PHGY 209 Lecture Notes - Lecture 10: Epithelium, Lateral Geniculate Nucleus, Lightdark
17 Mar 2017
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Retina: image comes to retina upside down brain inverts it, accommodation: Def: adjusting of lens to become fatter (more refraction) or thinner as object moves closer/further. How you focus depends on how far away the object is happens. Retina circuitry reverses this: reduction of nts increases activity of ganglion cells aps fired! High amplification single photon closes many na channels. Low sensitivity; day vision need more photons to. Low acuity; not present in central fovea; highly convergent many rods trigger single ganglion cell. Chromatic: 3 types of opsin see color! (62) In bright light, rods saturated & cones active move to dark: temporary blindness until rods take over & opsin + chromophore get back together: light adaption: In dark, cone inactive & rods active move to light: temp. blindness until cones take over & opsin & chromophore split up again. If shown uniform light, cells don"t care (cancels out)! They compare what"s in middle w/ outside: mechanism, some gang.
