Electrical Signaling In Neurons Chapter 8 Complete Test Bank

Chapter 8: Electrical Signaling in Neurons

Test Bank

Type: multiple choice question

Title: Chapter 08 - Question 01

1. How does the size of a cell influence its input capacitance and resistance?

Feedback: Subhead: Specific Electrical Properties of Cell Membranes
Learning Objective: Name the cell properties on which input capacitance and input resistance depend.

Bloom’s Level: 4. Analysis

a. The larger the cell is, the larger its input capacitance and resistance will be.

b. The larger the cell is, the smaller its input capacitance and resistance will be.

c. The input capacitance increases with cell size, whereas the input resistance decreases with cell size.

d. The input capacitance is inversely proportional to cell size, whereas the input resistance is directly proportional to it.

e. The size of the cell does not influence either the input resistance of capacitance, because both values are exclusively determined by the molecular composition of the cell membrane.

Type: multiple choice question

Title: Chapter 08 - Question 02

2. Is the specific membrane resistance (R_m) expressed in Ω cm²?

Feedback: Subhead: Specific Electrical Properties of Cell Membranes
Learning Objective: Name the cell properties on which input capacitance and input resistance depend.

Bloom’s Level: 2. Understanding

a. Yes, because it varies depending on the phospholipid composition of the membrane bilayer.

b. Yes, because it depends on the number of open channels in a given surface area.

c. No, the specific membrane resistance is measured in Ω.

d. No, the specific membrane resistance is measured in Ω/cm².

e. No, because the specific membrane resistance does not vary with cell size.

Type: multiple choice question

Title: Chapter 08 - Question 03

3. Which formula allows you to calculate the membrane time constant τ_m?

Feedback: Subhead: Specific Electrical Properties of Cell Membranes
Learning Objective: Not aligned
Bloom’s Level: 3. Applying

a. τ_m = R_m/4πr²

b. τ_m = ir_input

c. τ_m = C_m V

d. τ_m = R_m C_m

e. τ_m = ΔV_max e^(–t/τ)

Type: multiple choice question

Title: Chapter 08 - Question 04

4. What is the membrane conductance of a cell with a specific membrane resistance of 1,000 Ω cm² and 50,000 Ω cm²?

Feedback: Subhead: Specific Electrical Properties of Cell Membranes
Learning Objective: Not aligned
Bloom’s Level: 4. Analysis

a. The first cell has a specific membrane conductance of 1 × 10⁹ pS/cm², the second cell has a specific membrane conductance of 2 × 10⁹ pS/cm². Therefore, the first cell has a larger surface density of open channels.

b. The first cell has a specific membrane conductance of 1 × 10⁹ pS/cm², the second cell has a specific membrane conductance of 2 × 10⁷ pS/cm². Therefore, the first cell has a smaller surface density of open channels.

c. The first cell has a specific membrane conductance of 100 × 10⁷ pS/cm², the second cell has a specific membrane conductance of 2 × 10⁷ pS/cm². Therefore, the first cell has a larger surface density of open channels.

d. The first cell has a specific membrane conductance of 1 × 10⁷ pS/cm², the second cell has a specific membrane conductance of 0.5 × 10⁷ pS/cm². Therefore, the first cell has a smaller surface density of open channels.

e. The first cell has a specific membrane conductance of 1 × 10⁹ pS/cm², the second cell has a specific membrane conductance of 2 × 10⁷ pS/cm². These values do not depend on the surface density of open channels.

Type: multiple choice question

Title: Chapter 08 - Question 05

5. In cortical neurons, you can identify the following five sub-cellular compartments. If you were to apply a sub-threshold current step of fixed amplitude to each one of them, where would you evoke the smallest change in membrane potential?

Feedback: Subhead: Specific Electrical Properties of Cell Membranes
Learning Objective: Not aligned
Bloom’s Level: 4. Analysis

a. Soma

b. Terminal dendrites

c. Proximal dendrites

d. Axon

e. Axon initial segment

Type: multiple choice question

Title: Chapter 08 - Question 06

6. Why is the effect of injecting a pulse of correct in a dendrite more complex than the one evoked by injecting a pulse of current in a spherical cell?

Feedback: Subhead: Flow of Current in a Nerve Fiber
Learning Objective: Name the two factors that determine the size of the response to current injection of a nerve fiber and how far the signal will spread along the fiber.
Bloom’s Level: 5. Evaluating

a. Because the molecular composition of the dendritic membrane is different from that of a spherical cell, due to the presence of specific types of ion channels.

b. Because it is not possible to study the biophysical properties of small, sub-cellular compartments like dendrites.

c. Because the current injected in a dendrite only flows outward through the cell membrane.

d. Because the cross section of dendrites varies along the length of the dendrite.

e. Because the dendritic compartment cannot be represented by only one RC circuit as the injected current flows along the length of the dendrite and not just across the membrane.

Type: multiple choice question

Title: Chapter 08 - Question 07

7. What relationship describes how the amplitude of a membrane potential change varies with the distance from a current injection site?

Feedback: Subhead: Flow of Current in a Nerve Fiber
Learning Objective: Name the two factors that determine the size of the response to current injection of a nerve fiber and how far the signal will spread along the fiber.
Bloom’s Level: 2. Understanding

a. ΔV = ΔV₀ e^–t/τ

b. ΔV = ΔV₀ e^-x/λ

c. ΔV = ΔV₀ (1 – e^–t/τ)

d. ΔV = ir_input

e. ΔV = Q/C

Type: multiple choice question

Title: Chapter 08 - Question 08

8. How does the membrane resistance affect the membrane length constant?

Feedback: Subhead: Flow of Current in a Nerve Fiber
Learning Objective: Name the two factors that determine the size of the response to current injection of a nerve fiber and how far the signal will spread along the fiber.

Bloom’s Level: 4. Analyzing

a. The membrane length constant increases as the membrane resistance increases.

b. The membrane length constant increases as the membrane resistance decreases.

c. The membrane length constant does not depend on the membrane resistance.

d. The membrane length constant only changes if the resistance of the cytoplasm changes.

e. The membrane length constant cannot be calculated when the membrane resistance changes.

Type: multiple choice question

Title: Chapter 08 - Question 09

9. What is the membrane length constant of a cell with membrane resistance r_m = 1 Ω cm and cytoplasmic resistance r_i = 100 Ω/cm?

Feedback: Subhead: Flow of Current in a Nerve Fiber
Learning Objective: Name the two factors that determine the size of the response to current injection of a nerve fiber and how far the signal will spread along the fiber.

Bloom’s Level: 4. Analyzing

a. λ = 0.1 mm

b. λ = 1 mm

c. λ = 10 mm

d. λ = 1 cm

e. λ = 10 cm

Type: multiple choice question

Title: Chapter 08 - Question 10

10. Does the effect of an inhibitory input change depending on whether it targets a dendritic compartment with a small or large cross section?

Feedback: Subhead: Flow of Current in a Nerve Fiber
Learning Objective: Explain why large processes generally have greater length constants than small processes.

Bloom’s Level: 5. Evaluating

a. Yes, the change in membrane potential caused by the inhibitory input will be larger in dendrites with larger cross-section because the membrane resistance is directly proportional to dendrite diameter.

b. No, the change in membrane potential caused by the inhibitory input will be the same in dendrites with large and small cross-sections, because it is not influenced by the cross section of these processes.

c. Yes, the change in membrane potential caused by the inhibitory input will be larger in dendrites with smaller cross-section because the membrane resistance is inversely proportional to dendrite diameter.

d. No, the change in membrane potential caused by the inhibitory input will be the same in dendrites with large and small cross-sections, because the membrane and cytoplasmic resistance of these compartments is the same.

e. The effect of the inhibitory input depends only on the local density of voltage-gated sodium and potassium channels.

Type: multiple choice question

Title: Chapter 08 - Question 11

11. What is the relation between the membrane capacitance (c_m) and the specific membrane capacitance (C_m)?

Feedback: Subhead: Flow of Current in a Nerve Fiber
Learning Objective: Explain why large processes generally have greater length constants than small processes.

Bloom’s Level: 4. Analyzing

a. c_m = C_m

b. c_m = C_m(πa²)

c. c_m is calculated at 20°C, whereas C_m is calculated at 37°C.

d. c_m is independent on fiber size, whereas C_m varies inversely proportionately to it.

e. c_m = C_m(2πa)

Type: multiple choice question

Title: Chapter 08 - Question 12

12. In mammals, the specific membrane resistance is

Feedback: Subhead: Flow of Current in a Nerve Fiber
Learning Objective: Not aligned
Bloom’s Level: 2. Understanding

a. smaller than in squids, where the intracellular ion concentration is lower.

b. smaller than in frogs, where the intracellular ion concentration is lower.

c. similar to that of other non-mammalian species including squids and frogs.

d. comparable to that of copper.

e. much smaller than copper, making the conduction of electrical signals particularly efficient.

Type: multiple choice question

Title: Chapter 08 - Question 13

13. What is an electrotonic potential?

Feedback: Subhead: Flow of Current in a Nerve Fiber
Learning Objective: Not aligned

Bloom’s Level: 2. Understanding

a. It is a change in membrane potential analogous to that evoked by an action potential.

b. It is a graded potential that relies on the opening of voltage-gated ion channels.

c. It is the potential change at the point of current injection.

d. It is a graded potential that becomes progressively smaller as it spreads along the cell membrane.

e. It is a spontaneous fluctuation in the resting membrane potential of a cell.

Type: multiple choice question

Title: Chapter 08 - Question 14

14. What is the distance occupied by an action potential, if you could freeze it in time, assuming it lasts 1 ms and travels at a speed of 10 m/s?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Name the two factors that determine how far an action potential spreads. Bloom’s Level: 4. Analyzing

a. 10 mm

b. 20 mm

c. 1 mm

d. 2 mm

e. 0.5 mm

Type: multiple choice question

Title: Chapter 08 - Question 15

15. What is the main difference between the α, β, and δ sub-types of vertebrate group A myelinated fibers?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Name the two factors that determine how quickly an action potential spreads.
Bloom’s Level: 3. Applying

a. Size

b. Extent of myelination

c. Action potential conduction velocity

d. Identify of their cellular target

e. Protein composition

Type: multiple choice question

Title: Chapter 08 - Question 16

16. What is the main contributor to the refractory period following the onset of an action potential?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Explain how the refractory period prevents re-excitation from occurring. Bloom’s Level: 2. Understanding

a. Inactivation of voltage-gated sodium channels

b. Closing of voltage-gated sodium channels

c. Opening of leak potassium channels

d. Sodium influx

e. Potassium efflux

Type: multiple choice question

Title: Chapter 08 - Question 17

17. Which cells form myelin sheets in the central nervous system?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Describe what myelin is and what effect it has on nerve fibers.
Bloom’s Level: 1. Remembering

a. Schwann cells

b. Astrocytes

c. Microglia

d. Neurons

e. Oligodendrocytes

Type: multiple choice question

Title: Chapter 08 - Question 18

18. How many lamellae of myelin typically wrap large nerve fibers in the vertebrate nervous system?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Describe what myelin is and what effect it has on nerve fibers.

Bloom’s Level: 1. Remembering

a. 10–20

b. 20–40

c. 140–160

d. 10–160

e. None

Type: multiple choice question

Title: Chapter 08 - Question 19

19. What is the name of the periodic interruptions of myelin sheets along nerve fibers?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Describe what myelin is and what effect it has on nerve fibers.

Bloom’s Level: 1. Remembering

a. Schwann cells

b. Nodes of Ranvier

c. Synapses

d. Hot spots

e. Nerve knots

Type: multiple choice question

Title: Chapter 08 - Question 20

20. What is the main function of M-channels at the node of Ranvier?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Describe what myelin is and what effect it has on nerve fibers.

Bloom’s Level: 3. Applying

a. They prevent ectopic action potential discharges.
b. They promote action potential propagation.

c. They depolarize the membrane potential.

d. They prolong the refractory period.

e. They promote myelination.

Type: multiple choice question

Title: Chapter 08 - Question 21

21. How can you test the hypothesis that demyelination disrupts the confined expression of voltage-gated sodium channels in the node of Ranvier?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Describe what myelin is and what effect it has on nerve fibers.

Bloom’s Level: 6. Creating

a. By analyzing the effect of diphtheria toxin on action potential repolarization

b. By changing the ionic composition of the extracellular solution where the isolated nerve fiber is stored

c. By severing nerve fibers

d. By using pharmacological agents that block KCNQ2-containing M-channels

e. By comparing the sodium channel distribution along myelinated and demyelinated fibers treated with diphtheria toxin

Type: multiple choice question

Title: Chapter 08 - Question 22

22. What is the functional advantage of having few shorter internodes before an unmyelinated nerve terminal?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Describe what myelin is and what effect it has on nerve fibers.

Bloom’s Level: 6. Creating

a. It ensures that action potentials do not invade nerve terminals.

b. It increases the number of branch points and therefore promotes conduction block.

c. It serves to boost local depolarization of nerve terminals and promote neurotransmitter release.

d. It prevents neurons from reaching the threshold for action potentials, preventing hyperactivity.

e. It simplifies the geometry of the nerve ending.

Type: multiple choice question

Title: Chapter 08 - Question 23

23. Which ion channels are highly concentrated in the nodes of Ranvier?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Explain what saltatory conduction is.

Bloom’s Level: 2. Understanding

a. Delayed rectifier potassium channels

b. Sodium channels

c. Calcium channels

d. Leak channels

e. None of the above

Type: multiple choice question

Title: Chapter 08 - Question 24

24. How does the passive spread of current ahead of the active region of a nerve fiber contribute to action potential propagation?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Discuss how fiber size affects the electrical properties of nerves.

Bloom’s Level: 5. Evaluating

a. It provides directionality to the propagation of the action potential.

b. It changes the speed at which the action potential propagates.

c. It causes a new segment of the cell membrane to be depolarized to threshold.

d. It allows the action potential to propagate only along a portion of the nerve fiber.

e. It promotes action potential attenuation.

Type: multiple choice question

Title: Chapter 08 - Question 25

25. Which ion channels are abundant in the paranodal region?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Not aligned

Bloom’s Level: 2. Understanding

a. Voltage gated sodium channels

b. Slowly inactivating potassium channels

c. M-channels

d. Delayed rectifier potassium channels

e. Leak channels

Type: multiple choice question

Title: Chapter 08 - Question 26

26. Which pathological states are known to be associated with genetic mutations that impair the function of the potassium channel subunit KCNQ2?

Feedback: Subhead: Action Potential Propagation
Learning Objective: Not aligned

Bloom’s Level: 1. Remembering

a. Heart arrhythmia

b. Epileptic seizures and myokymia

c. Coma

d. Cerebellar ataxia

e. Parkinson’s disease

Type: multiple choice question

Title: Chapter 08 - Question 27

27. How do branch points affect action potential propagation?

Feedback: Subhead: Geometry and Conduction Block
Learning Objective: Discuss how the geometry of neurons provides possibilities for blocking the propagation of action potentials.

Bloom’s Level: 4. Analyzing

a. They increase the membrane area that is depolarized by the action potential.

b. They increase the local membrane resistance.

c. They promote action potential propagation through higher order branches.

d. They delay action potential propagation.

e. They increase the local values of membrane resistance and capacitance.

Type: multiple choice question

Title: Chapter 08 - Question 28

28. In 1955, J.C. Eccles and colleagues made which fundamental experimental observation regarding cell excitability and action potential generation?

Feedback: Subhead: Conduction in Dendrites
Learning Objective: Discuss how dendritic action potentials differ from somatic action potentials.

Bloom’s Level: 2. Understanding

a. Dendritic depolarization initiates action potentials near the soma, not in the dendrites.

b. Dendrites are generally unexcitable and only transmit signals passively towards the soma.

c. Action potentials travel along dendrites with a conduction velocity of 3 m/s.

d. Cerebellar Purkinje neurons produce dendritic action potentials.

e. Action potentials are initiated in the axon initial segment, and then propagate along the axon and back into the soma and dendrites.

Type: multiple choice question

Title: Chapter 08 - Question 29

29. Modest activation of distal synapses produces a local dendritic depolarization that propagates electrotonically towards the soma and can trigger an action potential at the soma. Stronger activation of distal synapses evokes a dendritic calcium action potential that also results in the generation of a somatic action potential. How can you distinguish these two scenarios using dual somatic and dendritic recordings?

Feedback: Subhead: Conduction in Dendrites
Learning Objective: Discuss how dendritic action potentials differ from somatic action potentials.

Bloom’s Level: 6. Creating

a. With modest stimuli, the action potential recorded from the soma precedes the one recorded from the dendrite. With stronger stimuli, the action potential recorded from the soma follows the one recorded from the dendrite. In addition, in this case, the two action potentials display a shorter latency.

b. With modest stimuli, the action potential recorded from the soma is smaller than the one recorded from the dendrite. With stronger stimuli, the action potential recorded from the soma is larger than the one recorded from the dendrite.

c. With modest stimuli, the action potential recorded from the soma is longer than the one recorded from the dendrite. With stronger stimuli, the action potential recorded from the soma is shorter than the one recorded from the dendrite.

d. With modest stimuli, there is typically no action potential recorded from the soma. With stronger stimuli, the action potential recorded from the dendrite shows an after-depolarization, which cannot be detected from the soma.

e. The two recordings are indistinguishable using these experimental configurations.

Type: multiple choice question

Title: Chapter 08 - Question 30

30. Which factors make propagation of electrical signals in dendrites more complex than in axons?

Feedback: Subhead: Conduction in Dendrites
Learning Objective: Discuss how dendritic action potentials differ from somatic action potentials.

Bloom’s Level: 4. Analyzing

a. The membrane capacitance of dendrites differs from that of neurons.

b. Dendrites do not express voltage-gated ion channels.

c. Dendrites contain a wide variety of voltage-gated ion channels and different branches have different input resistance, which varies with the activity of excitatory and inhibitory synapses.

d. Dendrites do not receive excitatory and inhibitory synaptic inputs.

e. Dendrites typically have smaller input resistance than axons, which prevents efficient propagation of electrical signals.

Type: multiple choice question

Title: Chapter 08 - Question 31

31. What type of active signals can you record by delivering supra-threshold current injections to dendrites located away from the soma of cerebella Purkinje neurons?

Feedback: Subhead: Conduction in Dendrites
Learning Objective: Discuss how dendritic action potentials differ from somatic action potentials.

Bloom’s Level: 3. Applying

a. Fast sodium action potentials

b. Fast hyperpolarizing potentials

c. Action potentials propagating passively from the soma

d. Long-duration calcium action potentials

e. None, because no action potential makes it to dendrites away from the axon initial segment

Type: multiple choice question

Title: Chapter 08 - Question 32

32. Which of the following cells does not exhibit electrical coupling?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Explain what electrical coupling is and list three types of cell in which it occurs.

Bloom’s Level: 1. Remembering

a. Cardiac cells

b. Smooth muscle cells

c. Epithelial cells

d. Gland cells

e. Purkinje cells

Type: multiple choice question

Title: Chapter 08 - Question 33

33. What structures ensure electrical coupling among cells?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Explain what electrical coupling is and list three types of cell in which it occurs.

Bloom’s Level: 2. Understanding

a. Synapses

b. Gap junctions

c. Dendrites

d. Axons

e. Neurons

Type: multiple choice question

Title: Chapter 08 - Question 34

34. What is a connexon?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Describe the structure and function of connexons.

Bloom’s Level: 1. Remembering

a. It is the name of each of the six proteins forming the pore of a gap junction.

b. It is the portion of the extracellular space through which currents flow.

c. It is an intracellular structure coupling adjacent organelles.

d. It is an assembly of six proteins forming the pore of a gap junction.

e. It is the name of the non-pore-forming portion of an electrical junction.

Type: multiple choice question

Title: Chapter 08 - Question 35

35. How many subunits (connexins) does a connexon have?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Describe the structure and function of connexons.
Bloom’s Level: 5. Evaluating

a. 6

b. 5

c. 4

d. 3

e. 2

Type: multiple choice question

Title: Chapter 08 - Question 36

36. What is the typical diameter of a connexon?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Describe the structure and function of connexons.

Bloom’s Level: 1. Remembering

a. 100 nm

b. 1 nm

c. 10 nm

d. 1 μm

e. 10 μm

Type: multiple choice question

Title: Chapter 08 - Question 37

37. A connexon assembled from more than one type of connexins is called

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Describe the structure and function of connexons.

Bloom’s Level: 4. Analyzing

a. homomeric.

b. heteromeric.

c. heterotypic.

d. homotipice.

e. heteroconnexon.

Type: multiple choice question

Title: Chapter 08 - Question 38

38. Which type of connexons have high permeability to ATP and glutamate?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Describe the structure and function of connexons.

Bloom’s Level: 2. Understanding

a. Cx32

b. Cx36

c. Cx40

d. Cx26

e. Cx43

Type: multiple choice question

Title: Chapter 08 - Question 39

39. What is the size of the largest molecular than can pass through the pore of gap junctions?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Explain what gap junctions are.

Bloom’s Level: 2. Understanding

a. 1 KDa

b. 100 Da

c. 10 Da

d. 1 Da

e. Gap junctions are only permeable to ions

Type: multiple choice question

Title: Chapter 08 - Question 40

40. How do even the lowest single-channel conductance gap junctions provide a significant path for current flow between cells?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Explain what gap junctions are.

Bloom’s Level: 4. Analyzing

a. Their single-channel conductance can be modified by neuronal activity.

b. There is a large driving force that favors ion movement across gap junctions.

c. They are typically expressed at a local high density.

d. Ions lose their hydration shell as they pass through the pore of gap junctions.

e. Even the lowest single-channel conductance gap junction forms a very wide pore for the movement of ions across the membrane.

Type: multiple choice question

Title: Chapter 08 - Question 41

41. Which features does not allow you to identify gap junctions between two neuronal processes in electron microscopy images?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Explain what gap junctions are.

Bloom’s Level: 5. Evaluating

a. There is no synaptic vesicle on either side of the junction.

b. The space between the two membranes is narrower than outside of the gap junction.

c. There is an electron-dense thick region on both sides of the membrane.

d. The connexins of each connexon are readily visible with electron microscopy resolution.

e. The gap junction can be formed between two dendrites.

Type: multiple choice question

Title: Chapter 08 - Question 42

42. How many transmembrane helices does each connexin have?

Feedback: Subhead: Pathways for Current Flow between Cells
Learning Objective: Not aligned

Bloom’s Level: 2. Understanding

a. 3

b. 4

c. 6

d. 7

e. None

Type: essay/short answer question

Title: Chapter 08 - Question 43

43. What are the input resistance and capacitance?

Feedback: The input resistance is the resistance that the cell membrane offers to current flow. The input capacitance is the electrical equivalent of the charged layers on the extracellular and intracellular surfaces of the lipid membrane, determined by the electrical insulating properties and thickness of the membrane lipid. The input capacitance is directly proportional to the cell’s surface area.
Subhead: Specific Electrical Properties of Cell Membranes
Learning Objective: Name the cell properties on which input capacitance and input resistance depend.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 08 - Question 44

44. What are the specific membrane resistance and capacitance?

Feedback: The specific membrane capacitance is the capacitance of 1 square centimeter of membrane. The specific resistance of the membrane is the resistance of 1 square centimeter of membrane.
Subhead: Specific Electrical Properties of Cell Membranes
Learning Objective: Name the cell properties on which input capacitance and input resistance depend.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 08 - Question 45

45. What is the equivalent electrical circuit of a cell?

Feedback: It is an RC circuit, with input resistance and capacitance connected in parallel.
Subhead: Specific Electrical Properties of Cell Membranes
Learning Objective: Not aligned

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 08 - Question 46

46. How do the membrane length and time constant affect the electrotonic propagation of sub-threshold changes in membrane potential?

Feedback: The higher the membrane length constant, the greater the portion of the injected current that spreads at a given distance from the injection site before escaping to the external solution. The higher the membrane time constant, the greater the portion of the injected current that spreads at a given time from the injection site before escaping to the external solution. Therefore, these parameters determine how far and for how long a sub-threshold change in membrane potential travels along the membrane of a nerve fiber.
Subhead: Flow of Current in a Nerve Fiber
Learning Objective: Name the two factors that determine the size of the response to current injection of a nerve fiber and how far the signal will spread along the fiber.

Bloom’s Level: 4. Analyzing

Type: essay/short answer question

Title: Chapter 08 - Question 47

47. Why do action potentials propagate along a preferred direction?

Feedback: Because the peak depolarization of the action potential is followed by a refractory period due to local inactivation of voltage-gated sodium channels, during which re-excitation cannot occur.
Subhead: Action Potential Propagation
Learning Objective: Explain how the refractory period prevents re-excitation from occurring. Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 08 - Question 48

48. How does the distribution of ion channels vary along the length of myelinated fibers?

Feedback: Voltage-gated sodium channels are confined to nodes of Ranvier. Instead, delayed rectifier potassium channels are confined to the paranodal region.
Subhead: Action Potential Propagation
Learning Objective: Describe what myelin is and what effect it has on nerve fibers.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 08 - Question 49

49. Which experiments would you perform to test the hypothesis that there is a heterogeneous distribution of ion channels in myelinated fibers?

Feedback: You could perform voltage clamp experiments from myelinated nerve fibers before and after loosening the myelin sheet, to compare the profile of currents recorded in the node and paranodal regions before and after this treatment. The spatial distribution of different types of ion channels can also be analyzed using an immuno-labelling approach.
Subhead: Subhead: Action Potential Propagation
Learning Objective: Describe what myelin is and what effect it has on nerve fibers.

Bloom’s Level: 6. Creating

Type: essay/short answer question

Title: Chapter 08 - Question 50

50. What does the term “saltatory conduction” refer to?

Feedback: It refers to the ability of excitation to jump from node to node along the length of a myelinated nerve fiber.
Subhead: Action Potential Propagation
Learning Objective: Explain what saltatory conduction is.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 08 - Question 51

51. Which structural features of neurons contribute to action potential conduction block?

Feedback: Branching points.
Subhead: Geometry and Conduction Block
Learning Objective: Discuss how the geometry of neurons provides possibilities for blocking the propagation of action potentials.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 08 - Question 52

52. What experimental findings supported the notion that action potentials arise from the axon initial segment?

Feedback: The experiments of J.C. Eccles and colleagues showed that upon depolarization action potentials were initiated first in the axon hillock, where the initial segment of the axon joins the cell body, and then propagated both outward along the axon and back into the soma and dendrites of the cell. The experiments of Kuffler and Eyzaguirre showed that depolarization of the dendrites in the crayfish stretch receptor initiated action potentials in or near the cell body, rather than in the dendrites themselves.
Subhead: Conduction in Dendrites
Learning Objective: Discuss how dendritic action potentials differ from somatic action potentials.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 08 - Question 53

53. How do action potentials back-propagate along dendrites?

Feedback: The depolarization produced by the initiation of an action potential at the axon initial segment can propagate passively and actively through dendrites, where there can be voltage-gated sodium and calcium channels.
Subhead: Conduction in Dendrites
Learning Objective: Discuss how dendritic action potentials differ from somatic action potentials.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 08 - Question 54

54. How do dendritic excitatory and inhibitory synaptic inputs affect back-propagating action potentials?

Feedback: By changing the membrane potential and input resistance of dendrites.
Subhead: Conduction in Dendrites
Learning Objective: Discuss how dendritic action potentials differ from somatic action potentials.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 08 - Question 55

55. What are the functional benefits of having electrical coupling among cells?

Feedback: Electrical coupling promotes cell synchronization, equalizes voltage differences between coupled cells and, depending on the connexon identity, it promotes sharing energy substrates like ATP among cells.
Subhead: Pathways for Current Flow between Cells
Learning Objective: Explain what gap junctions are.

Bloom’s Level: 4. Analyzing

Type: essay/short answer question

Title: Chapter 08 - Question 56

56. How do different types of connexons differ from one another?

Feedback: Connexons are typically classified based on their molecular weight.
Subhead: Pathways for Current Flow between Cells
Learning Objective: Describe the structure and function of connexons.

Bloom’s Level: 1. Remembering

Type: essay/short answer question

Title: Chapter 08 - Question 57

57. How does the single-channel conductance and local density of connexons affect electrical coupling among cells?

Feedback: The smaller is the single-channel conductance and the density of connexons, the less electrically coupled are two cells.
Subhead: Pathways for Current Flow between Cells
Learning Objective: Describe the structure and function of connexons.

Bloom’s Level: 3. Applying