NEUROSCI 223 Midterm: ProblemSet4_MembraneExcitability+Key
7 Apr 2016
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Question 1: action potentials: draw what happens to the membrane potential as you inject current as shown in a, B, and e. parts c and d have been completed for you as an example: label any passive responses and action potentials. A and b show downward passive currents, with b greater than. There"s a threshold for depolarization, and that action potentials are all-or-nothing. Question 3: membrane excitability: ions are important: you stimulate a neuron, and then measure the membrane potential further down the axon. You get a trace that looks like this. Should be no transient depolarization; blocks sodium channels. On the same plot, draw the resulting voltage trace. Be sure to label which trace is which. Assuming extracellular sodium concentration [na+]out is 500mm, and intracellular sodium concentration [na+]in is 50mm, use the following equation for to calculate the reversal potential for sodium:
