HCS 215 Chapter 7 Test Bank Questions With Complete
Solutions
50) The all-or-none principle, associated with the action
potential, states that
A) the positive feedback loop for the sodium channel is
terminated by the inactivation gate.
B) there is a positive feedback loop for sodium channels that
results in a rapid membrane depolarization.
C) all of the action potentials will be generated from the axon
hillock.
D) once membrane potential reaches threshold, an action
potential will be generated and that action potential will always
be the same magnitude.
E) following an action potential, the membrane will be
repolarized by the opening of a potassium channel. Correct
Answers D
51) Toward the end of the relative refractory period, the
continued decrease in stimulus intensity required to initiate an
action potential is caused by
A) decreased sodium permeability.
B) increased potassium permeability.
C) closure of the sodium activation gate.
D) decreased potassium permeability.
E) the number of sodium channels whose inactivation gate has
not opened. Correct Answers D
52) Which statement below best describes why action potentials
travel in only one direction?
A) The all-or-none principle explains this.
,B) They have a refractory period.
C) The diameter of the axon explains this.
D) Only sodium- and potassium-gated channels are found on the
axon.
E) They have myelinated axons. Correct Answers B
53) How can action potentials relay information about the
intensity of a stimulus, such as distinguishing between a loud
and soft sound?
A) due to the frequency of action potentials
B) due to the magnitude of action potentials
C) due to summation of several action potentials
D) due to electrotonic conduction
E) due to the decremental properties of graded potentials
Correct Answers A
54) What limits the maximum number of action potentials on an
axon?
A) the concentration of sodium within the cytoplasm of the cell
B) the absolute refractory period
C) the relative refractory period
D) whether the axon is myelinated or not
E) the diameter of the axon Correct Answers B
55) For an unmyelinated axon, conduction velocity is primarily
determined by the
A) type of potassium channel activated.
B) type of sodium channel activated.
C) diameter of the axon.
D) permeability of the axonal membrane.
, E) number of ion channels present on the membrane. Correct
Answers C
56) As an action potential is propagated away from the axon
hillock, why does propagation continue in one direction?
A) The region just behind the action potential is in the absolute
refractory period.
B) The region just in front of the action potential is in the
absolute refractory period.
C) The region just behind the action potential is in the relative
refractory period.
D) The region just in front of the action potential is in the
relative refractory period.
E) They will travel the path of least resistance. Correct Answers
A
57) ________ is the mechanism by which action potentials are
propagated in unmyelinated axons.
A) The all-or-none principle
B) The regenerative mechanism
C) After-hyperpolarization
D) Temporal summation
E) Electrotonic conduction Correct Answers E
58) In myelinated nerve fibers, where do action potentials
occur?
A) cell body
B) nodes of Ranvier
C) Schwann cell
D) underlying myelin sheath
E) oligodendrocyte Correct Answers B
Solutions
50) The all-or-none principle, associated with the action
potential, states that
A) the positive feedback loop for the sodium channel is
terminated by the inactivation gate.
B) there is a positive feedback loop for sodium channels that
results in a rapid membrane depolarization.
C) all of the action potentials will be generated from the axon
hillock.
D) once membrane potential reaches threshold, an action
potential will be generated and that action potential will always
be the same magnitude.
E) following an action potential, the membrane will be
repolarized by the opening of a potassium channel. Correct
Answers D
51) Toward the end of the relative refractory period, the
continued decrease in stimulus intensity required to initiate an
action potential is caused by
A) decreased sodium permeability.
B) increased potassium permeability.
C) closure of the sodium activation gate.
D) decreased potassium permeability.
E) the number of sodium channels whose inactivation gate has
not opened. Correct Answers D
52) Which statement below best describes why action potentials
travel in only one direction?
A) The all-or-none principle explains this.
,B) They have a refractory period.
C) The diameter of the axon explains this.
D) Only sodium- and potassium-gated channels are found on the
axon.
E) They have myelinated axons. Correct Answers B
53) How can action potentials relay information about the
intensity of a stimulus, such as distinguishing between a loud
and soft sound?
A) due to the frequency of action potentials
B) due to the magnitude of action potentials
C) due to summation of several action potentials
D) due to electrotonic conduction
E) due to the decremental properties of graded potentials
Correct Answers A
54) What limits the maximum number of action potentials on an
axon?
A) the concentration of sodium within the cytoplasm of the cell
B) the absolute refractory period
C) the relative refractory period
D) whether the axon is myelinated or not
E) the diameter of the axon Correct Answers B
55) For an unmyelinated axon, conduction velocity is primarily
determined by the
A) type of potassium channel activated.
B) type of sodium channel activated.
C) diameter of the axon.
D) permeability of the axonal membrane.
, E) number of ion channels present on the membrane. Correct
Answers C
56) As an action potential is propagated away from the axon
hillock, why does propagation continue in one direction?
A) The region just behind the action potential is in the absolute
refractory period.
B) The region just in front of the action potential is in the
absolute refractory period.
C) The region just behind the action potential is in the relative
refractory period.
D) The region just in front of the action potential is in the
relative refractory period.
E) They will travel the path of least resistance. Correct Answers
A
57) ________ is the mechanism by which action potentials are
propagated in unmyelinated axons.
A) The all-or-none principle
B) The regenerative mechanism
C) After-hyperpolarization
D) Temporal summation
E) Electrotonic conduction Correct Answers E
58) In myelinated nerve fibers, where do action potentials
occur?
A) cell body
B) nodes of Ranvier
C) Schwann cell
D) underlying myelin sheath
E) oligodendrocyte Correct Answers B
