BPK 306 Chapter Notes -Resting Potential, Nernst Equation, Pericardial Fluid

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amethystworm242

1 Dec 2011

School

Simon Fraser University

Department

Biomedical Physio & Kines

Course

BPK 306

Professor

Mike Walsh

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Document Summary

Kin 305 tutorial #1 questions: why does a membrane potential exists in the cardiac myocytes. Action potentials require the membrane potential in order to exist. The membrane potential allows sodium ions to flow down the electrochemical gradient, commencing the ap. The membrane potential also exists due to different membrane permeability for potassium, sodium, and calcium ions. The high permeability for potassium ions allows more potassium efflux down a concentration gradient. The ventricle walls are 8-9 mm thick for the left ventricle; 3-4 mm for the right ventricle. The left ventricle needs to be thicker because it needs to pump blood out to various parts of the entire body, whereas the right ventricle is only pumping blood to the lungs. The permeability for k is highest because we need a very negative resting membrane potential. The nernst equation calculates the equilibrium potential for given amounts of intracellular, and extracellular ion concentrations for one particular type of ion.

Related Questions

Consider a typical cell at its resting membrane potential (rest Vm). The membrane temporarily becomes more permeable to Cl-.

Ecl = -65mV, resting Vm = -60mV

Does an electrical force (gradient) exist, if so in what direction? (.5 point)

What direction will the ion flow (said another way, what is the electrochemical gradient? (.5 point)

Would you expect the chloride equilibrium potential to change and if so, what direction will the change be? (.5 point)

If a cell were only permeable to one ion, would the Nernst potential for that ion (Ex) and the resting membrane potential be the same or different (if so how are they different)? (.5 points)

You are observing a cell at equilibrium with respect to the potassium cation (K+). The cell is in a bathing solution of 1 mM potassium, and you measure the membrane potential of the cell to be -118 mV. What is the internal potassium concentration? show steps

100 mM 10 mM 0.01 mM 1 mM 0.1 mM

Which of the following is NOT a characteristic of cardiacmembrane depolarization / polarization leading to generation of theaction potential?

a. The presence of a large amount of negative charges inside thecell creates a negative resting potential

b. There is a large amount of potassium inside the cells and alot of sodium outside, creating a membrane potential, which causesopening of Na and K channels, beginning membrane depolarization

c. Along with Na, a large amount of Cl ions also enter thecells, further creating a negative membrane potential

d. In order to restore the resting potential, a Na/K ATPAseremoves 3 Na for every 2 K it takes in from the cytosol, leavingless positive charges inside the cell, returning to a negativepotential

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BPK 306 Chapter Notes -Resting Potential, Nernst Equation, Pericardial Fluid

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