BIO2A03-2011-L20 - Biol 2A03 - 2011 Lecture 20 3 Basic...

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Biol 2A03 - 2011 Lecture 20
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3 Basic Principles of Membrane Potentials 3. Most membrane potentials are associated with 3 factors : (i) Unequal distribution of ions across membranes. (ii) An active transport mechanism which maintains/restores this unequal distribution - e.g. Na + , K + ATP-ase pump. (iii) Differential permeability of the membrane to different ions Note: for ions, the electrical analogue of permeability is Conductance = 1/Resistance = G 2
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The Resting Membrane Potential Inside Neuron Outside Neuron 3 Na + 2 K + Electrogenic Na + /K + -ATPases i) move more “+” charge outside cell. ii) move K + and Na + against gradient to maintain unequal distribution across membrane. -70mV RESULT: negative resting membrane potential Na + K + G K + >> G Na + :this means that more K + leaves the cell than Na + entering the cell. This differential permeability of the membrane to K + and Na + leads to more “+” charge leaving cell. K + K + Na + Cl - Na + A - (Organic anions) 3
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both sodium and potassium into cell K outflow slows down, Na inflow speeds up -membrane potential stabilizes Na/K – ATPase counteracts leakage to maintain gradients
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BIO2A03-2011-L20 - Biol 2A03 - 2011 Lecture 20 3 Basic...

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