Question 1

In the sequence of permeability changes for a complete action potential, the first of these events that occurs is the

Accepted Answer

A)  activation of the sodium-potassium "pump." 
B)  inhibition of the sodium-potassium "pump." 
C)  opening of voltage-gated sodium channels. 
D)  closing of voltage-gated potassium channels. 
E)  opening of voltage-gated potassium channels. 
A)  activation of the sodium-potassium "pump." 
B)  inhibition of the sodium-potassium "pump." 
C)  opening of voltage-gated sodium channels. 
D)  closing of voltage-gated potassium channels. 
E)  opening of voltage-gated potassium channels.

Question 2

Ionotropic receptors are found at synapses operated via

Accepted Answer

A)  ligand-gated ion channels. 
B)  metabotropic receptors. 
C)  inhibitory, but not excitatory, synapses. 
D)  excitatory, but not inhibitory, synapses. 
A)  ligand-gated ion channels. 
B)  metabotropic receptors. 
C)  inhibitory, but not excitatory, synapses. 
D)  excitatory, but not inhibitory, synapses.

Question 3

Neural transmission across a mammalian synapse is accomplished by

Accepted Answer

A)  the movement of sodium and potassium ions from the presynaptic neuron into the postsynaptic neuron. 
B)  impulses traveling as electrical currents across the synapse. 
C)  impulses causing the release of a chemical signal and its diffusion across the synapse. 
D)  impulses ricocheting back and forth across the synapse. 
E)  the movement of calcium ions from the presynaptic into the postsynaptic neuron. 
A)  the movement of sodium and potassium ions from the presynaptic neuron into the postsynaptic neuron. 
B)  impulses traveling as electrical currents across the synapse. 
C)  impulses causing the release of a chemical signal and its diffusion across the synapse. 
D)  impulses ricocheting back and forth across the synapse. 
E)  the movement of calcium ions from the presynaptic into the postsynaptic neuron.

Question 4

Most of the neurons in the human brain are

Accepted Answer

A)  sensory neurons. 
B)  motor neurons. 
C)  interneurons. 
D)  nerves. 
A)  sensory neurons. 
B)  motor neurons. 
C)  interneurons. 
D)  nerves.

Question 5

When several inhibitory postsynaptic potentials (IPSPs) arrive at the axon hillock rapidly in sequence from a single dendritic location, hyperpolarizing the postsynaptic cell more and more and thus preventing an action potential, this is an example of

Accepted Answer

A)  temporal summation. 
B)  spatial summation. 
C)  a normal action potential. 
D)  an action potential with an abnormally high peak of depolarization. 
A)  temporal summation. 
B)  spatial summation. 
C)  a normal action potential. 
D)  an action potential with an abnormally high peak of depolarization.

Question 6

Two fundamental concepts about the ion channels of a "resting" neuron are that the channels

Accepted Answer

A)  are always open, but the concentration gradients of ions frequently change. 
B)  are always closed, but ions move closer to the channels during excitation. 
C)  open and close depending on stimuli and are specific as to which ion can traverse them. 
D)  open and close depending on chemical messengers and are nonspecific as to which ion can traverse them. 
E)  open in response to stimuli and then close simultaneously, in unison. 
A)  are always open, but the concentration gradients of ions frequently change. 
B)  are always closed, but ions move closer to the channels during excitation. 
C)  open and close depending on stimuli and are specific as to which ion can traverse them. 
D)  open and close depending on chemical messengers and are nonspecific as to which ion can traverse them. 
E)  open in response to stimuli and then close simultaneously, in unison.

Question 7

What happens when a resting neuron's membrane depolarizes?

Accepted Answer

A)  There is a net diffusion of Na+ out of the cell. 
B)  The equilibrium potential for K+ (EK) becomes more positive. 
C)  The neuron's membrane voltage becomes more positive. 
D)  The cell's inside is more negative than the outside. 
A)  There is a net diffusion of Na+ out of the cell. 
B)  The equilibrium potential for K+ (EK) becomes more positive. 
C)  The neuron's membrane voltage becomes more positive. 
D)  The cell's inside is more negative than the outside.

Question 8

In a simple synapse, neurotransmitter chemicals are received by

Accepted Answer

A)  the postsynaptic dendritic membrane. 
B)  the presynaptic membrane. 
C)  axon hillocks. 
D)  cell bodies. 
A)  the postsynaptic dendritic membrane. 
B)  the presynaptic membrane. 
C)  axon hillocks. 
D)  cell bodies.

Question 9

The activity of acetylcholine in a synapse is terminated by its

Accepted Answer

A)  active transport out of the synaptic cleft. 
B)  diffusion across the presynaptic membrane. 
C)  active transport across the postsynaptic membrane. 
D)  diffusion across the postsynaptic membrane. 
E)  degradation by a hydrolytic enzyme in the synaptic cleft. 
A)  active transport out of the synaptic cleft. 
B)  diffusion across the presynaptic membrane. 
C)  active transport across the postsynaptic membrane. 
D)  diffusion across the postsynaptic membrane. 
E)  degradation by a hydrolytic enzyme in the synaptic cleft.

Question 10

Neurotransmitters affect postsynaptic cells by

Accepted Answer

A)  initiating signal transduction pathways in the cells. 
B)  causing molecular changes in the cells. 
C)  affecting ion-channel proteins. 
D)  altering the permeability of the cells. 
E)  all of the above. 
A)  initiating signal transduction pathways in the cells. 
B)  causing molecular changes in the cells. 
C)  affecting ion-channel proteins. 
D)  altering the permeability of the cells. 
E)  all of the above.

Question 11

Why are action potentials usually conducted in one direction?

Accepted Answer

A)  Ions can flow along the axon in only one direction. 
B)  Voltage-gated Na+ channels are inactivated during the refractory period. 
C)  The axon hillock has a higher membrane potential than the terminals of the axon. 
D)  Voltage-gated channels for both Na+ and K+ open in only one direction. 
A)  Ions can flow along the axon in only one direction. 
B)  Voltage-gated Na+ channels are inactivated during the refractory period. 
C)  The axon hillock has a higher membrane potential than the terminals of the axon. 
D)  Voltage-gated channels for both Na+ and K+ open in only one direction.

Question 12

Tetraethylammonium (TEA) is a potent neurotoxin that results in death from respiratory failure within 10 to 30 minutes. When a neuron is incubated with TEA, researchers observed that action potentials could be generated, but the membrane potential remained positive and never returned to the resting membrane potential. What channels could be opened that would counter the effects of TEA and allow the neuron to return to resting membrane potential?

Accepted Answer

A)  chloride channels 
B)  calcium channels 
C)  sodium channels 
D)  There are no channels that can oppose the effects of TEA. 
A)  chloride channels 
B)  calcium channels 
C)  sodium channels 
D)  There are no channels that can oppose the effects of TEA.

Question 13

Action potentials move along axons

Accepted Answer

A)  more slowly in axons of large diameter as compared to those of small diameter. 
B)  by the direct action of acetylcholine on the axonal membrane. 
C)  by activating the sodium-potassium "pump" at each point along the axonal membrane. 
D)  more rapidly in myelinated than in nonmyelinated axons. 
E)  by reversing the concentration gradients for sodium and potassium ions. 
A)  more slowly in axons of large diameter as compared to those of small diameter. 
B)  by the direct action of acetylcholine on the axonal membrane. 
C)  by activating the sodium-potassium "pump" at each point along the axonal membrane. 
D)  more rapidly in myelinated than in nonmyelinated axons. 
E)  by reversing the concentration gradients for sodium and potassium ions.

Question 14

The membrane potential that exactly offsets an ion's concentration gradient is called the

Accepted Answer

A)  graded potential. 
B)  threshold potential. 
C)  equilibrium potential. 
D)  action potential. 
E)  inhibitory postsynaptic potential. 
A)  graded potential. 
B)  threshold potential. 
C)  equilibrium potential. 
D)  action potential. 
E)  inhibitory postsynaptic potential.

Question 15

Please use the following information to answer the question(s) below.
Curare is a potent neurotoxin extracted from the Strychnos toxifera plant in Central and South America. Indigenous peoples of South America apply curare to arrows, which they used to hunt and kill animals. Curare acts at synapses between motor neurons and skeletal muscle cells. When a motor neuron synapses with a skeletal muscle cell, the skeletal muscle cell may be stimulated or inhibited just like postsynaptic neurons are. Curare acts by binding temporarily to acetylcholine receptors on the postsynaptic cell and prevents acetylcholine from binding.
-What effect does curare likely have on the postsynaptic cell?

Accepted Answer

A)  prevents voltage-gated sodium channels from opening 
B)  hyperpolarizes the postsynaptic cell 
C)  stimulates muscle contraction 
D)  depolarizes the presynaptic cell 
A)  prevents voltage-gated sodium channels from opening 
B)  hyperpolarizes the postsynaptic cell 
C)  stimulates muscle contraction 
D)  depolarizes the presynaptic cell

Question 16

Opening all of the sodium channels, with all other ion channels closed - which is an admittedly artificial setting - on an otherwise typical neuron should move its membrane potential to

Accepted Answer

A)  -90 mV. 
B)  -70 mV. 
C)  0 mV. 
D)  +30 mV. 
E)  +62 mV. 
A)  -90 mV. 
B)  -70 mV. 
C)  0 mV. 
D)  +30 mV. 
E)  +62 mV.

Question 17

The fastest possible conduction velocity of action potentials is observed in

Accepted Answer

A)  thin, nonmyelinated neurons. 
B)  thin, myelinated neurons. 
C)  thick, nonmyelinated neurons. 
D)  thick, myelinated neurons. 
A)  thin, nonmyelinated neurons. 
B)  thin, myelinated neurons. 
C)  thick, nonmyelinated neurons. 
D)  thick, myelinated neurons.

Question 18

Tetraethylammonium (TEA) is a potent neurotoxin that results in death from respiratory failure within 10 to 30 minutes. When a neuron is incubated with TEA, researchers observed that action potentials could be generated, but the membrane potential remained positive and never returned to the resting membrane potential. What channel is TEA likely acting on?

Accepted Answer

A)  voltage-gated sodium channels 
B)  voltage-gated potassium channels 
C)  sodium potassium pumps 
D)  chloride channels 
A)  voltage-gated sodium channels 
B)  voltage-gated potassium channels 
C)  sodium potassium pumps 
D)  chloride channels

Question 19

In Figure 37.1, at what point in the graph are sodium channels closed (or closing) and potassium channels opened?

Accepted Answer

A)  A. 
B)  B. 
C)  C. 
D)  D. 
E)  E. 
A)  A. 
B)  B. 
C)  C. 
D)  D. 
E)  E.

Question 20

Figure 37.1
-In Figure 37.1, the membrane potential is closest to the equilibrium potential for potassium at label

Accepted Answer

A)  A. 
B)  B. 
C)  C. 
D)  D. 
E)  E. 
A)  A. 
B)  B. 
C)  C. 
D)  D. 
E)  E.

Exam 37: Neurons, Synapses, and Signaling

In the sequence of permeability changes for a complete action potential, the first of these events that occurs is the

Ionotropic receptors are found at synapses operated via

Neural transmission across a mammalian synapse is accomplished by

Most of the neurons in the human brain are

When several inhibitory postsynaptic potentials (IPSPs) arrive at the axon hillock rapidly in sequence from a single dendritic location, hyperpolarizing the postsynaptic cell more and more and thus preventing an action potential, this is an example of

Two fundamental concepts about the ion channels of a "resting" neuron are that the channels

What happens when a resting neuron's membrane depolarizes?

In a simple synapse, neurotransmitter chemicals are received by

The activity of acetylcholine in a synapse is terminated by its

Neurotransmitters affect postsynaptic cells by

Why are action potentials usually conducted in one direction?

Action potentials move along axons

The membrane potential that exactly offsets an ion's concentration gradient is called the

Opening all of the sodium channels, with all other ion channels closed - which is an admittedly artificial setting - on an otherwise typical neuron should move its membrane potential to

The fastest possible conduction velocity of action potentials is observed in

In Figure 37.1, at what point in the graph are sodium channels closed (or closing) and potassium channels opened?

Figure 37.1 -In Figure 37.1, the membrane potential is closest to the equilibrium potential for potassium at label

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