WSU BIOLOGY 251 - Membrane Potential (5 pages)

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Membrane Potential



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Membrane Potential

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Lecture number:
4
Pages:
5
Type:
Lecture Note
School:
Washington State University
Course:
Biology 251 - Introductory Human Physiology
Edition:
1

Unformatted text preview:

BIO 251 1nd Edition Lecture 4 Outline of Last Lecture I Membrane composition and function II Membrane adhesions between different cells III Membrane transport IV Electrochemical gradients Outline of Current Lecture I Membrane potential II Action potentials III Neuron and the conduction of action potentials IV Graded Potential Current Lecture VI Membrane Potential A Overview 1 Definition a separation of electrical charge across a membrane 2 Because work is required to separate opposite charges already together separated charges have the potential to do work 3 Unit of measure is mV 1 1000 of a volt B All living cells have a membrane potential 1 Slight excess of positive charges on outside of cell 2 Slight excess of negative charges inside the cell 3 Ions responsible Na K Aa b Na and K are small enough to cross membrane through protein channels c A is too big to fit into protein channel and so can NOT cross membrane 4 Cells can have resting potentials between 5mV and 100 mV C Causes of Membrane Potential in Living Cells 1 Effect of K and A Fig 7 8 a Concentration gradient of K from ICF to ECF b So K diffuses out of cell through channels and A stays in cell These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute c Results in increase of electrical gradient as positive charges pile up outside and negative charges stuck inside d Continues until electrical gradient balances concentration gradient at 94 mV 2 Effect of Na and Cl Fig 7 9 a Concentration gradient of Na from ECF to ICF b So Na diffuses into cell through protein channels and Cl stays outside c Results in increase of electrical gradient as positve charges pile up inside and negative charges stuck outside d Continues until electrical gradient balances concentration gradient at 60 mV 3 Effect of Na K ATPase pump only a Pumps 3 Na out of cell for every two K pumped into cell b Creates a small membrane potential because



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