Chapter 2

27. During the overshoot phase of an action potential, membrane potential briefly reaches a value near _______ mV. a. -80 b. -65 c. 0 d. +50 e. +90

d. +50

6. Which stimulus is most likely to evoke an action potential? a. Small hyperpolarizing current pulse b. Large hyperpolarizing current pulse c. Small depolarizing current pulse d. Large depolarizing current pulse e. Microelectrode insertion

d. Large depolarizing current pulse

22. There is an excess of _______ in the extracellular compartment, relative to the intracellular compartment. a. Na + only b. K + only c. Na + and Ca 2+ only d. Na + and Cl - only e. Na + , Cl - , and Ca 2+

e. Na+, Cl-, and Ca2+

16. In a two-compartment model of a cell with a K+-permeable membrane and a 10-fold excess of K+ in the inside compartment, how would K+ ions flow across the membrane? a. They would flow from the inside compartment to the outside compartment. b. They would flow from the outside compartment to the inside compartment. c. There would be no flow of K + ions. d. They would flow in both directions at the same time in equal molar quantities. e. They would flow in both directions, but the flow would be negligible.

a. They would flow from the inside compartment to the outside compartment.

2. The resting membrane potential typically ranges from _______ to _______. a. -90 mV; 90 mV b. 40 mV; 90 mV c. 40 V; 90 V d. -40 mV; -90 mV e. 0 mV; 90 mV

d. -40 mV; -90 mV

5. The amplitude of the action potential of a given neuron is a. larger in response to depolarizing currents of greater magnitude. b. dependent on the magnitude of the sensory stimulus. c. related to the number of synapses on the neuron. d. smaller if the resting potential of the neuron is lower. e. always the same.

e. always the same.

4. How will a neuron respond to an injection of negative current? a. It will become hyperpolarized. b. It will have a positive electrical response. c. It will generate a single action potential. d. It will generate multiple action potentials. e. It will reach the threshold potential.

a. It will become hyperpolarized.

21. Concentrations of which ion, inside and outside of a neuron, have the greatest effect on the resting membrane potential? a. K + b. Na + c. Ca 2+ d. Cl - e. PO 4 3-

a. K+

24. Which experimental model did Hodgkin and Katz use in their studies of the resting membrane potential? a. Living squid neuron b. Neurons of Aplysia species c. Mammalian neurons d. Mammalian brain slices e. Neurospheres

a. Living squid neuron

25. Which state of the plasma membrane does not occur during an action potential? a. Resting phase b. Rising phase c. Overshoot phase d. Falling phase e. Undershoot phase

a. Resting phase

18. Under which circumstances is the Goldman equation equivalent to the Nernst equation? a. When a membrane is permeable to only one ion b. When a membrane is permeable to multiple ions c. When the membrane is permeable to positively charged ions only d. When the membrane is permeable to negatively charged ions only e. When permeability of the membrane is different for different ions

a. When a membrane is permeable to only one ion

23. Hodgkin and Katz discovered that the resting membrane potential changes by _______ mV per tenfold change in K+ concentration. a. +29 b. +58 c. +65 d. +90 e. +119

b. +58

14. In a two-compartment model of a cell with a K+- and Ca2+-permeable membrane and a 10-fold excess of K+ in the inside compartment, how would the membrane potential change if all K+ ions were replaced by Ca2+ ions? a. It would double. b. It would be reduced by half. c. It would not change. d. It would become positive. e. No potential would be generated.

b. It would be reduced by half.

26. During which phase of an action potential does membrane permeability to Na+ exceed membrane permeability to K+? a. Rising phase only b. Rising and overshoot phases c. Overshoot phase only d. Overshoot and falling phases e. All of the phases of the action potential

b. Rising and overshoot phases

17. In a two-compartment model of a cell with a K+-permeable membrane and a 10-fold excess K+ in the inside compartment, the membrane potential is experimentally made more negative than the K+ equilibrium potential. How would K+ ions flow across the membrane? a. They would flow from the inside compartment to the outside compartment. b. They would flow from the outside compartment to the inside compartment. c. There would be no flow of K + ions. d. They would flow in both directions at the same time in equal molar quantities. e. They would flow in both directions, but the flow would be negligible.

b. They would flow from the outside compartment to the inside compartment.

10. Which statement best describes the Nernst equation? a. It relates the equilibrium potential of an ion to its intracellular concentration. b. It relates the equilibrium potential of an ion to its extracellular concentration. c. It relates the equilibrium potential of an ion to its intra- and extracellular concentrations. d. It relates the equilibrium potentials of multiple ions to their intracellular concentrations. e. It relates the equilibrium potentials of multiple ions to their intra- and extracellular concentrations.

c. It relates the equilibrium potential of an ion to its intra- and extracellular concentrations.

13. In a two-compartment model of a cell with a K+- and Na+-permeable membrane and a 10-fold excess of K+ in the inside compartment, how would the membrane potential change if all K+ ions were replaced by Na+ ions? a. It would double. b. It would be reduced by half. c. It would not change. d. It would become positive. e. No potential would be generated.

c. It would not change.

19. The resting potential of a cell is negative because a. there is an excess of K + outside of the cell at rest. b. at rest there is an excess of K + outside of the cell, and the membrane is permeable chiefly to K + . c. at rest there is an excess of K + inside the cell, and the membrane is permeable chiefly to K + . d. at rest there is an excess of K + inside the cell, but the membrane is permeable to all ions. e. there is an excess of Cl - ions outside of the cell at rest.

c. at rest there is an excess of K+ inside the cell, and the membrane is permeable chiefly to K+.

3. An action potential occurs if current injected into a neuron _______ the neuron to reach _______ potential. a. depolarizes; synaptic b. hyperpolarizes; synaptic c. depolarizes; threshold d. hyperpolarizes; threshold e. hyperpolarizes; resting

c. depolarizes; threshold

11. In a two-compartment model of a cell with a K+-permeable membrane, at K+ equilibrium potential, there is _______ flux of K+ ions. a. a large inward b. a large outward c. no net d. a small inward e. a small outward

c. no net

8. What is the mechanism of action of most local anesthetics? a. Hyperpolarize resting membrane potential of neurons b. Block glutamate receptors in excitatory synapses c. Enhance the activity of inhibitory synapses by acting on postsynaptic GABA receptors d. Block Na + channels involved in the generation of action potentials e. Bind opiate receptors

d. Block Na+ channels involved in the generation of action potentials

15. In a two-compartment model of a cell with a K+- and Cl--permeable membrane and a 10-fold excess of K+ in the inside compartment, how would the membrane potential change if all K+ ions were replaced by Cl- ions? a. It would double. b. It would be reduced by half. c. It would not change. d. It would become positive e. No potential would be generated.

d. It would become positive

20. How does membrane permeability to K+ (PK) and Na+ (PNa) change during an action potential? a. P Na always exceeds P K ; permeability does not change for either ion. b. P K always exceeds P Na ; permeability does not change for either ion. c. P Na exceeds P K at rest; P K temporarily increases during the action potential. d. P K exceeds P Na at rest; P Na temporarily increases during the action potential. e. P K exceeds P Na at rest; P Na increases during the action potential and remains higher than P K until the next action potential, then it quickly drops.

d. PK exceeds PNa at rest; PNa temporarily increases during the action potential.

12. In a two-compartment model of a cell with a K+-permeable membrane and a 10-fold excess of K+ in the inside compartment, how would the membrane potential change if all K+ ions were replaced by Na+ ions? K + ions were replaced by Na + ions? a. It would double. b. It would be reduced by half. c. It would not change. d. It would become positive. e. No potential would be generated.

e. No potential would be generated.

1. Which type(s) of electrical signals occur(s) within the neural circuit for a spinal reflex? a. Receptor potential only b. Action potential only c. Synaptic potential only d. Receptor potential and action potential only e. Receptor potential, synaptic potential, and action potential

e. Receptor potential, synaptic potential, and action potential

9. Which statement about active ion transporters is true? a. They are selectively permeable to certain ions. b. They are functionally similar to ion channels. c. They allow ion movement down the concentration gradient. d. They move all ions against the concentration gradient. e. They move certain ions against the concentration gradient.

e. They move certain ions against the concentration gradient.

7. Subthreshold current injected into an axon flows _______ along the axon and _______ with a. actively; remains constant b. actively; decays c. actively; grows d. passively; remains constant e. passively; decays

e. passively; decays