Question 1

In a voltage clamp experiment, this current is observed immediately after a voltage step and lasts approximately 20 microseconds or less.

Accepted Answer

A)  Capacitative current 
B)  Leak current 
C)  Sodium current 
D)  Potassium current 
E)  Calcium current 
A)  Capacitative current 
B)  Leak current 
C)  Sodium current 
D)  Potassium current 
E)  Calcium current A

Question 2

Following the application of a depolarizing stimulus, which of the following occurs first in a neuron?

Accepted Answer

A)  Afterdepolarizing potential 
B)  Afterhyperpolarizing potential 
C)  Activation of sodium channels 
D)  Activation of potassium channels 
E)  Inactivation of sodium channels 
A)  Afterdepolarizing potential 
B)  Afterhyperpolarizing potential 
C)  Activation of sodium channels 
D)  Activation of potassium channels 
E)  Inactivation of sodium channels C

Question 3

Which of the following is thought to play a role in the inactivation of potassium channels?

Accepted Answer

A)  Charged residues on the S4 helix 
B)  An inactivation gate between domains III and IV 
C)  A "ball" on the N-terminus of each of the channel subunits 
D)  A group of negatively-charged amino acids along the C-terminus 
E)  A short loop between the S4 and S5 helices 
A)  Charged residues on the S4 helix 
B)  An inactivation gate between domains III and IV 
C)  A "ball" on the N-terminus of each of the channel subunits 
D)  A group of negatively-charged amino acids along the C-terminus 
E)  A short loop between the S4 and S5 helices C

Question 4

By subtracting the potassium current from the total ion current in their experiments, Hodgkin and Huxley were able to determine the

Accepted Answer

A)  magnitude of the calcium current. 
B)  duration of the calcium current. 
C)  magnitude of the sodium current. 
D)  magnitude and duration of the sodium current. 
E)  contribution of potassium to the resting membrane potential. 
A)  magnitude of the calcium current. 
B)  duration of the calcium current. 
C)  magnitude of the sodium current. 
D)  magnitude and duration of the sodium current. 
E)  contribution of potassium to the resting membrane potential.

Question 5

By calculating the ionic conductances in the neuronal membrane, Hodgkin and Huxley were able to

Accepted Answer

A)  describe the time course of the action potential. 
B)  predict the molecular makeup of the voltage-gated ion channels. 
C)  explain the basis of the refractory period. 
D)  explain the threshold membrane potential. 
E)  do all of the above. 
A)  describe the time course of the action potential. 
B)  predict the molecular makeup of the voltage-gated ion channels. 
C)  explain the basis of the refractory period. 
D)  explain the threshold membrane potential. 
E)  do all of the above.

Question 6

When Hodgkin and Huxley recorded from a neuron under voltage clamp at +52 mV, which of the following describes what they observed?

Accepted Answer

A)  An inward early current followed by an outward late current 
B)  No early current and an outward late current 
C)  An outward early current followed by an inward late current 
D)  An outward early current followed by an outward late current 
E)  An inward early current followed by no late current 
A)  An inward early current followed by an outward late current 
B)  No early current and an outward late current 
C)  An outward early current followed by an inward late current 
D)  An outward early current followed by an outward late current 
E)  An inward early current followed by no late current

Question 7

What is the molecular mechanism responsible for potassium channel inactivation? Support your answer with experimental evidence.

Accepted Answer

The student's answer should describe the

Question 8

Hodgkin and Huxley found a delayed potassium conductance that occurred following membrane depolarization but not hyperpolarization. For this reason, this conductance was called the

Accepted Answer

A)  depolarizing conductance. 
B)  rightward shift. 
C)  s-curve. 
D)  onward conductance. 
E)  delayed rectifier. 
A)  depolarizing conductance. 
B)  rightward shift. 
C)  s-curve. 
D)  onward conductance. 
E)  delayed rectifier.

Question 9

Both the afterhyperpolarizing current (AHP) and the afterdepolarizing current (ADP) depend on calcium levels altering

Accepted Answer

A)  sodium conductance. 
B)  potassium conductance. 
C)  chloride conductance. 
D)  calcium conductance. 
E)  magnesium conductance. 
A)  sodium conductance. 
B)  potassium conductance. 
C)  chloride conductance. 
D)  calcium conductance. 
E)  magnesium conductance.

Question 10

In an experiment, Hodgkin and Huxley demonstrated that a hyperpolarizing prepulse potential increased sodium conductance by up to 70%, but a depolarizing prepulse potential decreased sodium conductance, with a depolarization to -25 mV resulting in virtually zero sodium conductance. What does this experiment demonstrate?

Accepted Answer

The student should answer that this expe

Question 11

Which of the following is true regarding the role of calcium on action potentials?

Accepted Answer

A)  The magnitude of the action potential depends on calcium concentration. 
B)  Extracellular calcium concentrations set the time constant for action potential decay. 
C)  The falling phase of the action potential is calcium-dependent in some cells. 
D)  The afterhyperpolarizing potential is shorter with increased extracellular calcium. 
E)  The rising phase of the action potential is calcium-dependent in some cells. 
A)  The magnitude of the action potential depends on calcium concentration. 
B)  Extracellular calcium concentrations set the time constant for action potential decay. 
C)  The falling phase of the action potential is calcium-dependent in some cells. 
D)  The afterhyperpolarizing potential is shorter with increased extracellular calcium. 
E)  The rising phase of the action potential is calcium-dependent in some cells.

Question 12

The time constant for the decay of whole-cell sodium current is different than the time course of single sodium channel inactivation. Why?

Accepted Answer

A)  The sodium current depends on the probability of sodium channel activation. 
B)  The time course for sodium channel inactivation is longer than the sodium current. 
C)  The sodium current decays more slowly because of leak channels. 
D)  The sodium current decay depends on the time course of sodium channel inactivation. 
E)  The sodium current decays more rapidly as more sodium channels inactivate. 
A)  The sodium current depends on the probability of sodium channel activation. 
B)  The time course for sodium channel inactivation is longer than the sodium current. 
C)  The sodium current decays more slowly because of leak channels. 
D)  The sodium current decay depends on the time course of sodium channel inactivation. 
E)  The sodium current decays more rapidly as more sodium channels inactivate.

Question 13

Hodgkin and Huxley found that the delayed potassium conductance could be described mathematically by the product of four exponential equations. This suggests that

Accepted Answer

A)  there are four potassium channels present in the neuron. 
B)  the opening of potassium channels depends on four independent events. 
C)  the potassium channel is made up of a single monomeric protein. 
D)  the potassium current will increase exponentially with membrane potential. 
E)  the opening of potassium channels is delayed. 
A)  there are four potassium channels present in the neuron. 
B)  the opening of potassium channels depends on four independent events. 
C)  the potassium channel is made up of a single monomeric protein. 
D)  the potassium current will increase exponentially with membrane potential. 
E)  the opening of potassium channels is delayed.

Question 14

Briefly, explain the significance of Hodgkin and Huxley's finding that the time-course of potassium conductance could be modelled mathematically by an exponential function raised to the 4th power.

Accepted Answer

The student should answer that this resu

Question 15

A neuron bathed in a fluid containing Saxitoxin (STX) is held a in a voltage clamp experiment and the command voltage is stepped to -15 mV. Which of the following currents is observed?

Accepted Answer

A)  Outward sodium current 
B)  Inward sodium current 
C)  Outward potassium current 
D)  Inward potassium current 
E)  No currents are observed 
A)  Outward sodium current 
B)  Inward sodium current 
C)  Outward potassium current 
D)  Inward potassium current 
E)  No currents are observed

Question 16

When triethanolamine (TEA) is applied to a neuron in a voltage clamp experiment, what results are observed?

Accepted Answer

A)  An inward early current followed by an outward late current 
B)  No early current and an outward late current 
C)  An outward early current followed by an inward late current 
D)  An outward early current followed by an outward late current 
E)  An inward early current followed by no late current 
A)  An inward early current followed by an outward late current 
B)  No early current and an outward late current 
C)  An outward early current followed by an inward late current 
D)  An outward early current followed by an outward late current 
E)  An inward early current followed by no late current

Question 17

How does a voltage clamp work?

Accepted Answer

A)  It measures the voltage of a neuron that is placed in the preparation. 
B)  It changes the membrane potential of a neuron using two extracellular electrodes. 
C)  It holds the current across a neuronal membrane constant and measures the changes in voltage. 
D)  It holds the voltage of a neuron constant by injecting current equal to the ionic current passing across the cell membrane. 
E)  It inactivates ion channels so that the only current passing into the cell is delivered by the equipment. 
A)  It measures the voltage of a neuron that is placed in the preparation. 
B)  It changes the membrane potential of a neuron using two extracellular electrodes. 
C)  It holds the current across a neuronal membrane constant and measures the changes in voltage. 
D)  It holds the voltage of a neuron constant by injecting current equal to the ionic current passing across the cell membrane. 
E)  It inactivates ion channels so that the only current passing into the cell is delivered by the equipment.

Question 18

Briefly describe the voltage clamp experimental setup and how it works.

Accepted Answer

The student should explain the experimen

Question 19

What is the role of Calcium-dependent potassium channels in action potential dynamics?

Accepted Answer

A)  They allow potassium to leave the cell during the falling phase of the action potential. 
B)  They allow potassium to enter the cell during the falling phase of the action potential. 
C)  They decrease potassium conductance, causing a return to the resting potential. 
D)  They increase potassium conductance, causing a slow afterhyperpolarizing potential. 
E)  They decrease the length of the relative refractory period following an action potential. 
A)  They allow potassium to leave the cell during the falling phase of the action potential. 
B)  They allow potassium to enter the cell during the falling phase of the action potential. 
C)  They decrease potassium conductance, causing a return to the resting potential. 
D)  They increase potassium conductance, causing a slow afterhyperpolarizing potential. 
E)  They decrease the length of the relative refractory period following an action potential.

Question 20

Which of the following ion conductances is responsible for the afterhyperpolarizing potential?

Accepted Answer

A)  Sodium conductance 
B)  Potassium conductance 
C)  Chloride conductance 
D)  Cadmium conductance 
E)  Magnesium conductance 
A)  Sodium conductance 
B)  Potassium conductance 
C)  Chloride conductance 
D)  Cadmium conductance 
E)  Magnesium conductance

Exam 7: Ionic Basis of the Action Potential

In a voltage clamp experiment, this current is observed immediately after a voltage step and lasts approximately 20 microseconds or less.

Following the application of a depolarizing stimulus, which of the following occurs first in a neuron?

Which of the following is thought to play a role in the inactivation of potassium channels?

By subtracting the potassium current from the total ion current in their experiments, Hodgkin and Huxley were able to determine the

By calculating the ionic conductances in the neuronal membrane, Hodgkin and Huxley were able to

When Hodgkin and Huxley recorded from a neuron under voltage clamp at +52 mV, which of the following describes what they observed?

What is the molecular mechanism responsible for potassium channel inactivation? Support your answer with experimental evidence.

Hodgkin and Huxley found a delayed potassium conductance that occurred following membrane depolarization but not hyperpolarization. For this reason, this conductance was called the

Both the afterhyperpolarizing current (AHP) and the afterdepolarizing current (ADP) depend on calcium levels altering

Which of the following is true regarding the role of calcium on action potentials?

The time constant for the decay of whole-cell sodium current is different than the time course of single sodium channel inactivation. Why?

Hodgkin and Huxley found that the delayed potassium conductance could be described mathematically by the product of four exponential equations. This suggests that

Briefly, explain the significance of Hodgkin and Huxley's finding that the time-course of potassium conductance could be modelled mathematically by an exponential function raised to the 4th power.

A neuron bathed in a fluid containing Saxitoxin (STX) is held a in a voltage clamp experiment and the command voltage is stepped to -15 mV. Which of the following currents is observed?

When triethanolamine (TEA) is applied to a neuron in a voltage clamp experiment, what results are observed?

How does a voltage clamp work?

Briefly describe the voltage clamp experimental setup and how it works.

What is the role of Calcium-dependent potassium channels in action potential dynamics?

Which of the following ion conductances is responsible for the afterhyperpolarizing potential?

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

Filters

Briefly, explain the significance of Hodgkin and Huxley's finding that the time-course of potassium conductance could be modelled mathematically by an exponential function raised to the 4^th power.