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NACS641-10L3 - Propagation of electrical signals in neurons...

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Ricardo C. Araneda [email protected] Fall 2010 Propagation of electrical signals in neurons and the action potential Some drawings are from “The neuron; cell and molecular Biology” Levitan & Kaczmarek Friday, September 10, 2010
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OVERVIEW: * Action potentials * Phases of the action potential * Voltage-clamp * Ion currents underlying the AP * Structure of Na channels * Na channel inactivation * Axon and dendrites as wires (previous lecture) * Gating current Friday, September 10, 2010
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Membranes are permeable to more than one ion _ Cl + Na + K _ Cl + K + Na The Goldman-Hodgkin-Katz equation Permeability; how easy is for ions to cross the membrane Friday, September 10, 2010
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The cell membrane as an electrical circuit Ionic membrane current I i Capacitive membrane current I c I m = I i + I c Membrane current = I m Friday, September 10, 2010
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“Small cell” “Large cell” Current -2 pA Current -20 pA R in 1 G Ω R in 200 M Ω Why do we care? Friday, September 10, 2010
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Real Neurons How are signals affected by the passive properties of the membrane ? Friday, September 10, 2010
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Experiment 3 Local potentials are graded resting potential Almost no change in potential is observed, why? Friday, September 10, 2010
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r a axial resistance ( Ω /cm) Current pulse r a r m r m membrane resistance ( Ω cm ) Section of axon or dendrite of determined length (x). In this case 1 cm.
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