Mechanism of generating visual signals: The retina adapts to change in light through the use of the rods. In the dark, the chromophore retinal has a bent shape called cis-retinal (referring to a "cis" conformation in one of the double bonds). When light interacts with the retinal, it changes conformation to a straight form called trans-retinal and breaks away from the opsin. This is called bleaching because the purified rhodopsin changes from violet to colorless in the light. At baseline in the dark, the rhodopsin absorbs no light and releases glutamate which inhibits the bipolar cell. This inhibits the release of neurotransmitters from the bipolar cells to the ganglion cell. When there is light present, glutamate secretion ceases thus no longer inhibiting the bipolar cell from releasing neurotransmitters to the ganglion cell and therefore an image can be detected.