Ch.6 Ionic Basis Of The Resting Potential Exam Questions - From Neuron to Brain 6e | Test Bank Martin by A. Robert Martin. DOCX document preview.
Chapter 6: Ionic Basis of the Resting Potential
Test Bank
Type: multiple choice question
Title: Chapter 06 Question 01
1. Which is a requirement for a neuron to remain in a stable condition?
Feedback: Subhead: A Model Cell
Learning Objective: List the three major requirements for a cell to remain in a stable condition.
Bloom’s Level: 2. Understanding
a. It must have equal concentrations of intracellular sodium and potassium.
b. It must be osmotically balanced.
c. It must have a small sodium permeability to counteract the sodium-potassium exchange pump.
d. It must have a small chloride permeability to counteract the potassium permeability.
e. The intracellular solution must be electrically negative compared to the extracellular solution.
Type: multiple choice question
Title: Chapter 06 Question 02
2. Which is true of the potassium equilibrium potential?
Feedback: Subhead: A Model Cell
Learning Objective: Explain what the potassium equilibrium potential (EK) is.
Bloom’s Level: 4. Analyzing
a. In neurons, it is usually around 70mV.
b.It describes the membrane potential at which all ionic movement stops.
c. It predicts the membrane potential when the neuron is at steady state.
d. It is the membrane potential where electrical forces and concentration gradients are equal and opposite.
e. It plays little or no role in setting the resting membrane potential.
Type: multiple choice question
Title: Chapter 06 Question 03
3. Which must be true for an ion to be at equilibrium?
Feedback: Subhead: A Model Cell
Learning Objective: Explain what the potassium equilibrium potential (EK) is.
Bloom’s Level: 3. Applying
a. The concentrations on both sides of the membrane must be equal.
b. The electrical gradient must match the concentration gradient in the opposite direction.
c. The neuron’s membrane potential must be negative.
d. The neuron’s membrane potential must be positive.
e. The permeability of the ion must be zero.
Type: multiple choice question
Title: Chapter 06 Question 04
4. In a model cell, positive ions collect on the outer surface of the cell membrane, while anions collect along the inner surface. These ions are effectively removed from the intracellular and extracellular solutions, leaving these solutions
Feedback: Subhead: A Model Cell
Learning Objective: Explain why the charge separation across the membrane of a model cell (e.g., one that is permeable only to potassium and chloride) does not violate the principle of electrical neutrality.
Bloom’s Level: 3. Applying
a. electrically charged.
b. osmotically balanced.
c. ion-deficient.
d. electrically neutral.
e. osmotically imbalanced.
Type: multiple choice question
Title: Chapter 06 Question 05
5. Increasing the extracellular potassium concentration causes chloride ions to
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. flow into the cell.
b. flow out of the cell.
c. accumulate in the extracellular space.
d. redistribute to establish equal concentrations on both sides of the cell membrane.
e. do nothing; extracellular potassium concentration does not impact chloride ions.
Type: multiple choice question
Title: Chapter 06 Question 06
6. When a neuron is at rest, the cell membrane is permeable mostly to
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. potassium
b. sodium
c. anions
d. calcium
e. all of the above
Type: multiple choice question
Title: Chapter 06 Question 07
7. The resting membrane potential for a neuron will depolarize (become less negative) with increased extracellular concentration of which of the following ions?
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. Potassium
b. Sodium
c. Chloride
d. Calcium
e. Anions
Type: multiple choice question
Title: Chapter 06 Question 08
8. In a model cell at rest, what is the relative concentration of potassium inside the cell?
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. Lower than the concentration of potassium outside the cell
b. The same as the concentration of potassium outside the cell
c. Higher than the concentration of potassium outside the cell
d. Lower than the sodium concentration inside the cell
e. Lower than the concentration of anions inside the cell
Type: multiple choice question
Title: Chapter 06 Question 09
9. The intracellular concentration of sodium in a neuron is
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. much lower than the extracellular concentration.
b. somewhat lower than the extracellular concentration.
c. the same as the extracellular concentration.
d. somewhat higher than the extracellular concentration.
e. much higher than the extracellular concentration.
Type: multiple choice question
Title: Chapter 06 Question 10
10. At rest, potassium ions exhibit very low current because the tendency for potassium to flow across the cell membrane because of a concentration gradient is opposed by
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. chloride ions moving across the cell membrane because of a concentration gradient.
b. sodium ions moving across the cell membrane because of a concentration gradient.
c. potassium ions moving across the cell membrane because of the electrical gradient.
d. chloride ions moving across the cell membrane because of the electrical gradient.
e. sodium ions moving across the cell membrane because of the electrical gradient.
Type: multiple choice question
Title: Chapter 06 Question 11
11. What happens in a model cell when the extracellular chloride concentration is lowered to half its original value?
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. The membrane potential gets more positive (depolarizes).
b. The membrane potential gets more negative (hyperpolarizes).
c. The membrane potential stays about the same.
d. The equilibrium potential for potassium gets more negative.
e. The equilibrium potential for potassium gets more positive.
Type: multiple choice question
Title: Chapter 06 Question 12
12. What happens in a squid giant axon when the extracellular potassium concentration is increased?
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. The membrane potential gets more positive (depolarizes).
b. The membrane potential gets more negative (hyperpolarizes).
c. The membrane potential stays about the same.
d. The equilibrium potential for sodium gets more negative.
e. The equilibrium potential for sodium gets more positive.
Type: multiple choice question
Title: Chapter 06 Question 13
13. What happens in a squid giant axon when the extracellular chloride concentration is increased?
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. The membrane potential gets more positive (depolarizes).
b. The membrane potential gets more negative (hyperpolarizes).
c. The membrane potential stays about the same.
d. The equilibrium potential for sodium gets more negative.
e. The equilibrium potential for sodium gets more positive.
Type: multiple choice question
Title: Chapter 06 Question 14
14. For a cell at rest, increasing the extracellular sodium ion concentration will cause what movement of sodium ions?
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration
Bloom’s Level: 2: Understanding
a. Sodium ions will move out of the cell.
b. Sodium ions will move into the cell.
c. Sodium ions will move away from the cell in the extracellular space.
d. Sodium ions will not move because the cell is at equilibrium.
e. Sodium ions will not move because sodium ions cannot cross the cell membrane.
Type: multiple choice question
Title: Chapter 06 Question 15
15. For a cell at rest, increasing the extracellular potassium ion concentration will cause what movement of potassium ions?
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. Potassium ions will move out of the cell.
b. Potassium ions will move into the cell.
c. Potassium ions will move away from the cell in the extracellular space.
d. Potassium ions will not move because the cell is at equilibrium.
e. Potassium ions will not move because potassium cannot cross the cell membrane.
Type: multiple choice question
Title: Chapter 06 Question 16
16. For a cell at rest, increasing the extracellular chloride ion concentration will cause what movement of chloride ions?
Feedback: Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 2. Understanding
a. Chloride ions will move out of the cell.
b. Chloride ions will move into the cell.
c. Chloride ions will move away from the cell in the extracellular space.
d. Chloride ions will not move because the cell is at equilibrium.
e. Chloride ions will not move because chloride ions cannot cross the cell membrane.
Type: multiple choice question
Title: Chapter 06 Question 17
17. What happens when the axoplasm is removed from the giant axon of the squid?
Feedback: Subhead: Membrane Potentials in the Squid Axon
Learning Objective: Discuss two factors that make the squid giant axon a model system for studying membrane potentials.
Bloom’s Level: 2. Understanding
a. Intracellular and extracellular ionic solutions can be controlled and the axon responds normally.
b. Anions removed from the intracellular space are lost and the axon loses function.
c. Ions from the extracellular space move inward, and the axon has a positive resting potential.
d. Ionic concentration can no longer be measured.
e. The membrane produces a weak potential that decays over time.
Type: multiple choice question
Title: Chapter 06 Question 18
18. Which of the following is true regarding the sodium permeability for a cell at rest?
Feedback: Subhead: Membrane Potentials in the Squid Axon
Learning Objective: Explain what the effect of sodium permeability is on membrane potential.
Bloom’s Level: 2. Understanding
a. The sodium permeability is about the same as the potassium permeability.
b. The sodium permeability is about 50% smaller than the potassium permeability.
c. The sodium permeability is about 75% smaller than the potassium permeability.
d. The sodium permeability is about 90% smaller than the potassium permeability.
e. The cell membrane is not permeable to sodium at rest.
Type: multiple choice question
Title: Chapter 06 Question 19
19. What is the purpose of the constant field equation?
Feedback: Subhead: The Constant Field Equation
Learning Objective: Explain what the constant field equation is.
Bloom’s Level: 2. Understanding
a. To determine the equilibrium potential of a single ion
b. To determine the membrane potential when potassium and chloride are present.
c. To determine the resting potential of a cell given all ionic concentrations and conductances
d. To determine which ions are moving across the membrane at rest
e. To determine the minimum voltage at which ionic movement can be balanced
Type: multiple choice question
Title: Chapter 06 Question 20
20. Which of these conditions is assumed under the constant field equation?
Feedback: Subhead: The Constant Field Equation
Learning Objective: Describe the general principle illustrated by the constant field equation.
Bloom’s Level: 4. Analyzing
a. Equal conductance for sodium and potassium
b. Zero net ionic current
c. High chloride conductance
d. High potassium conductance
e. Low sodium conductance
Type: multiple choice question
Title: Chapter 06 Question 21
21. Ionic conductance is a measure of
Feedback: Subhead: The Constant Field Equation
Learning Objective: Describe the general principle illustrated by the constant field equation.
Bloom’s Level: 2. Understanding
a. the electrical charge of an ion.
b. the charge strength of an ion.
c. the resistance of an ion to movement.
d. the equilibrium potential of an ion.
e. how easily the ion can move across the membrane.
Type: multiple choice question
Title: Chapter 06 Question 22
22. The driving force on an ion is defined as the difference between the
Feedback: Subhead: The Constant Field Equation
Learning Objective: Describe the general principle illustrated by the constant field equation.
Bloom’s Level: 2. Understanding
a. membrane potential and the threshold potential.
b. conductance of an ion and the membrane potential.
c. membrane potential and the equilibrium potential for that ion.
d. fraction of ions on the intracellular and extracellular membranes.
e. sodium and potassium equilibrium potentials.
Type: multiple choice question
Title: Chapter 06 Question 23
23. For a membrane potential to remain stable, which of the following must be true?
Feedback: Subhead: The Constant Field Equation
Learning Objective: Describe the general principle illustrated by the constant field equation.
Bloom’s Level: 2. Understanding
a. The potassium conductance must be equal to zero.
b. The sum of all ionic currents must be equal to zero.
c. The chloride and potassium equilibrium potentials must be the same.
d. The chloride and sodium currents must be equal.
e. The chloride and potassium conductances must be equal.
Type: multiple choice question
Title: Chapter 06 Question 24
24. In a cell at rest, the driving force on sodium is high, while the permeability of sodium is low. As a consequence, which of the following is true of the cell’s membrane potential at rest?
Feedback: Subhead: The Constant Field Equation
Learning Objective: Describe the general principle illustrated by the constant field equation.
Bloom’s Level: 4. Analyzing
a. Sodium ion concentrations have a small influence on the resting membrane potential.
b. Small changes in extracellular sodium concentration will have a large impact on the membrane potential.
c. Sodium is at equilibrium at the resting membrane potential.
d. Small changes in the intracellular sodium concentration will have a large impact on the membrane potential.
e. Sodium ion concentrations do not contribute to the resting membrane potential.
Type: multiple choice question
Title: Chapter 06 Question 25
25. The membrane potential of a cell depends on the relative conductances of the membrane to the major ions, and on the
Feedback: Subhead: The Constant Field Equation
Learning Objective: Describe the general principle illustrated by the constant field equation.
Bloom’s Level: 4. Analyzing
a. permeability of these ions.
b. charge of these ions.
c. concentrations of these ions.
d. size of these ions.
e. equilibrium potentials of these ions.
Type: multiple choice question
Title: Chapter 06 Question 26
26. At the neuron’s resting membrane potential, chloride ions are at equilibrium; what else must be true?
Feedback: Subhead: The Constant Field Equation
Learning Objective: Describe the general principle illustrated by the constant field equation.
Bloom’s Level: 4. Analyzing
a. The driving forces on sodium and potassium are equal and in opposite directions.
b. The concentrations of sodium and potassium are equal on opposite sides of the membrane.
c. The permeability of the membrane to sodium and potassium are equal.
d. The ratio of sodium to potassium is equal on opposite sides of the membrane.
e. The products of the driving force and permeability for sodium and potassium are equal and opposite.
Type: multiple choice question
Title: Chapter 06 Question 27
27. In the term “steady state,” what is steady?
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Explain the concept of steady state.
Bloom’s Level: 3. Applying
a. The net passive loss of solutes from the cell
b. The composition of the cytoplasm
c. The leaking of solutes into the cell
d. The activity of ion pumps
e. The direction in which sodium and potassium are moving
Type: multiple choice question
Title: Chapter 06 Question 28
28. In order to maintain the neuronal membrane potential at steady state, which must occur?
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Explain the concept of steady state.
Bloom’s Level: 4. Analyzing
a. ATP must be produced and used by the cell.
b. The potassium conductance must be low.
c. The membrane must be impermeable to sodium.
d. The sodium current must be zero.
e. The chloride equilibrium potential must be less than that for potassium.
Type: multiple choice question
Title: Chapter 06 Question 29
29. Which of these is not a factor in determining the membrane potential for a cell?
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Name the four factors on which the resting membrane potential depends.
Bloom’s Level: 4. Analyzing
a. The concentration of sodium ions inside and outside the cell
b. The concentration of potassium ions inside and outside the cell
c. The relative permeability (or conductance) of the membrane to sodium and potassium ions
d. The ratio of the actions of the sodium-potassium exchange
e. The type of cell being studied (e.g., glia, muscle, neuron)
Type: multiple choice question
Title: Chapter 06 Question 30
30. The action of the sodium-potassium exchange pump is electrogenic. What does this mean?
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Explain how the sodium–potassium exchange pump maintains a cell’s internal concentrations of sodium and potassium.
Bloom’s Level: 2. Understanding
a. The exchange pump uses the electrical gradient to pump ions..
b. The exchange pump produces an electrical charge.
c. The exchange pump is responsible for the membrane potential.
d. The exchange pump counteracts the effect of the electrical gradient.
e. The exchange pump uses ions to pump water out of the cell.
Type: multiple choice question
Title: Chapter 06 Question 31
31. Why is the sodium-potassium exchange pump necessary?
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Explain how the sodium–potassium exchange pump maintains a cell’s internal concentrations of sodium and potassium.
Bloom’s Level: 3. Applying
a. To establish a resting membrane potential
b. To counteract the loss of chloride ions from the cell
c. To ensure osmotic balance
d. To keep sodium and potassium flux at a steady state
e. To maintain equal numbers of positive and negative charges across the membrane
Type: multiple choice question
Title: Chapter 06 Question 32
32. Which of the following is true for the sodium-potassium exchange pump?
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Explain how the sodium–potassium exchange pump maintains a cell’s internal concentrations of sodium and potassium.
Bloom’s Level: 2. Understanding
a. It pumps an equal number of ions into and out of the cell.
b. It passively distributes ions along their concentration gradient.
c. It passively distributes ions along their electrical gradient.
d. It pumps two potassium ions into the cell and three sodium ions out of the cell.
e. It is unrelated to maintaining ion balance in the cell.
Type: multiple choice question
Title: Chapter 06 Question 33
33. Values for neuronal resting membrane potentials vary widely, from -90mV to -40mV. This is primarily due to differences in
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Explain how the sodium–potassium exchange pump maintains a cell’s internal concentrations of sodium and potassium.
Bloom’s Level: 5. Evaluating
a. external potassium concentration.
b. external sodium concentration.
c. the sodium-potassium exchange pump.
d. the chloride conductance.
e. the sodium-to-potassium permeability ratio.
Type: multiple choice question
Title: Chapter 06 Question 34
34. What is the approximate maximum value that the sodium-potassium exchange pump can contribute to the resting membrane potential?
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Explain how the sodium–potassium exchange pump maintains a cell’s internal concentrations of sodium and potassium.
Bloom’s Level: 2. Understanding
a. -5 mV
b. -11 mV
c. -24 mV
d. -75 mV
e. -90 mV
Type: multiple choice question
Title: Chapter 06 Question 35
35. The flow of potassium ions out of the cell is countered by which of the following?
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Explain how the sodium–potassium exchange pump maintains a cell’s internal concentrations of sodium and potassium.
Bloom’s Level: 3. Applying
a. An outward flow of chloride ions
b. An inward flow of chloride ions
c. An outward flow of sodium ions
d. An outward flow of calcium ions
e. The sodium-potassium exchange pump
Type: multiple choice question
Title: Chapter 06 Question 36
36. What is the ratio of sodium to potassium exchange for each cycle of the sodium-potassium exchange pump?
Feedback: Subhead: The Resting Membrane Potential
Learning Objective: Explain how the sodium–potassium exchange pump maintains a cell’s internal concentrations of sodium and potassium.
Bloom’s Level: 2. Understanding
a. 1 sodium: 1 potassium
b. 2 sodium: 1 potassium
c. 3 sodium: 2 potassium
d. 2 sodium: 3 potassium
e. 1 sodium: 2 potassium
Type: multiple choice question
Title: Chapter 06 Question 37
37. The action of ion channels to allow current to flow through the membrane can be thought of as which of the following electrical components?
Feedback: Subhead: An Electrical Model of the Membrane
Learning Objective: Describe the electrical properties of the nerve cell membrane.
Bloom’s Level: 3. Applying
a. Capacitor
b. Battery
c. Wires
d. Resistor
e. Voltmeter
Type: multiple choice question
Title: Chapter 06 Question 38
38. The equilibrium potential for an ion can be considered as which of the following electrical components?
Feedback: Subhead: An Electrical Model of the Membrane
Learning Objective: Describe the electrical properties of the nerve cell membrane.
Bloom’s Level: 3. Applying
a. Capacitor
b. Battery
c. Wires
d. Resistor
e. Voltmeter
Type: multiple choice question
Title: Chapter 06 Question 39
39. In the squid axon, potassium contributes approximately how much to the resting membrane potential?
Feedback: Subhead: Predicted Values of Membrane Potential
Learning Objective: Explain why changes in a cell’s external and internal potassium concentrations do not produce the membrane potential changes predicted by the Nernst equation.
Bloom’s Level: 4. Analyzing
a. 15%
b. 30%
c. 45%
d. 60%
e. 75%
Type: multiple choice question
Title: Chapter 06 Question 40
40. In a biological neuron at rest, there is a constant flow of potassium ions out of the cell. This flow is called the
Feedback: Subhead: Predicted Values of Membrane Potential
Learning Objective: Explain what leak currents are and name three types of channels associated with them.
Bloom’s Level: 2. Understanding
a. restive current.
b. sodium-potassium exchange pump current.
c. leak current.
d. electrogenic current.
e. passive current.
Type: multiple choice question
Title: Chapter 06 Question 41
41. What is the most abundant source of potassium to flow out of the cell at the resting membrane potential?
Feedback: Subhead: Predicted Values of Membrane Potential
Learning Objective: Explain what leak currents are and name three types of channels associated with them
Bloom’s Level: 3. Applying
a. The sodium-potassium exchange pump
b. 2P channels
c. M channels
d. The omega current
e. HCN channels
Type: multiple choice question
Title: Chapter 06 Question 42
42. Which of the following is true regarding HCN channels in the neuronal membrane?
Feedback: Subhead: Predicted Values of Membrane Potential
Learning Objective: Explain what leak currents are and name three types of channels associated with them
Bloom’s Level: 3. Applying
a. They are responsible for the bulk of the flow of potassium from the cell at rest.
b. They are voltage-activated at hyperpolarized membrane potentials.
c. They are nonspecific ion channels that allow chloride ions to flow into the cell.
d. They have a 4:1 ratio of potassium to sodium, allowing sodium to flow into the cell.
e. They are blocked by tetrodotoxin.
Type: multiple choice question
Title: Chapter 06 Question 43
43. Whether an increase in chloride permeability is hyperpolarizing or depolarizing depends on
Feedback: Subhead: Predicted Values of Membrane Potential
Learning Objective: Describe the role of chloride channels in controlling the membrane potential.
Bloom’s Level: 4. Analyzing
a. the equilibrium potential for sodium.
b. the relationship between the chloride equilibrium potential and the membrane potential.
c. whether there is active transport of chloride across the membrane.
d. the equilibrium potential for potassium.
e. the neuronal membrane potential.
Type: essay/short answer question
Title: Chapter 06 Question 44
44. Name three conditions that must be met for a cell to remain in a stable condition.
Feedback: The student should have the following three conditions listed: 1) intracellular and extracellular solutions must each be electrically neutral; 2) the cell must be osmotically balanced; 3) there must be no net ionic movement into or out of the cell.
Subhead: A Model Cell
Learning Objective: List the three major requirements for a cell to remain in a stable condition.
Bloom’s Level: 1. Remembering
Type: essay/short answer question
Title: Chapter 06 Question 45
45. Explain what is meant by the equilibrium potential for an ion?
Feedback: The student should explain that the equilibrium potential is the membrane potential (or, the difference in charge between the intracellular and extracellular spaces) where there is no net movement of ions across the membrane; it is the membrane potential that counteracts the diffusion force that is present because of differences in ion concentrations in the intracellular and extracellular spaces.
Subhead: A Model Cell
Learning Objective: List the three major requirements for a cell to remain in a stable condition.
Bloom’s Level: 2. Understanding
Type: essay/short answer question
Title: Chapter 06 Question 46
46. Explain why the charge separation across the cell membrane does not violate the principle of electrical neutrality.
Feedback: The student’s answer should describe that potassium ions that leave the cell collect along the outer membrane surface, leaving the excess anions closely attracted to the inner surface. Both the potassium ions and the counter ions they leave behind are, in effect, removed from the intracellular bulk solution, leaving it neutral.
Subhead: A Model Cell
Learning Objective: Explain why the charge separation across the membrane of a model cell (e.g., one that is permeable only to potassium and chloride) does not violate the principle of electrical neutrality.
Bloom’s Level: 3. Applying
Type: essay/short answer question
Title: Chapter 06 Question 47
47. Why does a neuronal membrane potential change with increases in extracellular potassium concentration, but does not change with an increase in extracellular chloride concentration?
Feedback: The student’s answer should describe that changing the extracellular potassium concentration changes the potassium equilibrium potential, and hence the membrane potential. In contrast, changing extracellular chloride concentration eventually leads to an equivalent change in intracellular chloride, so that the chloride equilibrium potential and the membrane potential are unchanged.
Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 4. Analyzing
Type: essay/short answer question
Title: Chapter 06 Question 48
48. At rest, a cell’s membrane potential is near, but not equal to, the potassium equilibrium potential. Explain why this is the case.
Feedback: The student’s answer should explain that the resting membrane potential is dominated by the potassium equilibrium potential because the membrane is most permeable to potassium at rest. The answer should also note that the resting membrane potential is not equal to the potassium equilibrium potential because of the influence of other ions that are present (for example, sodium) that have a small membrane permeability.
Subhead: The Effect of Extracellular Potassium and Chloride on Membrane Potential
Learning Objective: Explain why the membrane potential is sensitive to changes in extracellular potassium concentration but is relatively unaffected by changes in extracellular chloride concentration.
Bloom’s Level: 4. Analyzing
Type: essay/short answer question
Title: Chapter 06 Question 49
49. Name two features of the squid giant axon that make it particularly suitable for experiments on membrane potentials.
Feedback: The student’s answer should describe that the squid giant axon is large, allowing easy access to the intracellular space, and that it is durable, allowing the axoplasm to be replaced by intracellular perfusate, and for intracellular and extracellular ion concentrations to be controlled.
Subhead: Membrane Potentials in Squid Axons
Learning Objective: Discuss two factors that make the squid giant axon a model system for studying membrane potentials.
Bloom’s Level: 3. Applying
Type: essay/short answer question
Title: Chapter 06 Question 50
50. In retinal ganglion cells, the sodium leak current is relatively large. Explain the effect this has on the resting membrane potential for these cells.
Feedback: The student’s answer should describe that the membrane potential is close to the sum of the sodium and potassium equilibrium potentials multiplied by their conductance; thus, the membrane potential will be influenced by the large sodium current, and that the resulting membrane potential will be relatively depolarized compared to other neurons.
Subhead: Membrane Potentials in Squid Axons
Learning Objective: Explain what the effect of sodium permeability is on membrane potential.
Bloom’s Level: 5. Evaluating
Type: essay/short answer question
Title: Chapter 06 Question 51
51. You are conducting an experiment recording the membrane potential of the squid giant axon. You decide to increase the extracellular concentration of potassium from 10 mM to 30 mM, and then to 200mM. What is the effect on the membrane potential in each case? How do these results compare to the values you would expect from the Nernst equation? Why?
Feedback: The student’s answer should describe that the membrane potential at 30mM external potassium would be fairly close to resting membrane potential, while at 200mM the membrane potential will be more positive. These results are not what would be expected from the Nernst equation because they do not fit a line with a slope of 58, because the membrane is permeable to other ions (most notably sodium), which influence the membrane potential under conditions of low extracellular potassium.
Subhead: Membrane Potentials in Squid Axons
Learning Objective: Explain what the effect of sodium permeability is on membrane potential.
Bloom’s Level: 5. Evaluating
Type: essay/short answer question
Title: Chapter 06 Question 52
52. In 1902, Bernstein postulated that the membrane potential was due to differences in the concentration of Potassium in the intracellular and extracellular fluids. How did Goldman, Hodgkin and Katz refine this relationship to model the membrane potential more exactly?
Feedback: The student’s answer should relate that Goldman, Hodgkin and Katz refined this equation by including the contribution of a sodium leak current, leading to the development of the Goldman-Hodgkin-Katz (or Constant Field) Equation.
Subhead: The Constant Field Equation
Learning Objective: Describe the general principle illustrated by the constant field equation.
Bloom’s Level: 4. Analyzing
Type: essay/short answer question
Title: Chapter 06 Question 53
53. Explain how the actions of the sodium-potassium exchange pump maintains a cell’s internal concentrations of sodium and potassium.
Feedback: The student’s answer should explain that at rest, the membrane is leaky to sodium and potassium ions. In order for the cell to be in steady state, the action of the sodium-potassium exchange pump must offset these leak currents, keeping the concentrations intact.
Subhead: The Resting Membrane Potential
Learning Objective: Explain how the sodium–potassium exchange pump maintains a cell’s internal concentrations of sodium and potassium.
Bloom’s Level: 5. Evaluating
Type: essay/short answer question
Title: Chapter 06 Question 54
54. Describe the following components of the neuron in terms of their electrical properties: The cell membrane, ion equilibrium potentials, ion channels.
Feedback: The student’s answer should list the cell membrane acts as a capacitor to store charge; the equilibrium potentials act as a battery to drive passive current, and the ion channels as resistors that allow ion current to flow.
Subhead: An Electrical Model of the Membrane
Learning Objective: Describe the electrical properties of the nerve cell membrane.
Bloom’s Level: 5. Evaluating
Type: essay/short answer question
Title: Chapter 06 Question 55
55. In modifying the Constant Field Equation, why is it necessary to account for the ratio of potassium to sodium permeability?
Feedback: The student’s answer should explain that the Constant Field Equation assumes zero net current, which is not met in biological neurons; the ratio accounts for the steady-state action of the sodium-potassium exchange pump.
Subhead: Predicted Values of Membrane Potential
Learning Objective: Explain why changes in a cell’s external and internal potassium concentrations do not produce the membrane potential changes predicted by the Nernst equation.
Bloom’s Level 5. Evaluating
Type: essay/short answer question
Title: Chapter 06 Question 56
56. Explain how the sodium–potassium exchange pump contributes to the membrane potential, and how you can predict the magnitude of its effect.
Feedback: The student’s answer should describe the electrogenic nature of the exchange pump (three positive charges pumped out for every two positive charges pumped in, or net charge of -1) and describe how to use the modified constant field equation to determine the net effect of this action on the membrane potential.
Subhead: Predicted Values of Membrane Potential
Learning Objective: Explain how the sodium–potassium exchange pump makes a direct contribution of several millivolts to the membrane potential.
Bloom’s Level: 5. Evaluating
Type: essay/short answer question
Title: Chapter 06 Question 57
57. In your neurology practice, you meet a patient who complains of a temporary inability to move her legs, a condition that lasts for hours to days at a time. What is your diagnosis, including a description of the molecular mechanism that underlies this condition?
Feedback: The student’s answer should identify the condition as hypokalemic periodic paralysis, caused by a mutation in which charge-carrying arginine residues on the sodium channel S4 helix are replaced by smaller neutral amino acids, allowing cations to permeate the pore, and a constant inward leak of sodium into the muscle cell.
Subhead: Predicted Values of Membrane Potential
Learning Objective: Explain what leak currents are and name three types of channels associated with them.
Bloom’s Level 5. Evaluating
Type: essay/short answer question
Title: Chapter 06 Question 58
58. How would an increase in chloride conductance affect the changes in the membrane potential?
Feedback: The student’s answer should explain that increases in chloride conductance will not change the resting membrane potential but will stabilize the membrane potential at a value close to the chloride equilibrium potential.
Subhead: Predicted Values of Membrane Potential
Learning Objective: Describe the role of chloride channels in controlling the membrane potential.
Bloom’s Level: 5. Evaluating