Retinal Physiology Flashcards
PRs are slightly depolarized relative to a typical neuron. What is the resting membrane potential of a PR?
-50mV
In the dark, what 2 things happen to PRs?
- Release glutamate
2. Depolarized
In the light, what 2 things happen to PRs?
- No glutamate released
2. Hyperpolarized
What % of rhodopsin must be bleached to have a critical number of sodium channels closed?
10%
PRs show what type of potential?
Graded potential - degree of PR hyperpolarization is related to intensity of stimulus
PRs synapse with what 2 inhibitory cells in the OPL?
- Bipolar Cells
2. Horizontal Cells
What two cells send retinal info horizontally? Are these cells excitatory or inhibitory?
Horizontal and amacrine cells
- inhibitory
Lateral connections provide feedback transmission of information via what pathway?
Centrifugal pathway (from gang. cells to PRs)
Horizontal cells receive input from what cell?
One or more PR
Horizontal cells send information to what cell?
Bipolar cells - may also be innervated directly by other PRs
What inhibitory neurotransmitter do horizontal cells release in response to DEPOLARIZATION of PRs?
Gaba
H1 Horizontal cells primarily receive input from what PR?
M and L Cones
This type of horizontal cell regulates adaptation and spatial responses of cones and bipolar cells
H1
T/F: H1 cells connect to cones in its dendritic field and rods at its most distal end
True
H2 horizontal cells receive input from all 3 types of cones. Do they connect to rods?
No, do not connect to rods
What 2 types of cells show a graded response?
PRs and Horizontal Cells
PRs and Horizontal Cells both HYPERPOLARIZE in response to light. What is this called?
Sign-conserving synapses
This is the region of visual space that makes a neuron change its firing under the presence of a certain visual stimulus.
Retinal receptive field
A bipolar dendrite synapses with what 2 cells?
PRs and Horizontal cells
Dendrite = BPH, dicks
A bipolar axon synapses with what 2 cells?
Ganglion, Amacrine Cells
Axon = BAG
What neurotransmitter is released from bipolar cells?
Glutamate
Bipolar cells receive extensive synaptic feedback from what cell?
Amacrine cells
What are the 4 kinds of bipolar cells?
- Rod bipolar
- Midget bipolar
- Diffuse bipolar
- S-cone bipolar
This type of bipolar cells does not contact ganglion cells directly. They’re mediated by amacrine or cone bipolar cells
Rod bipolar cells (only 1 kind)
In the central/mid-peripheral retina, this bipolar cell contacts only 1 cone. In the peripheral retina, this cell has input from more than 1 cone.
Midget bipolar cell (M or L input)
In the central retina, this bipolar cell contacts about 5 neighboring cones, and in peripheral retina about 10-15.
Diffuse bipolar cell
This type of bipolar cell is a short wavelength cone.
S-cone bipolar cell
Bipolar cells generate what type of potential?
Graded potential
Bipolar cells were the first to display ___ ____
Spatial antagonism
If the bipolar cell depolarizes in response to less glutamate, what type of cell is this?
on-center cell
- excited by light
- releases glutamate
If the bipolar cell hyperpolarizes in response to less glutamate, what type of cell is this?
off-center cell
- inhibited by light
- doesn’t release gluta.
On-center bipolar cells synapse with ganglion cells in what layer of the IPL?
Inner sublayer (invagination synapse in
Off-center bipolar cells synapse with ganglion cells in what layer of the IPL?
Outer sublayer
The center response in bipolar cells comes directly from?
PRs
The surround response comes indirectly from?
Horizontal cells
What neurons were the first in the visual system to fire action potentials and generate transient responses?
Amacrine Cells
The short and sweet response of Amacrine cells help do what 2 things?
- Code movement
2. Detect Change
This is when the ganglion cells are always active, even when not stimulated. Sends signals from 5-40/sec.
Spontaneous Activity/ Maintained discharge
Ganglion cells produce what type of potential?
Full action potentials
On/Off center bipolar cells synapse with
On/Off center ganglion cells, respectively.
On/Off center midget bipolar cells synapse with ?
On/Off center midget ganglion cells (parvo cells/p-cells)
On/Off center diffuse bipolar cells synapse with?
On/Off center parasol ganglion cells (magno cells/M-cells)
Midget (parvo) GCs are found where?
in the fovea
What layers of the LGN do p-cells project to?
Parvocellular layers
These ganglion cells are color sensitive, have high spatial resolution, poor temporal resolution and a sustained response to light
P-Cells, Midget Ganglion cells
Input for the m-cells come from what cells?
Rods
What layers of the LGN do m-cells project to?
Magnocellular layers
This type of ganglion cell has good temporal resolution, is sensitive to motion and has a transient response to light.
Parasol ganglion cells (M-cells)
The opposite effects of light on the center and surround is called:?
Spatial Antagonism/Lateral inhibition
What 2 cells cause an action potential?
Amacrine and Ganglion
What layer of the LGN do small, bistratified ganglion cells project to?
Konio layer
