Zoo/Psych/Neuro 523 Problem set 5 answers 2008 1). Why does the myelin sheath make the action potential propagate faster? Myelin increases the transmembrane resistance of the axon, and decreases its capacitance. The increased membrane resistance means that the inward current at an active node will be funneled down the axon further than if there is no myelin. This brings a more distant site on the axonal membrane to threshold. 2). How would you show that the after-hyperpolarization following an action potential is due to potassium movement? The easiest way is to change Ek by changing the external K ion concentration and record the relationship between the amplitude of the after-hyperpolarization and Ek. 3). If the voltage-sensitive sodium inactivation mechanism is destroyed with pronase applied to the inside of an axon, how is the action potential changed? When pronase is applied to the inside of the axon the action potential will become longer (more time to reach the resting potential). This is because the inactivation gate on the sodium channels has been
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This note was uploaded on 03/26/2010 for the course ZOOLOGY 523 taught by Professor Stretton during the Fall '08 term at University of Wisconsin.