Chapter 6b Membrane potential

Chapter 6b Membrane potential - Membrane potential...

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Membrane potential Diffusion of an ion Equilibrium potential Membrane potential
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1. Diffusion of an ion
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2A. Equilibrium potential for sodium (E Na )
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Equilibrium potential Consider sodium ions. [Na + ] out > [Na + ] in 1. If the membrane is permeable to Na + , then more Na + enters from the outside than leaves from the inside. 2. The inside develops a net excess of + charge over – charge. 3. The excess + charge inside acts like “pressure” against the entry of more + ions, including Na + . This electric pressure is measured in millivolts (mV), positive inside with respect to outside. (By convention, the outside is always assigned the value 0.) 4. The excess of + charge inside (and the positive voltage it generates) increases up to the point that the rate of the efflux of Na + (due to the positive voltage ) from the interior equals the rate of influx (due to the concentration gradient ) into the interior. 5.
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Chapter 6b Membrane potential - Membrane potential...

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