9.01 Recitation (R02) Recitation #2: Tuesday, September 18th Practice Exam Problems: From Brown Exam I 2000: 9. Ion X is negatively charged and more concentrated inside than outside of the cell. Therefore: (a) Ex is negative (b) EX is positive (c) EX is zero (d) The cell will fail its Olympic drug test 10. The resting membrane potential is closer to EK than ENa because at rest: (a) Vm – ENa = 0 (b) gNa = 0 (c) gK >> gNa (d) gK = 0 11. You discover an ion channel that, when open, is permeable to all ions. This channel lacks: (a) gating (b) quaternary structure (c) selectivity (d) an alpha subunit 14. Increasing extracellular K+ would lead to: (a) depolarization of the membrane (Vm becomes more negative) (b) depolarization of the membrane (Vm becomes less negative) (c) hyperpolarization of the membrane (Vm becomes more negative) (d) hyperpolarization of the membrane (Vm becomes less negative) 15. Increasing intracellular Na+ in a typical neuron would have what effect on ENa? (a) ENa would become more positive (b) ENa would become less positive (c) ENa would stay the same (d) That is not enough information to determine ENa 16. How would the mental pain caused by this exam be encoded as a neuronal signal? (a) By the amplitude of action potentials transmitted (b) By the duration of action potentials transmitted (c) By the frequency of action potentials transmitted (d) All of the above (e) None of the above 19. What would happen if the S4 domains of the voltagegated sodium channels important in action potential generation had their primary structure significantly altered? (a) Nothing important of interest (b) The action potentials generated would be of shorter duration (c) The gating properties of these channels would be disrupted (d) The channels will be phosphorylated 20. I. Axon diameter II. Axon myelination III. Axon length IV. Axonal membrane resistance Which of the above are important factors in the determination of action potential conduction velocity? (a) I only (b) I and II (c) I and III (d) I, II, IV (e) All of the above Answers: 9. B 10. C 11. C 14. B 15. B 16. C 19. C 20. D