Lecture4 - Lecture 4 Action Potentials I ion permeation ion...

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Unformatted text preview: Lecture 4 Action Potentials I ion permeation ion selectivity channel gating voltage-gated channels s ubstituted c ystene a ccessibility m easurements 6 membrane spanning domains 2 membrane spanning domains S4 = voltage-sensor positively charged residues sense membrane potential S4 generally hydrophobic +ve charges every third residue voltage sensor separate domain to core S4-S5 linker helix connects the two domains Closed Open Closed Open Closed v. fast fast v. slow slow Open Inactivated At Vm = -80 mV v. fast Closed Open Inactivated At Vm = +10 mV Kinetic Properties of Voltage-Gated Channels voltage-dependent rate constants V m-80 +10 Fraction open 0 - 1 - Closed v. fast fast v. slow slow Open Inactivated At Vm = -80 mV v. fast Closed Open Inactivated At Vm = +10 mV V m-80 +10 Fraction open 0 - 1 - Open Closed Inactivated N-type extracellular intracellular selectivity filter Open Closed Inactivated N-type extracellular intracellular selectivity filter Closed v. fast fast v. slow slow Open Inactivated At Vm = -80 mV v. fast Closed Open Inactivated At Vm = +10 mV Transient voltage change produced by varying ion conductances Voltage-gated potassium and sodium channels Action Potential Passive Membrane Properties RC circuit lipid bilayer = capacitor ion channels = resistor R C V m = I m x R R C Characteristics of the Action Potential 1. triggered by depolarization Depolarization Hyperpolarization Characteristics of the Action Potential...
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Lecture4 - Lecture 4 Action Potentials I ion permeation ion...

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