Question 1

The inability of neurons to generate only a part of an action potential is called

Accepted Answer

A)  Latency 
B)  Refractory period 
C)  Stimulus-latency relation 
D)  Excitability 
E)  All-or-none law E

Question 2

Closing of the K+ at the end of the action potential requires

Accepted Answer

A)  Repolarization 
B)  K+ current 
C)  Time 
D)  Depolarization 
E)  Both repolarization and time E

Question 3

The Em for a cell is -70 mV and ECl is -80 mV. Increasing gCl should increase

Accepted Answer

A)  The driving force for Cl- 
B)  Outward flux of Cl- and an inward current to depolarize the cell 
C)  Inward flux of Cl- and an outw ard current that hyperpolarizes the cell 
D)  Inward flux of Cl- and an inward current to depolarize the cell 
E)  Outward flux of Cl- and an outward current to hyperpolarize the cell C

Question 4

The “overshoot” of the action potential means

Accepted Answer

A)  The membrane potential mom entarily becomes m ore negative than EK 
B)  The membrane potential mom entarily becomes more positive than ENa 
C)  Em momentarily becomes positive 
D)  Em becomes m ore positive than ECl 
E)  For a brief moment Em is not described by the chord conductance equation

Question 5

Depolarization refers to

Accepted Answer

A)  Making the membrane potential more negative 
B)  Rotation of the cell counterclockwise about the its axis 
C)  Exciting a cell to make an action potential 
D)  Making the membrane potential less polarized - typically making it less negative 
E)  Increasing the conductance to K+

Question 6

The first step in the nerve action potential from rest is

Accepted Answer

A)  Opening of the fast Na+ activation gates 
B)  Opening of the fast Na+ inactivation gates 
C)  Closing of the K+ activation gates 
D)  Opening of the K+ activation gates 
E)  Hyperpolarization of the membrane

Question 7

Suppose that after an action potential we clam p the membrane potential at -50 mV and don’t let it completely repolarize. We find that we cannot elicit an action potential. This is called a depolarization block. What causes it?

Accepted Answer

A)  Persistently elevated gK 
B)  The inactivation gates do not re-open 
C)  The activation gates of the Na channel are closed 
D)  Persistently elevated gNa 
E)  The inactivation gates are stuck open

Question 8

The time after an excitation during which the cell cannot produce another action potential is called the

Accepted Answer

A)  Latency 
B)  Overshoot 
C)  Relative refractory period 
D)  Absolute refractory period 
E)  Voltage blockade

Question 9

“Latency” refers to the

Accepted Answer

A)  Delay between increase in gNa and gK during the action potential 
B)  Increase in refractoriness imm ediately following the action potential 
C)  Decay in refractory period with excitation 
D)  Prolongation of refractory period with repetitive excitation 
E)  Delay between stimulus and action potential initiation

Question 10

Opening of the inactivation gate of the Na channel

Accepted Answer

A)  Causes the upstroke of the action potential 
B)  Occurs during depolarization to threshold 
C)  Occurs after repolarization of the membrane 
D)  Is blocked by tetrodotoxin 
E)  Is blocked by TEA

Question 11

In most cells, Increasing gK would cause

Accepted Answer

A)  Depolarization due to Increased IK 
B)  Depolarization due to Increased EK 
C)  Hyperpolarization due to Increased IK 
D)  Hyperpolarization due to Increased EK 
E)  Hyperpolarization due to decreased Ek

Question 12

A cell has a resting membrane potential of -70 mV and ENa = + 60 mV and EK = - 90 mV. If gNa >0 in this cell,

Accepted Answer

A)  The driving force for Na+ is 60 mV, meaning it will enter the cell 
B)  The driving force for Na+ is 60 m V, m eaning it will exit the cell 
C)  The driving force forNa+ is -10 m V, m eaning it will enter the cell 
D)  The driving force for Na+ is + 10 mV, m eaning it will enter the cell 
E)  The driving force for Na+ is -130 mV, meaning it will enter the cell

Question 13

Repolarization of the nerve during the action potential is caused mainly by

Accepted Answer

A)  Inactivation of the Na channel 
B)  Closing of the K channel 
C)  Opening of the Cl channel 
D)  Activation of the Na channel 
E)  Closing gWHIZ

Question 14

In most cells, Increasing gNa would cause

Accepted Answer

A)  Depolarization due to Increased INa 
B)  Depolarization due to Increased ENa 
C)  Hyperpolarization due to Increased INa 
D)  Hyperpolarization due to Increased ENa 
E)  Hyperpolarization due to decreased ENa

Question 15

In the Hodgkin-Huxley explanation of the action potential, activation gates

Accepted Answer

A)  Are on ly on Na+ channels 
B)  Are only on K+ channels 
C)  Are on both Na+ and K+ channels and have similar kinetics 
D)  Are on both Na+ and K+ channels but Na+ kinetics are slower 
E)  Are on both Na+ and K+ channels but Na+ kinetics are faster

Question 16

At rest, the Na channel

Accepted Answer

A)  Activation gates are closed and inactivation gates are open 
B)  Activation gates are open and inactivation gates are closed 
C)  Both activation and inactivation gates are closed 
D)  Both activation and inactivation gates are open 
E)  None of the above

Question 17

Opening of the Na+ activation gates in motor neurons is caused by

Accepted Answer

A)  Depolarization of the membrane to -50 mV 
B)  Binding of acetylcholine 
C)  Binding of Ca2+ 
D)  Na+ passing through the channel 
E)  Binding of tetrodotoxin

Question 18

The time after an excitation during which the cell can produce another action potential, but it requires a larger than normal stimulus, is called the

Accepted Answer