Bipolar Cell Receptive Fields
The inotropic glutamate receptors of OFF bipolar cells, which are glutamate-gated sodium channels, mediate what kind of action in the cell?
A classical depolarizing excitatory postsynaptic potential
The depolarization of an OFF bipolar cell in the dark is due to the influx of ____
Sodium (Na+)
In the dark, when the photoreceptor of the receptive field center for an OFF-center bipolar cell is depolarized and releasing glutamate, the OFF-center bipolar cell will be depolarized and release more glutamate (the neurotransmitter of bipolar cells is the same as the neurotransmitter for photoreceptors), causing what to occur in the firing pattern of a corresponding OFF-center ganglion cell that the OFF-center bipolar cell synapses with?
The OFF-center ganglion cell that the OFF-center bipolar cell synapses with will have its firing rate increased
In the dark, when the photoreceptor of the receptive field center for an ON-center bipolar cell is depolarized and releasing glutamate, the ON-center bipolar cell will be hyperpolarized and release less glutamate (the neurotransmitter of bipolar cells is the same as the neurotransmitter for photoreceptors), causing what to occur in the firing pattern of a corresponding ON-center ganglion cell that the ON-center bipolar cell synapses with?
The ON-center ganglion cell that the ON-center bipolar cell synapses with will have its firing rate decreased
In addition to direct connections with photoreceptors, bipolar cells also are connected via horizontal cells to a circumscribed ring of photoreceptors that surrounds what?
The central cluster of photoreceptors that directly synapses with the bipolar cell
What makes the ON and OFF bipolar cells physically different?
The glutamate receptors on the membranes of the 2 bipolar cells
Bipolar cells are said to have ________ center-surround receptive fields
Antagonistic
The effect of horizontal cell hyperpolarization is to ______ the effect of light on the photoreceptors it is connected to.
Counteract
Disinhibited means _____
Depolarized
The receptive field center has ________ photoreceptor input
Direct
The opposite of facilitated is ______
Disfacilitated
Another word for facilitated is ______
Disinhibited
The opposite of inhibited is _____
Facilitated
In what layer do bipolar cells synapse with ganglion cells?
Inner plexiform layer
OFF bipolar cells have what kind of glutamate receptors?
Ionotropic glutamate receptors
If you had an OFF bipolar cell, hyperpolarization of the photoreceptor of its receptive field center (which would occur if light were shone onto the photoreceptor of its receptive field center) would result in the typical response---turn the OFF bipolar cell off. But, considering that bipolar cells have antagonistic center-surround receptive fields, hyperpolarization of the photoreceptors of its receptive field surround (which would occur if light were shone onto the photoreceptors of its receptive field surround) would result in the opposite response, turning the OFF bipolar cell on.
Is this right? Ask teachers
The hyperpolarization of an ON bipolar cell in the dark is due to the efflux of ______
Potassium (K+)
Inhibited means _____
Hyperpolarized
Hyperpolarization of the photoreceptor due to light causes less neurotransmitter (glutamate) to be released, resulting in a more ________ OFF bipolar cell
Hyperpolarized bipolar cell
When there is less glutamate being released, like in the light, what happens to ON bipolar cells?
They depolarize
The number of photoreceptors in a cluster that synapses with a bipolar cell ranges from ______ at the center of the fovea to ____ in the peripheral retina
1 at the center of the fovea to thousands in the peripheral retina
ON bipolar cells have what kind of glutamate receptors?
G-protein-coupled (metabotropic) receptors
The receptive field surround gets photoreceptor input via _________
Horizontal cells
When a photoreceptor hyperpolarizes in response to light, output is sent to _____ that also hyperpolarize
Horizontal cells
Another word for disfacilitated is ______
Inhibited
Amacrine cells have ______ connections in the inner plexiform layer
Lateral
The bipolar cells that hyperpolarize when light is shined onto a photoreceptor it is directly connected with are called ______ bipolar cells
OFF bipolar cells
OFF bipolar cells are ______ in the dark because of the present of glutamate and _______ in the light due to the lack of glutamate
OFF bipolar cells: - Facilitated in the dark - Disfacilitated in the light (inhibited, hyperpolarized)
OFF bipolar cells have what kind of receptive field centers and what kind of receptive field surrounds?
OFF receptive field centers and ON receptive field surrounds
The bipolar cells that depolarize when light is shined onto a photoreceptor it is directly connected with are called ______ bipolar cells
ON bipolar cells
ON bipolar cells are ______ in the dark because of the present of glutamate and _______ in the light due to the lack of glutamate
ON bipolar cells: - Inhibited in the dark - Facilitated in the light (disinhibited, depolarized)
ON bipolar cells have what kind of receptive field centers and what kind of receptive field surrounds?
ON receptive field centers and OFF receptive field surrounds
The response of a bipolar cell's membrane potential to light in the receptive field center is ______ to that of light in the receptive field surround
Opposite
Each single bipolar cell receives direct synaptic input from a single or a cluster of photoreceptors?
Receive direct synaptic input from a cluster of photoreceptors
The G-protein-coupled (metabotropic) receptors of ON bipolar cells mediate what kind of action in the cell?
Respond to glutamate by hyperpolarizing
The receptive field of a bipolar cell consists of what 2 parts?
The receptive field center and the receptive field surround
Example and explanation of lateral inhibition: Say we have a ON bipolar cell with a receptive field center, and light falling on this receptive field center will result in the depolarization of the ON bipolar cell (turn the ON bipolar cell on). The ON bipolar cell has a receptive field surround whose activation will result in the OPPOSITE response from the ON bipolar cell (in this case, activation of the receptive field surround would result in hyperpolarization of that ON bipolar cell, turning the ON bipolar cell off, even though normally the ON bipolar cell would be turned on when the photoreceptors are hyperpolarized in the light). The way this works is that the ON bipolar cell is connected to the receptive field surround via horizontal cells, and the job of horizontal cells is always to evoke the exact opposite of the response that a bipolar cell would normally have to light falling on the receptive field center.
We don't really know why this happens
Is the antagonistic center-surround receptive field organization passed on from bipolar cells to ganglion cells when they synapse in the inner plexiform layer?
Yes