Final answer:
The phototransduction cascade involves a series of steps that occur in the photoreceptor cells of the retina. When light hits the retinal molecule, it undergoes a shape change, initiating a signaling pathway. This ultimately leads to changes in membrane potential and neurotransmitter release.
Step-by-step explanation:
The steps in the phototransduction cascade involve a series of events that occur in the photoreceptor cells of the retina. When light hits the retinal molecule, it undergoes a shape change, activating the opsin protein and initiating a signaling pathway. This leads to the activation of a G protein, which changes the membrane potential of the photoreceptor cell. As a result, less neurotransmitter is released into the outer synaptic layer of the retina. The retinal molecule must be changed back to its original shape before the opsin can respond to light energy again. This process is called bleaching.
To reverse the photoisomerization, enzymatic changes occur in a series of steps so that the retinal can respond to more light energy. It is important to note that when a large group of photopigments is bleached, the retina may send information as if opposing visual information is being perceived, leading to the afterimages that are usually seen in negative after a bright flash of light.