Deck 18: The Action Potential

Question 1

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

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

Answer 1

A

Question 2

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

A) Depolarization of the membrane to -50 mV
B) Binding of acetylcholine
C) Binding of Ca₂+
D) Na+ passing through the channel
E) Bin din g o f te tro do tox in

Answer 2

A

Question 3

The "overshoot" of the action potential means

A) The m embrane potential mom entarily becomes m ore negative than EK
B) The m embrane potential mom entarily becomes more positive than ENa
C) Em momentarily becomes positive
D) Em becomes m ore positive than ECl
E) Fo r a brie f m om ent E m is not described by the chord conductance equation

Answer 3

C

Question 4

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

A) The driving force for Na+ is 60 mV , m ea nin g it w ill en ter the ce ll
B) The driving force for Na+ is 6 0 m V, m ea nin g it w ill ex it the ce ll
C) The driving force for Na+ is -1 0 m V, m ea nin g it w ill en ter the ce ll
D) The driving force for Na+ is + 10 m V, m ea nin g it w ill en ter the ce ll
E) The driving force for Na+ is -13 0 m V, m ean ing it w ill ente r the cell

Question 5

In most cells, Increasing gK would cause

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 6

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

A) Repolarization
B) K+ current
C) T ime
D) Depolarization
E) Bo th repolarization and time

Question 7

Opening of the inactivation gate of the Na channel

A) Causes the upstroke of the action potential
B) O cc ur s d ur ing de po lar izat ion to th re sh old
C) Occurs after repolarization of the membrane
D) Is b loc ke d b y tetr od oto xin
E) Is blocked by TEA

Question 8

The E m for a cell is -70 mV and ECl is -80 mV. Increasing gCl should Increase

A) The driving force for Cl-
B) Outward flux of Cl- and an inward current to d ep ola rize the ce ll
C) Inward flux of Cl- and an o utw ard cur ren t tha t hyp erp olar izes the cell
D) Inward flux of Cl- an d a n in wa rd cu rre nt to de po lar ize th e c ell
E) Outward flux of Cl- an d a n o utw ar d c ur re nt to hyp er po lar ize th e c ell

Question 9

At rest, the Na channel

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 10

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

A) Are on ly on Na+ ch an ne ls
B) Are only on K+ ch an ne ls
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 11

De pola rization re fers to

A) Mak ing the me m brane poten tial m ore negative
B) R ota tion of t he ce ll co un ter clo ck wis e a bo ut th e its ax is
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 12

"Late ncy" re fers to the

A) Delay between Increase in gNa and gK du rin g th e a ctio n p ote ntia l
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 13

The first step in the nerve action potential from rest is

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 mem brane

Question 14

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

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

Question 15

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

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

Question 16

In most cells, Increasing gNa would cause

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 17

Suppose that af ter an action pote ntial we clam p the m em bran e po tential at - 50 mV a nd do n't le t it co m ple tely repo larize. W e fin d th at w e c an no t elic it an ac tion po ten tial. This is called a depolarization bloc k. W hat c aus es it?

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 18

The time after an ex cita tion du rin g w hic h th e c ell c an no t pr od uc e a no the r ac tion po ten tial is called the

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