Lecture 9 - Neurons and Membrane Potential Spring 2010

Lecture 9 - Neurons and Membrane Potential Spring 2010 -...

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Long Distance Communication – Nervous System Resting Membrane Potential (Chapter 5, p. 164-171) Electrical Signals in Neurons (Chapter 8, p. 255-273) Neurotransmitter = (chemical signal) Electrical signals = transient and local changes in current flow in and out of cells that drives the voltage difference across the cell membrane away from its resting value (resting membrane potential). Graded potentials Action potentials
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Distribution of Water and Solutes 1) Water is able to distribute evenly throughout body - body at “Osmotic Equilibrium” 2) Movement of solutes restricted by transport properties of cell membrane – body is at “Chemical Disequilibrium” ECF ICF
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Inside Cell [Na + ] 15 mM [Cl - ] 10 mM Outside Cell [A - ] (Pr - ) 190 mM [K + ] 150 mM [Na + ] 150 mM [K + ] 5 mM [A - ] (Pr - ) 0.2 mM [Cl - ] 120 mM The Basis of the Resting Membrane Potential (Difference) Chapter 5, pages 164-171 [Ca 2+ ] 2.5 mM [Ca 2+ ] 0.001 mM - 70 mV ? mV
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Cell membrane Microelectrode inside cell Microelectrode outside cell Voltmeter + + + + + + + + + + + + + + + + + - - - - - - - - - - - - - - - - - - 70 mV Measuring Resting Potential Difference Across Cell Membrane 0 mV -70 mV
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Potassium Equilibrium Potential
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Potassium Equilibrium Potential K + K + 150 mM -90 mV 5 mM 0 mV Na + Na + The K+ concentration gradient shown is exactly opposed by a membrane potential of -90 mV. Therefore, -90 mV is the E K + or K + equilibrium potential.
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Equilibrium Potential Nernst equation calculates equilibrium potential for any ion: 61
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Lecture 9 - Neurons and Membrane Potential Spring 2010 -...

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