PHGY 209 Lecture Notes - Lecture 19: Opsin, Chromophore, Rhodopsin

• School: McGill University
• Department: Physiology
• Course: PHGY 209
• Professor: Alvin Shrier

Document Summary

Billions of them in the discs to increase the chances of capturing photons. Chromophore (inside opsin): allows proteins to be sensitive (breaks apart) to a photon. Induces a conformational change in the opsin, which then activates a g protein cascade which are an engine floating round in the discs. They convert cgmp to gmp and the sodium channels close (hyperpolarizing the membrane) causing photoreceptors to reduce the neurotransmitter release. Cgmp: activates cgmp-gates channel lining the membrane of the outer segment. When neurons are depolarized, is releases neurotransmitter (even in the dark) 4 different opsin molecules (rhodopsin is found in the rods) Low acuity: not present in central fovea, highly. In bright light, rods are saturated, and cones are active. In dark light, temporary blindness until rods take over. In the dark, cones are inactive, and rods are active. In the bright light, temporary blindness until cones take over.