Vision 3 Flashcards
What triggers a hyperpolarization in photoreceptor cells, which leads to decreased release of glutamate?
Light
Hyperpolarization in photoreceptors and decreased release of glutamate produces what?
Changes in bipolar membrane potentials, which triggers differential activity in ganglion cells.
Light stimulates rod and cone receptors, which activates which cells?
ON and OFF bipolar and ganglion cells.
What is the relationship of light and glutamate in rods and cones?
light inhibits glutamate release from rods/cones; darkness enhances it
_____ bipolar cells have glutamate receptors that respond to decreased glutamate with depolarization and excitation of the ganglion cell.
ON
Where are ON ganglion cells activated in the presence of light?
In the center of the RF
With darkness in the center of the RF, photoreceptors release more _____.
glutamate
____ bipolar cells have glutamate receptors that respond to increased glutamate with depolarization that excites the ganglion cells.
OFF
With no light, ____ bipolar-ganglion cells are excited.
OFF
WIth no light, _____ bipolar-ganglion cells are inhibited.
ON
There is an (active/inactive) response to darkness in the retina.
active
Each ganglion cell responds to light shining on the center of field _______ to that of peripheral field.
opposite
Which retinal ganglion cells respond to light spots surrounded by dark backgrounds like a star in a dark sky?
On-center retinal ganglion cells
Which retinal ganglion cells respond to dark spots surrounded by light backgrounds like a fly in a bright sky?
Off-center retinal ganglion cells
What CNS concept creates center-surround receptive fields?
Lateral inhibition
Which cells are activated by peripheral receptors and in turn reverse the activity of the receptors in the center?
Horizontal
When horizontal cells are activated by peripheral receptors, what do the center receptors do?
inhibit bipolar and ganglion cells
What does shining a light in the surrounding area activate?
horizontal cells that inhibit the ON cells that normally respond to light in the center. Note that it also stimulates OFF cells
Which cells inhibit center receptor cells, increasing the release of glutamate from the receptors and hyperpolarizing ON bipolar cells?
horizontal cells
What is the effect of horizontal cells inhibiting center receptor cells and increasing the release of glutamate from the receptors and hyperpolarizing ON bipolar cells?
The ON cells are thus inhibited and the OFF cells are excited
What is the function of center-surround fields?
enable ganglion cells to encode contrast
When do On- and off-center ganglion cells respond best?
when their receptive fields subtend light-dark edge.
What does the rate of activity of ganglion cells indicates?
amount of contrast between and center part of its receptive field.
Why does a moderately bright region may appear brighter or darker depending on the background?
Because ganglion cells enhance contrast
