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Exercise 3: Neurophysiology of Nerve Impulses: Activity 1: The Resting Membrane Potential Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. What is the approximate concentration of K+ inside a typical cell (intracellular concentration)? You correctly answered: a. 150 mM 2. What is the approximate concentration of K+ outside a cell (extracellular concentration)? You correctly answered: b. 5 mM 3. What is the approximate concentration of Na+ inside a cell (intracellular concentration)? You correctly answered: b. 5 mM 4. What is the approximate concentration of Na+ outside a cell (extracellular concentration)? You correctly answered: a. 150 mM

04/09/12

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Experiment Results Predict Question: Predict Question: Predict what will happen to the resting membrane potential if the extracellular K+ concentration is increased. Your answer : b. The resting membrane potential will become less negative. Stop & Think Questions: What is the polarity of the resting membrane potential (voltage)? You correctly answered: b. negative What does it mean that the voltage just inside the membrane is negative? You correctly answered: b. There are more negative charges than positive charges just inside the membrane. The membrane of most cells, including neurons, contains passive, open, K+ leak channels. Given the normal K+ concentrations and the resultant concentration gradient, which direction would K+ be expected to move (diffuse) through these leak channels? You correctly answered: b. out of the cell What effect does increasing extracellular K+ have on the net diffusion of K+ out of the cell? You correctly answered: b. It decreases the net diffusion of K+ . Which way would Na+ move across the membrane if there were open Na+ channels? You correctly answered: a. Na+ would diffuse into the cell. The membrane has open K+ channels, and changing extracellular K+ concentration results in a change in membrane potential. Changing the...

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