【多选题】Why is a rod photoreceptor cell from the retina exquisitely sensitive to light?
A.
The light-absorbing rhodopsin proteins are embedded in many pancake-shaped vesicles (discs) of membrane inside the outer segment of the photoreceptor cell.
B.
When the rod cell is stimulated by light, a signal is relayed from the rhodopsin molecules in the discs, through the cytosol, to ion channels that allow positive ions to flow through the plasma membrane of the outer segment.
C.
These cation channels close in response to the cytosolic signal, producing a change in the membrane potential of the rod cell.
D.
By mechanisms similar to those that control neurotransmitter release in ordinary nerve cells, the change in membrane potential alters the rate of neurotransmitter release from the synaptic region of the cell. Released neurotransmitters then act on retinal nerve cells that pass the signal on to the brain.