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9 Cards in this Set
- Front
- Back
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Rod Structure
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ROS - Outer segment - visual excitation
RIS - inner segment - synaptic and cellular functions |
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Rod Electrophysiology
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Dark - constant depolarization due to Na/K Atpase in RIS that pumps cations into the extracellular space - they flow into ROS due to open channels - upon photoactivation the channels close and hyperpolarization occurs.
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Peak Photoexcitation Time
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200 msec
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Rhodopsion
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Comprised of Opsin and Retinal - in Dark 11-cis retinal - in light all trans Retinal . It is a 7transmembrane G-Protein Receptor
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ROS channel Closure cascade
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Rhodopsin activated by light > activate cGMP PDE> hydrolysis of cGMP to 5'GMP> Decrease in cGMP > closure of channels in ROS
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Transducin in Photoexciation
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transmembrane G-protein. Alpha and Beta-gamma subunits. Latent form bound by GDP and bound to rhodopsin. Activated rhodopsin catalyzes GTP exchange on alpha su. Alpha-GTP binds to CGMP PDE and initiates hydrolysis of cGMP
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Rhodopsin Signal termination
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Change in light back to 11-cis rhodopsin > phosphorylation by Rhod. Kinase > Binding with Arrestin - (re-assocation with GDP-Transducin>no activation of cGMP PDE > cGMP in Cell > Opening of channels > depolarization ) NA/K channels open and restore membrane potential
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Phototransduction Neurotransmitter
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Glutamate - secreted during depolarization (dark and recovery)
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Color vision
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Due to color Opsin - diff binding for 11-cis retinal > diff response
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