Final answer:
Retinal shape change initiates visual transduction in the retina. Activation of retinal and opsin proteins leads to a G protein activating and changing membrane potential, resulting in less neurotransmitter release. Bleaching occurs until retinal changes shape back to 11-cis-retinal.
Step-by-step explanation:
The shape change of retinal in the photoreceptors initiates visual transduction in the retina. Activation of retinal and the opsin proteins result in activation of a G protein. The G protein changes the membrane potential of the photoreceptor cell, which then releases less neurotransmitter into the outer synaptic layer of the retina. Until the retinal molecule is changed back to the 11-cis-retinal shape, the opsin cannot respond to light energy, which is called bleaching. When a large group of photopigments is bleached, the retina will send information as if opposing visual information is being perceived. After a bright flash of light, afterimages are usually seen in negative. The photoisomerization is reversed by a series of enzymatic changes so that the retinal responds to more light energy.