3 OPL INL, IPL Flashcards
tonic release of NT by…
synaptic ribbon
rods and cones can by triggered by electrical synapses via
telodendria
how do cone-cone connections improve cone sensitivity?
- increase light capture
- average noise
- between RG cones
what do rod-cone connections do?
- allow rods to influence adjacent cones under mesopic conditions
- with blue cones
cells in rod endings?
- 2 horizontal cells
- 2 rod biploar
cells in cone endings?
- 2 horizontal cells
- 1 invaginating midget bipolar (IMB)
- 2 flat bipolar (FB)
- 2 flat midget bipolar (FMB)
horizontal cell types?
H1 - B
H2 - A
H3 - newest
H1 field/shape, dendrite and axon connections?
- small field size, stout dendrites bigger in periphery, fan-shaped axon
- more numerous than H2
- dendrite terminal contact cones
- axon contacts rod spherules
- only 1 contact with blue cone pedicle
H2 field/shape, dendrite and axon connections?
- spidery/wispy dendrites
- dendrites end in cone pedicles
- axons connect to many blue cone pedicles
H3 field size, dendrite and axon connections?
- appear like H1 but bigger dendritic trees, asymmetrical esp in periphery
- more cone pedicle connections
- no clear axon terminals
colour specific wiring of HC
- H1 - ML > S, rods
- H2 - S > ML
- H3 - ML, rods??
HC functions
- receive inputs and send opposite signals to PR
- mediate adaptation, contrast enhancement and colour opponency
bipolar cell types (12)
- 4 midget: red-on, red-off, green on, green off
- 6 diffuse: 3 on, 3 off (input from RG cones)
- 1 cone bipolar: blue-on
- 1 rod bipolar: on
http: //www.nature.com/nrn/journal/v5/n10/fig_tab/nrn1497_F2.html
do these cells overlap?
- horizontal cells
- bipolar cells
- HC - yes
- BC - no, but can share cone as input source
on and off bipolar cells have opposite responses to what? how are they different?
- respond oppositely to glutamate
- off-BC are sign-conserving - depolarise when cones depolarise (ionotropic or ligand-gated GluR)
- on-BC are sign-inverting - depolarise when cones hyperpolarise (metabotropic GluR)
describe midget bipolar cells
- fovea - input from 1 cone
- parafovea - dendritic arbours become larger
describe diffuse bipolar cells
- diffuse = contact multiple cones
- each of 6 types terminates at different layer (ones closest to GCL are on)
describe blue cone bipolar cells
- multiple inputs from blue cones only
- long dendrites
- on only
synapse with small bistratified GC (blue-on, yellow-off)
describe rod bipolar cells
- multiple inputs from rods only
- “mop” like dendrites
- on only
- don’t synapse GCs, they “piggy back” on AII amacrine
- AII inputs to on and off diffuse bipolar cells (input in sublamina B and output in sublamina A)
output of rod bipolar cells is to dyad: AII and A17 amacrine cells
- AII - common mammalian amacrine, small field, bistratified
- A17 - reciprocal amacrine, larger
what amacrine cells are strongly driven by the cone system?
A8 and A13
amacrine cell classification
- field size - narrow (30-150um), small (150-300um), medium (300-500nm, large (>500um)
- morphology
- NT type - GABAergic, glycinergic, both
amacrine NT and field size
- narrow - local glycine inhibition
- medium - local GABA inhibition
- wide - broad GABA inhibition
what are 3 kinds of inhibition?
- crossover inhibition
- lateral inhibition
- disinhibition
what’s crossover inhibition?
Crossover inhibition is characterized as OFF cells receiving ON inhibition and ON cells receiving OFF inhibition
what makes up a retinal hypercircuit unit in the IPL?
- bipolar cells
- 3 amacrines
- 1 ganglion cell
visual functions occur when release at on aren’t balanced by decrement in release at off
- when you want something asymmetrical
- rectification needed in non-linear movements
- crossover inhibition needed in linear compensation
when’s rectification needed?
- when you want something symmetrical
- local edge/texture detectors
- directional selectivity
when’s linearity needed?
looming detector
