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9 Cards in this Set

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Rod Structure
ROS - Outer segment - visual excitation
RIS - inner segment - synaptic and cellular functions
Rod Electrophysiology
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.
Peak Photoexcitation Time
200 msec
Rhodopsion
Comprised of Opsin and Retinal - in Dark 11-cis retinal - in light all trans Retinal . It is a 7transmembrane G-Protein Receptor
ROS channel Closure cascade
Rhodopsin activated by light > activate cGMP PDE> hydrolysis of cGMP to 5'GMP> Decrease in cGMP > closure of channels in ROS
Transducin in Photoexciation
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
Rhodopsin Signal termination
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
Phototransduction Neurotransmitter
Glutamate - secreted during depolarization (dark and recovery)
Color vision
Due to color Opsin - diff binding for 11-cis retinal > diff response