Question 1

What is thought to be the functional significance of charged amino acids along the S4 helix of the voltage-gated sodium channel?

Accepted Answer

A)  They form the basis for sodium selectivity of the channel. 
B)  They provide a mechanism for inactivation. 
C)  They attract the negative charges of nearby channel subunits, forming a functional protein. 
D)  They form the pore of the channel. 
E)  They provide the gating mechanism for channel opening. 
A)  They form the basis for sodium selectivity of the channel. 
B)  They provide a mechanism for inactivation. 
C)  They attract the negative charges of nearby channel subunits, forming a functional protein. 
D)  They form the pore of the channel. 
E)  They provide the gating mechanism for channel opening.

Question 2

An increase in the sodium conductance results in which of the following?

Accepted Answer

A)  A depolarization of the neuronal membrane potential 
B)  A hyperpolarization of the neuronal membrane potential 
C)  A repolarization of the neuronal membrane potential 
D)  An action potential 
E)  An afterhyperpolarizing potential 
A)  A depolarization of the neuronal membrane potential 
B)  A hyperpolarization of the neuronal membrane potential 
C)  A repolarization of the neuronal membrane potential 
D)  An action potential 
E)  An afterhyperpolarizing potential

Question 3

The late current observed in voltage clamp experiments contributes to which of these phases of the action potential?

Accepted Answer

A)  Depolarization 
B)  Inactivation 
C)  Repolarization 
D)  Threshold 
E)  Refractory period 
A)  Depolarization 
B)  Inactivation 
C)  Repolarization 
D)  Threshold 
E)  Refractory period

Question 4

When is a sodium channel most likely to open following a depolarizing stimulus in the neuron?

Accepted Answer

A)  100 milliseconds 
B)  10 milliseconds 
C)  4-6 milliseconds 
D)  1-2 milliseconds 
E)  <1 millisecond 
A)  100 milliseconds 
B)  10 milliseconds 
C)  4-6 milliseconds 
D)  1-2 milliseconds 
E)  <1 millisecond

Question 5

Which of the following is true of sodium and potassium conductances in neurons?

Accepted Answer

A)  They both increase with an increase in the membrane potential. 
B)  They both decrease with an increase in the membrane potential. 
C)  Sodium conductance increases, while potassium conductance decreases, with an increase in the membrane potential. 
D)  Sodium conductance decreases, while potassium conductance increases, with an increase in the membrane potential. 
E)  None of these describe the relationship between ion conductance and membrane potential. 
A)  They both increase with an increase in the membrane potential. 
B)  They both decrease with an increase in the membrane potential. 
C)  Sodium conductance increases, while potassium conductance decreases, with an increase in the membrane potential. 
D)  Sodium conductance decreases, while potassium conductance increases, with an increase in the membrane potential. 
E)  None of these describe the relationship between ion conductance and membrane potential.

Question 6

The early current observed in voltage clamp experiments contributes to which of these phases of the action potential?

Accepted Answer

A)  Depolarization 
B)  Inactivation 
C)  Repolarization 
D)  Threshold 
E)  Refractory period 
A)  Depolarization 
B)  Inactivation 
C)  Repolarization 
D)  Threshold 
E)  Refractory period

Question 7

Which of the following can be attributed to the flow of sodium ions across the membrane?

Accepted Answer

A)  Capacitative current 
B)  Gating current 
C)  Early current 
D)  Late current 
E)  Afterhyperpolarizing potential (AHP) 
A)  Capacitative current 
B)  Gating current 
C)  Early current 
D)  Late current 
E)  Afterhyperpolarizing potential (AHP)

Question 8

In a voltage clamp experiment, you record from a neuron after a command voltage step to -10 mV. In a second experiment, you step the command voltage to +50 mV. What do you notice about the sodium current in the second experiment, compared to the first?

Accepted Answer

A)  The sodium current is larger. 
B)  The sodium current is smaller. 
C)  The sodium current is the same magnitude. 
D)  The sodium current appears earlier in time. 
E)  The sodium current appears later in time. 
A)  The sodium current is larger. 
B)  The sodium current is smaller. 
C)  The sodium current is the same magnitude. 
D)  The sodium current appears earlier in time. 
E)  The sodium current appears later in time.

Question 9

How do changes in sodium and potassium conductance following membrane depolarization lead to an action potential?

Accepted Answer

The student should answer that the first

Question 10

How does extracellular calcium affect neuronal excitability?

Accepted Answer

The student should answer that extracell

Question 11

The transport rate of the sodium-potassium cotransporter increases as

Accepted Answer

A)  intracellular sodium concentration increases. 
B)  extracellular sodium concentration increases. 
C)  intracellular potassium concentration increases. 
D)  extracellular potassium concentration increases. 
E)  the transport rate does not change with ion concentration. 
A)  intracellular sodium concentration increases. 
B)  extracellular sodium concentration increases. 
C)  intracellular potassium concentration increases. 
D)  extracellular potassium concentration increases. 
E)  the transport rate does not change with ion concentration.

Question 12

During the late phase of an action potential, the threshold for activating a subsequent action potential is larger than when the neuron is at rest. This relative refractory period is due to a very large

Accepted Answer

A)  increase in sodium conductance. 
B)  increase in potassium conductance. 
C)  decrease in potassium conductance. 
D)  increase in chloride conductance. 
E)  decrease in calcium conductance. 
A)  increase in sodium conductance. 
B)  increase in potassium conductance. 
C)  decrease in potassium conductance. 
D)  increase in chloride conductance. 
E)  decrease in calcium conductance.

Question 13

Which of the following ions is responsible for the late current following a voltage step in a voltage clamp experiment?

Accepted Answer

A)  Sodium 
B)  Potassium 
C)  Chloride 
D)  Calcium 
E)  Magnesium 
A)  Sodium 
B)  Potassium 
C)  Chloride 
D)  Calcium 
E)  Magnesium

Question 14

Spike frequency adaptation is mediated by a(n)

Accepted Answer

A)  increase in sodium conductance with repeated action potentials. 
B)  decrease in sodium conductance with repeated action potentials. 
C)  increase in potassium conductance with repeated action potentials. 
D)  decrease in potassium conductance with repeated action potentials. 
E)  decrease in the availability of sodium channels with repeated action potentials. 
A)  increase in sodium conductance with repeated action potentials. 
B)  decrease in sodium conductance with repeated action potentials. 
C)  increase in potassium conductance with repeated action potentials. 
D)  decrease in potassium conductance with repeated action potentials. 
E)  decrease in the availability of sodium channels with repeated action potentials.

Question 15

What is frequency adaptation, and what is the mechanism by which it occurs?

Accepted Answer

The student should answer that frequency

Question 16

What is the approximate mean open time for a voltage-gated sodium channel?

Accepted Answer

A)  100 milliseconds 
B)  10 milliseconds 
C)  5 milliseconds 
D)  2 milliseconds 
E)  <1 millisecond 
A)  100 milliseconds 
B)  10 milliseconds 
C)  5 milliseconds 
D)  2 milliseconds 
E)  <1 millisecond

Exam 7: Ionic Basis of the Action Potential

What is thought to be the functional significance of charged amino acids along the S4 helix of the voltage-gated sodium channel?

An increase in the sodium conductance results in which of the following?

The late current observed in voltage clamp experiments contributes to which of these phases of the action potential?

When is a sodium channel most likely to open following a depolarizing stimulus in the neuron?

Which of the following is true of sodium and potassium conductances in neurons?

The early current observed in voltage clamp experiments contributes to which of these phases of the action potential?

Which of the following can be attributed to the flow of sodium ions across the membrane?

In a voltage clamp experiment, you record from a neuron after a command voltage step to -10 mV. In a second experiment, you step the command voltage to +50 mV. What do you notice about the sodium current in the second experiment, compared to the first?

How do changes in sodium and potassium conductance following membrane depolarization lead to an action potential?

How does extracellular calcium affect neuronal excitability?

The transport rate of the sodium-potassium cotransporter increases as

During the late phase of an action potential, the threshold for activating a subsequent action potential is larger than when the neuron is at rest. This relative refractory period is due to a very large

Which of the following ions is responsible for the late current following a voltage step in a voltage clamp experiment?

Spike frequency adaptation is mediated by a(n)

What is frequency adaptation, and what is the mechanism by which it occurs?

What is the approximate mean open time for a voltage-gated sodium channel?

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

Electrical Signaling in Neurons

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

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