Ch. 12

Question 1

1. Initiation of the action potential usually occurs _______of the neuron.
   a. in the cell body
   b. on the dendrites
   c. at the synapse
   d. on the axon
   e. at the axon initial segment

Answer 1

E

Question 2

2. Which of the following statements about an animal’s nervous system is false?
   a. Neurotransmitter is released throughout the body via the blood.
   b. Signal transmission rate is relatively fast.
   c. Neurons form highly discrete lines of communication.
   d. Action potential signals do not degrade over distance.
   e. A neuron must normally make synaptic contact with another cell in order to exert control.

Answer 2

A

Question 3

3. For a hormone to elicit a specific response from a cell, the cell must possess
   a. a synapse.
   b. integration.
   c. a cell body.
   d. dendrites specific to the hormone.
   e. receptor proteins specific to the hormone.

Answer 3

E

Question 4

4. Which of the following statements about the startle response of the cockroach is false?
   a. Vibrations of hairs generate nerve impulses in sensory neurons.
   b. Sound waves or air currents vibrate the filiform hairs.
   c. Sensory neurons synapse with and excite the dorsal hollow spinal cord.
   d. At the metathoracic ganglion, the interneurons synaptically excite leg motor neurons.
   e. The motor neurons activate leg muscles.

Answer 4

C

Question 5

5. Which of the following glial cells are found in the peripheral nervous system?
   a. Oligodendrocytes
   b. Schwann cells
   c. Astrocytes
   d. Both a and b
   e. Both a and c

Answer 5

B

Question 6

6. Which of the following statements about glial cells is false?
   a. They integrate cell membrane potentials to enhance or inhibit action potentials.
   b. They increase the velocity of nerve-impulse propagation.
   c. They act as metabolic intermediaries between capillaries and neurons.
   d. They help supply metabolic substrates to neurons.
   e. They mediate immune responses in neurons.

Answer 6

A

Question 7

7. The separation of positive and negative charges constitutes
   a. resistance.
   b. an electric current.
   c. a voltage.
   d. capacitance.
   e. a depolarization.

Answer 7

C

Question 8

8. Which of the following statements about membrane capacitance is false?
   a. It is in series with membrane resistance.
   b. In a cell, the membrane separates only similarly charged ions.
   c. It is measured in farads.
   d. It is a function of the insulating properties of the membrane.
   e. All of the above are true, none is false.

Answer 8

B

Question 9

9. What is occurring to the membrane?
   a. Depolarization
   b. Hyperpolarization
   c. Redistribution of charges during a current pulse
   d. Both a and c
   e. All of the above

Answer 9

D

Question 10

10. In the lower panel, the difference between the dashed line and the observed red line is due to
    a. membrane resistance.
    b. the fact that one represents a depolarization and the other represents a hyperpolarization.
    c. the difference in applied current pulses.
    d. the difference in applied voltage.
    e. the capacitive properties of the membrane.

Answer 10

E

Question 11

11. In the figure, the _______ decreases with distance.
    a. graded potential
    b. action potential
    c. membrane potential
    d. membrane current
    e. membrane capacitance

Answer 11

A

Question 12

12. Which of the following is the best explanation for the difference between the middle panel and the lower panel?
    a. The membrane in the lower panel is producing a lower current.
    b. There is a lower resistance in the lower panel at the point where voltage is measured.
    c. There is a greater capacitance in the lower panel at the point where voltage is measured.
    d. The membrane voltage measured in the lower panel is farther away from the current pulse.
    e. In the lower panel the action potential dissipates by the time it reaches the location of the electrode.

Answer 12

D

Question 13

13. The properties shown in the figure can be measured in which of the following?
    a. Neurons
    b. Pacemaker cells
    c. Muscle cells
    d. Both a and b
    e. All of the above

Answer 13

E

Question 14

14. Which of the following does not contribute to the passive electrical properties of a cell?
    a. Membrane resistance
    b. Membrane capacitance
    c. The time constant
    d. Length constants
    e. The resting membrane current

Answer 14

E

Question 15

17. Which of the following is not a factor in the Nernst Equation?
    a. The gas constant, R
    b. Capacitance
    c. Temperature
    d. The valence of the ion species
    e. The ion concentrations on the two sides of the membrane

Answer 15

B

Question 16

18. In a cell, the difference in ion concentration between the intracellular and extracellular fluids results from
    a. active ion transport.
    b. passive diffusion of ions.
    c. bulk movements of intracellular and extracellular fluids.
    d. Both a and b
    e. All of the above

Answer 16

D

Question 17

19. According to the Nernst equation, which of the following will depolarize Vm, the membrane potential?
    a. A decrease in temperature
    b. An increase in the valence of the ion species involved
    c. A decrease in the electromotive force of the ion
    d. A decrease in the concentration of anions inside the membrane
    e. An increase in Faraday’s constant

Answer 17

D

Question 18

20. Which of the following statements regarding the ions in intracellular and extracellular fluids is false?
    a. Na+ leaks into the cell rapidly because its electrochemical gradient is large.
    b. K+ leaks out of the cell slowly because the electrochemical gradient is small.
    c. Cl– may be at passive equilibrium in some cells.
    d. The Na+‒K+ pump actively transports Na+ out of the cell and K+ into the cell.
    e. All of the above are true, none is false.

Answer 18

A

Question 19

21. According to the Goldman equation, the contribution of each ion to the membrane potential depends the most on
    a. its size.
    b. its membrane permeability.
    c. its activation energy.
    d. temperature.
    e. the resting membrane potential.

Answer 19

B

Question 20

22. Which of the following is most responsible for the all-or-none property of the action potential?
    a. Myelination
    b. Voltage-gated K+ channels
    c. Voltage-gated Na+ channels
    d. Leakage of K+ channels
    e. Acetylcholine

Answer 20

C

Question 21

30. For an axon at resting membrane potential, the K+ leak channel is _______, the voltage-gated Na+ channel is _______, and the voltage-gated K+ channel is _______.
    a. open; inactivated; closed
    b. closed; inactivated; closed
    c. open; inactivated; open
    d. closed; closed; closed
    e. open; closed; closed

Answer 21

E

Question 22

31. During the falling phase of an action potential, the K+ leak channel on the axon is _______, the voltage-gated Na+ channel is _______, and the voltage-gated K+ channel is _______.
    a. open; inactivated; closed
    b. closed; inactivated; closed
    c. open; inactivated; open
    d. closed; closed; closed
    e. open; closed; closed

Answer 22

C

Question 23

38. Which of the following statements about a voltage clamp of a neuron to 0 mV is false?
    a. Once clamped, the voltage remains at 0 mV.
    b. Voltage-gated potassium channels open.
    c. Apart from the initial current shift from the clamp, no other current is produced.
    d. Voltage-gated sodium channels open
    e. An inward ionic current is produced during the opening of voltage-gated sodium channels.

Answer 23

C

Question 24

39. Which of the following statements regarding the structure of the voltage-gated Na+ channels is false?
    a. P loops mediate ion selectivity.
    b. Segment 4 of each domain is the voltage sensor.
    c. It has 4 domains with extensive sequence homology.
    d. The channel protein changes its primary structure in response to membrane depolarization.
    e. A cytoplasmic loop is thought to inactivate the channel by blocking the opening.

Answer 24

D

Question 25

40. Which of the following is a shared characteristic between a spiking neuron and a nonspiking neuron?
    a. High concentration of voltage-gated Na+ channels at the axon hillock
    b. The Hodgkin cycle
    c. A graded potential down the entire length of the axon
    d. An action potential down the entire length of the axon
    e. Neurotransmitter secretion based on a change in membrane potential

Answer 25

E

Question 26

41. How do nonspiking neurons function even though their depolarization signal significantly degrades with distance?
    a. Voltage-gated Na+ channels are replaced by ligand-gated Na+ channels.
    b. These neurons are very short, so there is no major signal decrement.
    c. There are sufficient numbers of voltage-gated Na+ channels to convey the signal without major decrement.
    d. These neurons do not release neurotransmitters, so signal degradation is not a problem.
    e. Voltage-gated K+ channels compensate for the lack of voltage-gated Na+ channels.

Answer 26

B

Question 27

45. Which of the following is the best explanation for the absolute refractory period of the action potential?
    a. Inactivated voltage-gated sodium channels
    b. Closed voltage-gated sodium channels
    c. Open slow calcium channels
    d. Inactivated voltage-gated potassium channels
    e. The passive properties of the axon membrane

Answer 27

A

Question 28

46. Which of the following statements about a local circuit in an axon is false?
    a. Na+ ions move into the cell through open Na+ channels.
    b. Ions flow in intracellular fluid, carrying current to more distant parts of the membrane.
    c. At the membrane, the ion movements change the distribution of charges on the membrane capacitance.
    d. An ionic current completes the local circuit as cations move toward the locus of the action potential and anions move away.
    e. Anions migrate into the membrane interior.

Answer 28

E

Question 29

47. _______ prevents bidirectional propagation of action potentials.
    a. The inactivation of Na+ channels
    b. The increased permeability to K+
    c. A decrease in membrane resistance
    d. Myelination
    e. The K+ channel

Answer 29

A

Question 30

48. Conduction velocity shows a(n) _______ axon diameter.
    a. proportional relationship to
    b. proportional relationship to the square root of
    c. exponential relationship to
    d. Either a or b, depending on the type of axon
    e. Either a or c, depending on the type of axon

Answer 30

D

Question 31

49. Which of the following is not one of the likely factors affecting the various velocities at which axons conduct action potentials?
    a. Myelination
    b. Temperature
    c. Length
    d. Diameter
    e. The number of voltage-gated Na+ channel per unit surface area

Answer 31

C

Question 32

50. Myelination by Schwann cells increases the velocity of action potential propagation by
    a. increasing the resistance and decreasing the capacitance, allowing the action potential to “jump” over the myelinated area.
    b. decreasing the resistance and increasing the capacitance, allowing the action potential to “jump” over the myelinated area.
    c. increasing the diameter of the neuron.
    d. increasing the number of voltage-gated sodium channels.
    e. increasing the resistance and increasing the capacitance, allowing the action potential to “jump” over the myelinated area.

Answer 32

A

Question 33

1. The neuron converts an electrical signal to a chemical signal in the
   a. dendrite.
   b. presynaptic terminal.
   c. axon.
   d. cell body.
   e. axon hillock.

Answer 33

B

Question 34

2. Neurons that relay sensory signals to integrative centers of the CNS are called
   a. interneurons.
   b. synaptic neurons.
   c. efferent neurons.
   d. afferent neurons.
   e. motor neurons.

Answer 34

D

Question 35

3. Which of the following is not a type of glial cell?
   a. Schwann cells
   b. Oligodendrocites
   c. Astrocytes
   d. Microglial cells
   e. Neurocytes

Answer 35

E

Question 36

4. Which term best describes the movement of ions across a membrane?
   a. Current
   b. Voltage
   c. Resistance
   d. Capacitance
   e. Membrane potential

Answer 36

A

Question 37

5. A decrease in the absolute value of the membrane potential toward zero is called
   a. depolarization.
   b. an action potential.
   c. hyperpolarization.
   d. a membrane potential.
   e. voltage.

Answer 37

A

Question 38

6. Which of the following does not contribute to the cell’s membrane potential?
   a. Permeability to K+
   b. Permeability to Na+
   c. The overall resistance of the membrane
   d. Electrogenic ion pumps
   e. None of the above; all contribute to membrane potentials.

Answer 38

E

Question 39

7. The time constant (τ) depends on the
   a. resistance of the membrane.
   b. capacitance of the membrane.
   c. resistance and voltage of the membrane.
   d. resistance and capacitance of the membrane.
   e. resistance, capacitance, and voltage of the membrane.

Answer 39

D

Question 40

8. If a current pulse is generated on the membrane and creates a passive potential, which of the following will be true?
   a. The change in the membrane potential will increase as the distance from the current pulse increases.
   b. The change in the membrane potential will decrease as the distance from the current pulse increases.
   c. The change in the membrane potential will remain constant throughout the length of the membrane.
   d. The change in the membrane potential will fluctuate depending on the strength of the initial current pulse.
   e. There will be no change in membrane potential.

Answer 40

B

Question 41

9. The plasma membrane of a resting neuron is most permeable to which of the following ions?
   a. Na+
   b. K+
   c. Cl–
   d. Ca2+
   e. Mg2+

Answer 41

B

Question 42

10. Which of the following would not occur if ouabain was used to block Na+–K+-ATPase pumps?
    a. Na+ would go to equilibrium across the cell membrane.
    b. The membrane potential would become less negative.
    c. The concentration of K+ would be equal on both sides of the membrane.
    d. The cell would no longer be in a steady state.
    e. Cl– would go to equilibrium across the cell membrane.

Answer 42

C

Question 43

11. In a typical neuron, which of the following ions is in passive equilibrium across the cell membrane?
    a. Na+
    b. K+
    c. Cl–
    d. Both Na+ and K+
    e. Both Na+ and Cl–

Answer 43

C

Question 44

12. A stimulating depolarizing current that depolarizes the axon hillock just slightly negative to the threshold will
    a. not change the overall membrane potential at all.
    b. produce an action potential.
    c. produce a very small action potential.
    d. produce a temporary graded potential.
    e. produce a small action potential that increases in amplitude as it travels along the axon.

Answer 44

D

Question 45

13. _______ channels govern the generation of an action potential.
    a. Ligand-gated Na+
    b. Ligand-gated K+
    c. Voltage-gated Na+
    d. Voltage-gated K+
    e. K+

Answer 45

C

Question 46

14. Considering the cycle of an action potential, when is the permeability to K+ at its greatest?
    a. During the resting membrane potential
    b. During the rising phase of the action potential
    c. At the peak of the action potential
    d. During the falling phase of the action potential
    e. The permeability of K+ remains the same throughout the action potential cycle.

Answer 46

D

Question 47

15. Which of the following statements regarding the action potential is false?
    a. In an extremely long axon, the action potential eventually will degrade.
    b. During the “falling” phase, K+ permeability increases.
    c. During the “rising” phase, Na+ moves into the neuron.
    d. The action potential lasts about 3 ms.
    e. In the recovery phase, Na+ channels are closed.

Answer 47

A

Question 48

16. What allows the action potential to return to a repolarized state?
    a. K+ leaks into cells.
    b. Voltage-gated Na+ channels become inactivated.
    c. Voltage-gated K+ channels become inactivated.
    d. Na+ reaches equilibrium across the neural membrane and stops leaking in.
    e. Voltage-gated Na+ channels close.

Answer 48

B

Question 49

17. Which of the following statements regarding cardiac pacemaker cells is false?
    a. They spontaneously generate action potentials.
    b. The frequency of action potential generation can be modified by neural input.
    c. The pacemaker cells are modified neural tissue.
    d. They are connected to myocardium via gap junctions.
    e. They have a current that is inward and activated by hyperpolarization.

Answer 49

C

Question 50

18. _______ are responsible for extending the time of the cardiac action potential relative to a neural action potential.
    a. Slow Ca2+ channels
    b. Slow Na+ channels
    c. Slow frequency of action potentials to the pacemaker
    d. Slow K+ channels
    e. Voltage-gated Na+ channels

Answer 50

A

Question 51

19. Which of the following is not likely to affect the conduction velocity of an action potential?
    a. Axon diameter
    b. Myelination
    c. Membrane surface area to volume ratio
    d. Temperature
    e. None of the above; all affect the velocity of an action potential.

Answer 51

E

Question 52

20. In myelinated axons, action potentials occur
    a. all along the axon.
    b. only at the internodes.
    c. only at the initial segment of the axon.
    d. at the internodes and nodes of Ranvier.
    e. only at the nodes of Ranvier.

Answer 52

E