Chapter 10 Pt. 2 (Part 5) Flashcards
what are the two types of bipolar cells?
ON and OFF
what are the two types of glutamate receptors?
ionotropic or metabotropic
what does depolarization of a bipolar cell trigger?
graded potential which releases glutamate from the bipolar cell onto the retinal ganglion cell
what triggers a graded potential which releases glutamate from the bipolar cell onto the retinal ganglion cell?
depolarization of a bipolar cell
what are the only cells of the visual system that can fire an action potential?
ganglion cells
how do we interpret things as different colors and shapes?
different combinations of action potentials coming through the optic nerve
ionotropic cation channel =
OFF bipolar cell
G protein-coupled receptor =
ON bipolar cell
OFF bipolar cell =
ionotropic cation channel
ON bipolar cell =
G protein-coupled receptor
what do ionotropic glutamate receptors (fast ligand-gated ion channels) do when glutamate binds?
ALWAYS DEPOLARIZE
what happens when a-subunit binds to multivalent Na+/Ca+2 channels?
closes the channel to cause metabotropic bipolar cell to hyperpolarize and stop releasing glutamate onto the RGC
what do metabotropic glutamate receptors (G protein) do when glutamate binds?
ALWAYS HYPERPOLARIZE!
what happens to a metabotropic receptor on the bipolar cell in the dark
photoreceptor releases glutamate onto it
why are OFF bipolar cells called OFF?
they are depolarized when the light is off in the center
why are ON bipolar cells called ON?
because they depolarize when the light is on in the center
what happens if light strikes the center field but not the surround?
AP frequency is even less.
center is inhibited by both light and GABA so glutamate release is about 0
when is AP frequency highest for OFF bipolar cells?
when light is OFF in the center and ON in the surround
when does AP frequency decrease for OFF bipolar cells?
when light hits the entire RF and decreases even more when ON in the center and OFF in the surround
will ON hyperpolarize or depolarize when glutamate binds?
hyperpolarize
what happens to a hyperpolarized bipolar cell?
it will not stimulate RGC to fire an AP
when is AP frequency lowest in ON bipolar cells?
light is off in the center and on in the surround
increases when light strikes the entire receptive field
when is AP frequency the highest in ON bipolar cells?
light is ON in the center and OFF in the surround
why can’t you see immediately when you go from light to dark?
rhodopsin in all of the disks in rods will be photo bleached
not enough light to activate any of the cones
