NEUR3112 Lecture Notes - Lecture 12: Receptive Field, Visual Phototransduction, Opsin
Document Summary
The photoreceptors convert, or transduce, light energy into changes in membrane potential. In the dark, a photoreceptor is depolarised at -30mv and when light hits it, it hyperpolarises. Glutamate is released in the dark, and when light hits, glutamate stops being released. Constant flow of na into the cell at rest cgmp opens the na channels. When light hits the opsins membrane potential drops -> cgmp breakdown. Rhodopsin is the photopigment in the membrane of stacked disks in the rod outer segments. Consists of opsin (receptor protein) and retinal (a small molecule derived from vitamin a) In light, retinal undergoes a change in conformation after absorbing the light, thereby activating, or bleaching, the opsin. Neur3112 - systems neuroscience page 1 thereby activating, or bleaching, the opsin. Literally changes colour from purple to a light yellow. This process is known as bleaching because it changes the wavelengths absorbed by rhodopsin (pigment changes from purple to yellow)
