Question 1

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

Accepted Answer

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. 
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. E

Question 2

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

Accepted Answer

Voltage-gated sodium channels are confined to nodes of Ranvier. Instead, delayed rectifier potassium channels are confined to the paranodal region.

Question 3

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

Accepted Answer

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.

Question 4

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

Accepted Answer

A)  1 KDa 
B)  100 Da 
C)  10 Da 
D)  1 Da 
E)  Gap junctions are only permeable to ions 
A)  1 KDa 
B)  100 Da 
C)  10 Da 
D)  1 Da 
E)  Gap junctions are only permeable to ions

Question 5

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

Accepted Answer

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. 
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.

Question 6

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

Accepted Answer

A)  10-20 
B)  20-40 
C)  140-160 
D)  10-160 
E)  None 
A)  10-20 
B)  20-40 
C)  140-160 
D)  10-160 
E)  None

Question 7

How do branch points affect action potential propagation?

Accepted Answer

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. 
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.

Question 8

What is the membrane length constant of a cell with membrane resistance rm = 1 F1F1F1S1F1F1F10 cm and cytoplasmic resistance ri = 100 F1F1F1S1F1F1F10/cm?

Accepted Answer

A)  λ = 0.1 mm 
B)  λ = 1 mm 
C)  λ = 10 mm 
D)  λ = 1 cm 
E)  λ = 10 cm 
A)  λ = 0.1 mm 
B)  λ = 1 mm 
C)  λ = 10 mm 
D)  λ = 1 cm 
E)  λ = 10 cm

Question 9

How many subunits (connexins) does a connexon have?

Accepted Answer

A)  6 
B)  5 
C)  4 
D)  3 
E)  2 
A)  6 
B)  5 
C)  4 
D)  3 
E)  2

Question 10

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

Accepted Answer

A)  Delayed rectifier potassium channels 
B)  Sodium channels 
C)  Calcium channels 
D)  Leak channels 
E)  None of the above 
A)  Delayed rectifier potassium channels 
B)  Sodium channels 
C)  Calcium channels 
D)  Leak channels 
E)  None of the above

Question 11

What are the specific membrane resistance and capacitance?

Accepted Answer

The specific membrane capacita

Question 12

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

Accepted Answer

Electrical coupling promotes cell synchr

Question 13

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

Accepted Answer

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. 
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.

Question 14

Which formula allows you to calculate the membrane time constant F1F1F1S1F1F1F10m?

Accepted Answer

A)  F1F1F1S1F1F1F10m = Rm/4F1F1F1S1F1F1F10r2 
B)  F1F1F1S1F1F1F10m = irinput 
C)  F1F1F1S1F1F1F10m = Cm V 
D)  F1F1F1S1F1F1F10m = Rm Cm 
E)  F1F1F1S1F1F1F10m = ΔVmax e(-t/τ) 
A)  F1F1F1S1F1F1F10m = Rm/4F1F1F1S1F1F1F10r2 
B)  F1F1F1S1F1F1F10m = irinput 
C)  F1F1F1S1F1F1F10m = Cm V 
D)  F1F1F1S1F1F1F10m = Rm Cm 
E)  F1F1F1S1F1F1F10m = ΔVmax e(-t/τ)

Question 15

What structures ensure electrical coupling among cells?

Accepted Answer

A)  Synapses 
B)  Gap junctions 
C)  Dendrites 
D)  Axons 
E)  Neurons 
A)  Synapses 
B)  Gap junctions 
C)  Dendrites 
D)  Axons 
E)  Neurons

Question 16

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?

Accepted Answer

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. 
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.

Question 17

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

Accepted Answer

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 
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

Question 18

What is the typical diameter of a connexon?

Accepted Answer

A)  100 nm 
B)  1 nm 
C)  10 nm 
D)  1 F1F1F1S1F1F1F10m 
E)  10 F1F1F1S1F1F1F10m 
A)  100 nm 
B)  1 nm 
C)  10 nm 
D)  1 F1F1F1S1F1F1F10m 
E)  10 F1F1F1S1F1F1F10m

Question 19

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

Accepted Answer

By changing the memb

Question 20

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

Accepted Answer

A)  Size 
B)  Extent of myelination 
C)  Action potential conduction velocity 
D)  Identify of their cellular target 
E)  Protein composition 
A)  Size 
B)  Extent of myelination 
C)  Action potential conduction velocity 
D)  Identify of their cellular target 
E)  Protein composition

Exam 8: Electrical Signaling in Neurons

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

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

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

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

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

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

How do branch points affect action potential propagation?

What is the membrane length constant of a cell with membrane resistance rm = 1  cm and cytoplasmic resistance ri = 100 /cm?

How many subunits (connexins) does a connexon have?

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

What are the specific membrane resistance and capacitance?

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

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

Which formula allows you to calculate the membrane time constant m?

What structures ensure electrical coupling among cells?

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

What is the typical diameter of a connexon?

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

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

Principles of Signaling and Organization

Signaling in the Visual System

Functional Architecture of the Visual Cortex

Ion Channels and Signaling

Structure of Ion Channels

Ionic Basis of the Resting Potential

Ionic Basis of the Action Potential

Ion Transport Across Cell Membranes

Properties and Functions of Neuroglial Cells

Mechanisms of Direct Synaptic Transmission

Indirect Mechanisms of Synaptic Transmission

Release of Neurotransmitters

Neurotransmitters in the Central Nervous System

Transmitter Synthesis, Storage, Transport, and Inactivation

Synaptic Plasticity

The Molecular and Cellular Biology of Synaptic Plasticity

Mechanisms of Extrasynaptic Communication

Autonomic Nervous System

Walking, Flying, and Swimming: Cellular Mechanisms of Sensorimotor Behavior in Invertebrates

Sensory Transduction

Transduction and Transmission in the Retina

Touch, Pain, and Texture Sensation

Auditory and Vestibular Sensation

Constructing Perception

Initiation and Control of Coordinated Muscular Movements

Development of the Nervous System

Critical Periods in Sensory Systems

Regeneration and Repair of Synaptic Connections After Injury

Appendix

Filters

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

Which formula allows you to calculate the membrane time constant _m?