BMSC 207 FINAL REVIEW QUESTIONS & ANSWERS
What neuron is NOT a apart of the efferent pathway? - Answers -Sensory
The sympathetic and parasympathetic nervous system are divisions of what system? -
Answers -The autonomic nervous system
Which glial cells from myelin in the central nervous system? - Answers -
Oligodendrocytes
What is a difference between the synaptic cleft and the synapse? - Answers -The
synaptic cleft is the space between a presynaptic axon terminal and the postsynaptic
dendrite, and a synapse includes all three of these structures.
The neurons of the central nervous system are also known as - Answers -interneurons
Where in the neuron is an action potential initially generated? - Answers -Axon Hillock
The depolarization phase of an action potential results from the opening of which
channels? - Answers -voltage gated Na+ channels
The repolarization phase of an action potential results from? - Answers -The opening of
voltage gated K+ channels
Hyperpolarization results from? - Answers -slow closing of voltage-gated K+ channels
What is the magnitude (amplitude) of an action potential? - Answers -100mV
How is an action potential propagated along an axon? - Answers -An influx of sodium
ions from the current action potential depolarizes the adjacent area.
Why does the action potential only move away from the cell body? - Answers -The
areas that have had the action potential are refractory to a new action potential.
The velocity of the action potential is fastest in which of the following axons? - Answers
-a small myelinated axon
What opens first in response to a threshold stimulus? - Answers -Voltage-gated Na+
channels
What characterizes depolarization, the first phase of the action potential? - Answers -
The membrane potential changes from a negative value to a positive value.
Submit
,What characterizes repolarization, the second phase of the action potential? - Answers
-Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its
negative resting value of -70 mV.
What event triggers the generation of an action potential? - Answers -The membrane
potential must depolarize from the resting voltage of -70 mV to a threshold value of -55
mV.
What is the first change to occur in response to a threshold stimulus? - Answers -
Voltage-gated Na+ channels change shape, and their activation gates open.
What type of conduction takes place in unmyelinated axons? - Answers -Continuous
conduction
An action potential is self-regenerating because __________. - Answers -depolarizing
currents established by the influx of Na+ flow down the axon and trigger an action
potential at the next segment
Why does regeneration of the action potential occur in one direction, rather than in two
directions? - Answers -The inactivation gates of voltage-gated Na+ channels close in
the node, or segment, that has just fired an action potential.
What is the function of the myelin sheath? - Answers -The myelin sheath increases the
speed of action potential conduction from the initial segment to the axon terminals.
What changes occur to voltage-gated Na+ and K+ channels at the peak of
depolarization? - Answers -Inactivation gates of voltage-gated Na+ channels close,
while activation gates of voltage-gated K+ channels open.
In which type of axon will velocity of action potential conduction be the fastest? -
Answers -Myelinated axons with the largest diameter
During an action potential, the rapid decrease in sodium ion permeability and the
simultaneous and rapid increase in potassium ion permeability is responsible for
__________. - Answers -the repolarization phase
During an action potential, when does sodium ion permeability begin to significantly
decline? - Answers -at the peak of depolarization
Which membrane potential opens a sufficient number of the voltage-gated Na+
channels to cause a significant change in the membrane potential (making it much less
negative) - Answers --60mV
A stronger stimulus to a neuron results in __________. - Answers -stronger graded
potentials
, Whether a neuron fires an action potential depends on __________. - Answers -a
graded potential above threshold voltage reaching the trigger zone
Which of the following would have the fastest action potentials? - Answers -A
myelinated axon with a large diameter
What would happen to the membrane potential if a resting cell suddenly became more
permeable to Ca++? - Answers -It would depolarize.
During an action potential, activation of voltage-gated sodium and potassium channels
occurs at different rates. What is the effect of this difference on ion flow across an axon
membrane? - Answers -Initially, Na+ flows into the cell and then K+ flows out of the
cell.
What would the sudden increase in axonal permeability to sodium cause? - Answers -
The rising phase of an action potential
Why is an action potential conducted in only one direction, from an axon hillock to an
axon terminal? - Answers -The membrane channels are refractory and cannot open.
Which two properties determine how fast neurons conduct action potentials? - Answers
-Axon diameter and the leak resistance of the membrane
What triggers exocytosis of synaptic vesicle contents from an axon terminal? - Answers
-The opening of voltage-gated Ca2+ channels
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which
neurotransmitter? - Answers -acetylcholine (ACh)
When an action potential arrives at the axon terminal of a motor neuron, which ion
channels open? - Answers -voltage-gated calcium channels
What means of membrane transport is used to release the neurotransmitter into the
synaptic cleft? - Answers -exocytosis
The binding of the neurotransmitter to receptors on the motor end plate causes which of
the following to occur? - Answers -Binding of the neurotransmitter causes chemically
gated sodium channels to open in the motor end plate (junctional folds of the
sarcolemma) and sodium enters the cell.
How is acetylcholine (ACh) removed from the synaptic cleft? - Answers -simple
diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)
The action potential on the muscle cell leads to contraction due to the release of
calcium ions. Where are calcium ions stored in the muscle cell? - Answers -terminal
cisterns (cisternae) of the sarcoplasmic reticulum
What neuron is NOT a apart of the efferent pathway? - Answers -Sensory
The sympathetic and parasympathetic nervous system are divisions of what system? -
Answers -The autonomic nervous system
Which glial cells from myelin in the central nervous system? - Answers -
Oligodendrocytes
What is a difference between the synaptic cleft and the synapse? - Answers -The
synaptic cleft is the space between a presynaptic axon terminal and the postsynaptic
dendrite, and a synapse includes all three of these structures.
The neurons of the central nervous system are also known as - Answers -interneurons
Where in the neuron is an action potential initially generated? - Answers -Axon Hillock
The depolarization phase of an action potential results from the opening of which
channels? - Answers -voltage gated Na+ channels
The repolarization phase of an action potential results from? - Answers -The opening of
voltage gated K+ channels
Hyperpolarization results from? - Answers -slow closing of voltage-gated K+ channels
What is the magnitude (amplitude) of an action potential? - Answers -100mV
How is an action potential propagated along an axon? - Answers -An influx of sodium
ions from the current action potential depolarizes the adjacent area.
Why does the action potential only move away from the cell body? - Answers -The
areas that have had the action potential are refractory to a new action potential.
The velocity of the action potential is fastest in which of the following axons? - Answers
-a small myelinated axon
What opens first in response to a threshold stimulus? - Answers -Voltage-gated Na+
channels
What characterizes depolarization, the first phase of the action potential? - Answers -
The membrane potential changes from a negative value to a positive value.
Submit
,What characterizes repolarization, the second phase of the action potential? - Answers
-Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its
negative resting value of -70 mV.
What event triggers the generation of an action potential? - Answers -The membrane
potential must depolarize from the resting voltage of -70 mV to a threshold value of -55
mV.
What is the first change to occur in response to a threshold stimulus? - Answers -
Voltage-gated Na+ channels change shape, and their activation gates open.
What type of conduction takes place in unmyelinated axons? - Answers -Continuous
conduction
An action potential is self-regenerating because __________. - Answers -depolarizing
currents established by the influx of Na+ flow down the axon and trigger an action
potential at the next segment
Why does regeneration of the action potential occur in one direction, rather than in two
directions? - Answers -The inactivation gates of voltage-gated Na+ channels close in
the node, or segment, that has just fired an action potential.
What is the function of the myelin sheath? - Answers -The myelin sheath increases the
speed of action potential conduction from the initial segment to the axon terminals.
What changes occur to voltage-gated Na+ and K+ channels at the peak of
depolarization? - Answers -Inactivation gates of voltage-gated Na+ channels close,
while activation gates of voltage-gated K+ channels open.
In which type of axon will velocity of action potential conduction be the fastest? -
Answers -Myelinated axons with the largest diameter
During an action potential, the rapid decrease in sodium ion permeability and the
simultaneous and rapid increase in potassium ion permeability is responsible for
__________. - Answers -the repolarization phase
During an action potential, when does sodium ion permeability begin to significantly
decline? - Answers -at the peak of depolarization
Which membrane potential opens a sufficient number of the voltage-gated Na+
channels to cause a significant change in the membrane potential (making it much less
negative) - Answers --60mV
A stronger stimulus to a neuron results in __________. - Answers -stronger graded
potentials
, Whether a neuron fires an action potential depends on __________. - Answers -a
graded potential above threshold voltage reaching the trigger zone
Which of the following would have the fastest action potentials? - Answers -A
myelinated axon with a large diameter
What would happen to the membrane potential if a resting cell suddenly became more
permeable to Ca++? - Answers -It would depolarize.
During an action potential, activation of voltage-gated sodium and potassium channels
occurs at different rates. What is the effect of this difference on ion flow across an axon
membrane? - Answers -Initially, Na+ flows into the cell and then K+ flows out of the
cell.
What would the sudden increase in axonal permeability to sodium cause? - Answers -
The rising phase of an action potential
Why is an action potential conducted in only one direction, from an axon hillock to an
axon terminal? - Answers -The membrane channels are refractory and cannot open.
Which two properties determine how fast neurons conduct action potentials? - Answers
-Axon diameter and the leak resistance of the membrane
What triggers exocytosis of synaptic vesicle contents from an axon terminal? - Answers
-The opening of voltage-gated Ca2+ channels
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which
neurotransmitter? - Answers -acetylcholine (ACh)
When an action potential arrives at the axon terminal of a motor neuron, which ion
channels open? - Answers -voltage-gated calcium channels
What means of membrane transport is used to release the neurotransmitter into the
synaptic cleft? - Answers -exocytosis
The binding of the neurotransmitter to receptors on the motor end plate causes which of
the following to occur? - Answers -Binding of the neurotransmitter causes chemically
gated sodium channels to open in the motor end plate (junctional folds of the
sarcolemma) and sodium enters the cell.
How is acetylcholine (ACh) removed from the synaptic cleft? - Answers -simple
diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)
The action potential on the muscle cell leads to contraction due to the release of
calcium ions. Where are calcium ions stored in the muscle cell? - Answers -terminal
cisterns (cisternae) of the sarcoplasmic reticulum
