Action Potentials and Ion Channels Quiz - MCB160 Spring 2005, Assignments of Biochemistry

Download Action Potentials and Ion Channels Quiz - MCB160 Spring 2005 and more Assignments Biochemistry in PDF only on Docsity! Name:_______________________________ MCB160 Spring 2005 Quiz #2: Action Potentials and Ion Channels 1. Action Potentials: True or False a. Action potential conduction down the axon involves passive current flow. b. The spike initiation zone is the only place in the cell that an action potential can be initiated. c. Myelin increases the speed of action potential conduction by raising Cm. d. Myelin increases the speed of action potential conduction by raising Rm. e. The threshold for initiating an action potential is lowest in areas with a high density of K+ channels. 2. A genetic mutation in the chloride channel of muscle cells causes myotonia, which is a condition characterized by muscle hyper-excitability. Do you think the mutated channel is MORE or LESS permeable to chloride? Explain your answer in terms of membrane resistance and in terms of resting potential. 3. You stimulate a neuron and elicit an action potential, shown in the left graph below. Then you (foolishly) leave your prep sitting out while you go grab something to eat. Your (evil) labmate alters the external bath solution surrounding your cell, changing the concentration of a single ion. When you return from lunch, you stimulate your neuron with the exact same protocol as before, but you get the voltage response shown in the right graph. What ion did your labmate mess with? Did they raise or lower the concentration of that ion? 4. What is a ‘gating current’? Why isn’t it observed under normal conditions? Describe an experiment you could perform to measure the gating current, and draw sample current traces of what you would expect upon depolarizing and repolarizing the cell. -80 -40 0 40 Time Modified action potential -80 -40 0 40 Time Initial action potential mV