neurophysiology-problems-revKEY _2_

neurophysiology-problems-revKEY _2_ - ++ channels open,...

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BIO172 Winter 2008 Problem Set: Neurophysiology The concentrations of ions outside (o) and inside (i) a neuron are shown below. ion out (mM) in (mM) Na + 130 13 K + 4 160 Cl - 100 10 Ca ++ 120 12 The Nerst equation is given below. The valence of these ions (z) is -1 or +1. The value of the remaining terms in the equation (2.3RT/F) is 58 mV at 20 degrees C. 1. 1. Calculate the equilibrium potentials for each ion. a. E Na+ = +58mV x log (130/13) = +58mV x log 10 = +58 mV b. E K+ = +58 mV x log (4/160) = +58mV x log (0.025) = +58 mV x -1.6 = -93 mV c. E Cl- = -58mV x log (100/10) = +58mV x log (10) = -58 mV d. E Ca++ = 58mV/2 x log (120/12) = 29 mV x log (10) = +29 mV 2. a. If the resting potential is -80 mV, the membrane is primarily permeable to what ion? K+ b. If the membrane potential becomes depolarized to - 20mV and Ca
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Unformatted text preview: ++ channels open, which way do the Ca ++ ions flow? into the cell E ion = 2.3 RT log [ion] o z F [ion] i 3. a. If you change the intracellular concentration of K + to 40 mM, what would the equilibrium potential for K + be? -58 mV b. How will this change in intracellular concentration of K + affect the E Na+ and E Cl ? No effect 4. You now record an action potential in this neuron. a. If the action potential is due to an influx of Na + , what is the maximum value that the membrane potential could reach at the peak of the action potential (assuming the membrane is impermeable to all other ions)? +58 mV b. If you change the outside concentration of Na + to 13 mM, what is the membrane potential at the peak of the action potential? 0 mV...
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This note was uploaded on 12/06/2009 for the course BIO 172 taught by Professor Clark during the Winter '08 term at University of Michigan.

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neurophysiology-problems-revKEY _2_ - ++ channels open,...

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