01:830:331 Lecture Notes - Lecture 26: Opsin, Rhodopsin, Scotopic Vision
24 Jul 2016
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~the outermost part is the actual rod/cone part, called the outer segment . Has a bunch of folded lamellae with photopigments. Outermost on the eyeball, closest to the retina. ~inner segment is closer to outside world, has the rest of the cell body and nucleus. ~inner and outer segment are connected by cilium. Ex: in rods, we have rhodopsin, which is the rod opsin + retinal. ~when a molecule of rhodopsin is exposed to light, it breaks up into the rod opsin and the retinal. Its color changes to pale yellow, so we say that light bleaches the rhodopsin. This breaking up into opsin + retinal produces the receptor potential that causes hyperpolarization. ~note that photoreceptors are hyperpolarized in the presence of light (photopic) They depolarize in response to absence of stimulus, i. e. in the dark (scotopic) ~photoreceptors and bipolar cells do not make action potentials. They have graded potentials unlike action potentials, they are not all-or-none.
