Final answer:
Photoreceptor cells release glutamate in darkness and show graded hyperpolarization with different light levels. Light causes photoreceptors to hyperpolarize, reducing glutamate release and altering signal transmission through the retina to the brain. The correct option is 1.
Step-by-step explanation:
The cells that release glutamate in darkness and exhibit graded hyperpolarization in response to different luminance levels are the photoreceptor cells.
In the absence of light, photoreceptor cells (rods and cones) undergo tonic activity and are slightly depolarized, which enables them to release the neurotransmitter glutamate. This release of glutamate continuously inhibits the bipolar cells.
When light is present, it strikes the photoreceptors and causes a biochemical cascade that ultimately leads to the closure of sodium channels, resulting in the hyperpolarization of the photoreceptor cell membrane.
This hyperpolarization reduces the release of glutamate to the bipolar cells, which in turn, changes the activity in bipolar cells that connect to the retinal ganglion cells.
The ganglion cells then generate action potentials that are carried by their axons, forming the optic nerve, and consequently transmit visual information to the brain. The correct option is 1.