NRSC 2100 1st Edition Lecture 17 Photoreceptors 1 Converts electromagnetic radiation to neural signals 2 Four main regions Outer segment disks photopigments Inner segment Cell body Synaptic terminal Two main types of photoreceptors Rods 1 and Cones 3 Regional Differences in Retinal Structure Varies from fovea to retinal periphery Peripheral retina High ratio of rods to cones High ratio of photoreceptors to ganglion cells More sensitive to light Regional Differences in Retinal Structure Cross section of fovea Pit in retina where outer layers are pushed aside Maximizes visual acuity These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Central fovea All cones no rods 1 1 ratio with ganglion cells Area of highest visual acuity Phototransduction Phototransduction in Rods Dark current Rod outer segments are depolarized in the dark because of steady influx of Na Photoreceptors hyperpolarize in response to light 1 Phototransduction in Cones Similar to rod phototransduction Different opsins Red green blue Color detection Contributions of blue green and red cones to retinal signal Spectral sensitivity Young Helmholtz trichromacy theory of color vision Retinal Processing 1 Only ganglion cells produce action potentials 2 Other retinal cells produce changes in membrane potentials 1 Photoreceptors release less neurotransmitter when stimulated by light 2 Influence horizontal cells and bipolar cells
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