrites form the central elements of the triads of just a single cone pedicle
- one to one relationship between cone pedicle and invaginating midget cell
- flat midget bipolar
- bipolar cell will contact a single cone in the central retina, forming superficial non-invaginating contacts
- in the cone system there is no convergence in central retina
summary of bipolar cell types ?
- there are 9 in the human retina
- 1 type of rod bipolar contacting many rods ( high convergence )
- 8 types of cone bipolar - which can be either flat or invaginating
- midget cone bipolar cells contact individual cones within the central retina ( no convergence )
what are amacrine cells?
- have their cell bodies in the lower half of the inner nuclear layer
- send dendrites into the inner plexiform layer where they synapse with bipolar cells and ganglion cells
- suited for mediating lateral interactions in the inner retina
- amacrine cells have no axon
where do most amacrine cells have their cell bodies?
most amacrine cells have their cell bodies within the INL and synapse in the IPL
how many types of amacrine cells ?
there are at least 25 different types in human