10+ Year Member
7+ Year Member
Jun 11, 2007
Medical Student (Accepted)
I am kind of confused regarding visual processing.

I know the anatomy of the eye, and how the retina contains cones and rods. Each rod and cone contains a light-absorbing retinal bounded to an opsin (membrane protein), forming rhodopsin and photopsin respecitvely. I also know that rods and cones synapse with bipolar cells, which synapse with ganglion cells, which carry the signal to the optic nerve. What I am confused about is what role does glutamate play? The book I am studying from says that "in the dark, rods and cones are depolaried, and they continually release glutamate at these synapses. The steady glutamate release in the dark depolarizes some bipolar cells, and hyperpolarizes others, depending on the type of posynaptic receptor molecules they contant." If two different types of responses are happening, how is information communicated? Also, how is it possible for rods and cones to react the same to light when they have different functions in interpreting light.

I guess my major point of confusion is the bipolar cell. Also, what is the role of horizontal and amacrine cells?