handout 2 - Biology 365R Handout for Discussion on Monday,...

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Biology 365R Handout for Discussion on Monday, Sept. 14 and Thursday, Sept. 17 Objectives : To understand the origin of the resting membrane potential in terms of concentration gradients and selective membrane permeabilities. To understand the Bernstein theory of the ori- gin of the resting membrane potential and its deficiencies. To understand the necessary role of the Na-K pump. To know the Nernst and Goldman-Hodgkin-Katz equations and how to use them. To know and understand some experiments showing the origin of the resting membrane potential. To understand the voltage clamp, how it works and how it shows us the conductances that underlie the action potential. To understand the concept of threshold and how it relates to ionic movements. To understand the patch clamp and what it shows us about the behavior of in- dividual proteins in the membrane, and how the behavior of individual channels can be recon- ciled with the behavior of the entire cell. Please note, that due to the labor day holiday, there will be no discussion sessions held next week! Discussion questions : 1. List the factors that contribute to the resting membrane potential. How can this potential be measured? Explain the existence of the injury current observed by DuBois-Reymond. Predict the direction of the current observed (note you will have define whether you’re talking about the movement of + or – charge; by convention, physiologists define current as the movement of + ions, even though the movement might be of – ions in the opposite direction). 2. What is the experimental evidence supporting the idea that it is the movement of K that primarily accounts for the generation of the resting membrane potential? Describe how you would conduct such an experiment. Describe experiments you could conduct that would sug- gest the role of other ions. 3. What would be the expected consequence for the resting membrane potential of reversing the ions and their concentration inside and outside a nerve? 4. If a cell were permeable only to calcium and the calcium concentration ratio outside to inside were 100, what membrane potential would be expected at equilibrium? What if the cell were permeable only to chloride and the concentration ratio outside to inside were 10? What if the cell were permeable only to potassium ions and the ratio outside to inside were 10? 5.
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handout 2 - Biology 365R Handout for Discussion on Monday,...

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