Lecture3BB - The action potential signal transport information The squid giant axon Ions Action Potential Gradient force Electrical force Resting

Lecture3BB - The action potential signal transport...

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Action Potential Resting Membrane Potential Ions “Gradient force” Electrical force Concentration gradients Semipermeable membrane pumps Change Membrane potential
Depolarization
Importance: The Nernst-Equilibrium Potentials (for all ions) are a “shortcut” for understanding ion movements (across the membrane). = RT ZF ln [ion] [ion] inside outside E ion x The Nernst-Equation
[K+]i = 300 mM [K+]o = 30 mM [A-] = 200 mM [Cl-]=102 mM [Cl-] = 50 mM [Na+] = 20 mM Ions that do not move will not be shown! Part 1 of the driving force: concentration gradients
[K]i = 300 mM [K]o = 30 mM = RT ZF ln [ion] [ion] inside outside E ion x Nernst 58 = Z log [ion] [ion] outside E ion inside E K = -58 mV concentration gradient for K+:
V= - 70 mV V= - 10 mV V= +58 mV V= + 90 mV A B C D [Na+]o = 450 mM [Na+]i = 45 mM - - - - - - + + + + + + Driving force = electrical force - concentration force
V= - 70 mV V= - 10 mV V= +55 mV V= + 90 mV A B C D [Na+]o = 450 mM [Na+]i = 50 mM - - - - - - + + + + + +
A - A - A - A - A - A - A - A - V= + 70 mV [Na+] [Na+] [K+] [K+] Sodium channels open: What direction ions are moving? always to change membrane potential towards their Nernst-potential!
The Goldman-Hodgkin-Katz Equation takes into account the relative permeabilities

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