Deck 37: Neurons,synapses,and Signaling

Question 1

The cell body of a neuron contains

A)the nucleus and most organelles.
B)dendrites.
C)the axon.
D)synaptic vesicles about to be released at the synapse.

Answer 1

A

Question 2

The operation of the sodium-potassium "pump" moves sodium ions ________ the cell and potassium ions ________ the cell.

A)into;out of
B)out of;into
C)into;into
D)out of;out of

Answer 2

B

Question 3

Somatic motor neurons are used to transmit motor signals to muscles.For example,a somatic motor neuron carries a signal from your spinal cord to your biceps brachii so that you can flex your arm at the elbow.In this example,what is the correct sequence of neuronal structures that this signal would travel through in the motor neuron?

A)dendrites,cell body,axon,axon hillock,synaptic terminals,biceps brachii
B)dendrites,cell body,axon hillock,axon,synaptic terminals,biceps brachii
C)axon,cell body,synaptic terminals,dendrites,axon hillock,biceps brachii
D)synaptic terminals,dendrites,cell body,axon,axon hillock,biceps brachii

Answer 3

B

Question 4

Self-propagation and refractory periods are typical of

A)action potentials.
B)graded hyperpolarizations.
C)excitatory postsynaptic potentials.
D)inhibitory postsynaptic potentials.
E)resting potentials.

Question 5

A simple nervous system

A)must include chemical senses and vision.
B)includes sensory information but no effectors.
C)has information flow in only one direction: toward an integrating center.
D)has information flow in only one direction: away from an integrating center.
E)includes sensory information,an integrating center,and effectors.

Question 6

In a simple synapse,neurotransmitter chemicals are released by

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

Question 7

A synapse is

A)a single long extension off the cell body of a neuron.
B)the point of connection between two communicating neurons.
C)one of many extensions off a cell body that receives signals from other neurons.
D)the location where action potentials are generated.

Question 8

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

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 9

A graded hyperpolarization of a membrane can be induced by

A)increasing its membrane's permeability to Na⁺.
B)decreasing its membrane's permeability to H⁺.
C)decreasing its membrane's permeability to Cl^-.
D)increasing its membrane's permeability to Ca²⁺.
E)increasing its membrane's permeability to K⁺.

Question 10

Suppose you are a researcher examining the impacts of ion channels on resting membrane potential in typical neurons.By using a drug,you artificially open all sodium channels and keep all other ion channels closed.What value of the resting membrane potential should you observe?

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

Question 11

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

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

Question 12

The selectivity of a particular ion channel refers to its

A)permitting passage by positive but not negative ions.
B)permitting passage by negative but not positive ions.
C)ability to change its size depending on the ion needing transport.
D)binding with only one type of neurotransmitter.
E)permitting passage only to a specific ion.

Question 13

A drug that specifically inhibits voltage-gated sodium channels in axons would be expected to

A)prevent the hyperpolarization phase of the action potential.
B)prevent the depolarization phase of the action potential.
C)prevent graded potentials.
D)increase the release of neurotransmitter molecules.
E)have most of its effects on the dendritic region of a neuron.

Question 14

Most of the neurons in the human brain are

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

Question 15

Action potentials move along axons

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 16

A cation that is more abundant as a solute in the cytosol of a neuron than it is in the interstitial fluid outside the neuron is

A)HCO₃^-.
B)Cl^-.
C)Ca²⁺.
D)Na⁺.
E)K⁺.

Question 17

The "threshold" potential of a membrane is the

A)maximum depolarization needed to operate sodium-potassium pumps.
B)lowest frequency of action potentials a neuron can produce.
C)minimum hyperpolarization needed to prevent the occurrence of action potentials.
D)minimum depolarization needed to operate the voltage-gated sodium and potassium channels.
E)peak amount of depolarization seen in an action potential.

Question 18

Although the membrane of a "resting" neuron is highly permeable to potassium ions,its membrane potential does not exactly match the equilibrium potential for potassium because the neuronal membrane is also

A)fully permeable to sodium ions.
B)slightly permeable to sodium ions.
C)fully permeable to calcium ions.
D)impermeable to sodium ions.
E)highly permeable to chloride ions.

Question 19

For a neuron with an initial membrane potential at -70 mV,an increase in the movement of potassium ions out of that neuro's cytoplasm would result in the

A)depolarization of the neuron.
B)hyperpolarization of the neuron.
C)replacement of potassium ions with sodium ions.
D)replacement of potassium ions with calcium ions.
E)neuron switching on its sodium-potassium pump to restore the initial conditions.

Question 20

ATP hydrolysis,and the binding of a phosphate to the pump,directly powers the movement of

A)K⁺ out of cells.
B)Na⁺ out of cells.
C)Na⁺into cells.
D)Ca²⁺ into cells.
E)Cl^- into cells.

Question 21

When a membrane is in its refractory period,

A)it is not possible to generate a second action potential.
B)it is at the equilibrium potential.
C)it is above threshold.
D)all of its voltage-gated potassium channels are open.

Question 22

The observation that the acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium channel and opens it is an example of a

A)voltage-gated sodium channel.
B)voltage-gated potassium channel.
C)ligand-gated sodium channel.
D)second-messenger-gated sodium channel.
E)chemical that inhibits action potentials.

Question 23

Neurotransmitters that hyperpolarize neuron membranes are categorized as

A)excitatory.
B)inhibitory.
C)neutral.

Question 24

The following steps refer to various stages in transmission at a chemical synapse.
1)Neurotransmitters bind with receptors associated with the postsynaptic membrane.
2)Calcium ions rush into the neuron's cytoplasm.
3)An action potential depolarizes the membrane of the axon terminal.
4)The ligand-gated ion channels open.
5)The synaptic vesicles release neurotransmitters into the synaptic cleft.
Which sequence of events is correct?

A)1 → 2 → 3 → 4 → 5
B)2 → 3 → 5 → 4 → 1
C)3 → 2 → 5 → 1 → 4
D)4 → 3 → 1 → 2 → 5
E)5 → 1 → 2 → 4 → 3

Question 25

After the depolarization phase of an action potential,the resting potential is restored by

A)the opening of voltage-gated sodium channels.
B)the opening of voltage-gated potassium channels and the closing of sodium channels.
C)a decrease in the membrane's permeability to potassium and chloride ions.
D)a brief inhibition of the sodium-potassium pump.
E)the opening of more voltage-gated sodium channels.

Question 26

The fastest possible conduction velocity of action potentials is observed in

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

Question 27

An action potential can start in the middle of an axon and proceed to both opposite directions when

A)the neuron is an inhibitory neuron and operating normally.
B)only the middle section of the axon has been artificially stimulated by an electrode.
C)the dendritic region fires an action potential.
D)it is in its typical refractory state.
E)its membrane potential is above the threshold.

Question 28

Ionotropic receptors are found at synapses operated via

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

Question 29

Action potentials are normally carried in only one direction: from the axon hillock toward the axon terminals.If you experimentally depolarize the middle of the axon to threshold,then

A)no action potential will be initiated.
B)an action potential will be initiated and proceed only in the normal direction toward the axon terminal.
C)an action potential will be initiated and proceed only back toward the axon hillock.
D)two action potentials will be initiated,one going toward the axon terminal and one going back toward the hillock.
E)an action potential will be initiated,but it will die out before it reaches the axon terminal.

Question 30

Neural transmission across a mammalian synapse is accomplished by

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 31

The activity of acetylcholine in a synapse is terminated by its

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 32

The "undershoot" phase of after-hyperpolarization is due to

A)slow opening of voltage-gated sodium channels.
B)sustained opening of voltage-gated potassium channels.
C)rapid opening of voltage-gated calcium channels.
D)slow restorative actions of the sodium-potassium ATPase.
E)ions that move away from their open ion channels.

Question 33

If a membrane is made more permeable to ________,then an inhibitory postsynaptic potential (IPSP)will occur.

A)potassium ions
B)sodium ions
C)calcium ions

Question 34

Which of the following principles characterize gated ion channels in the neuronal membrane? Select all that apply.
I)Channels are always open.
II)Channels are always closed.
III)Channels open and close depending on stimuli.
IV)Channels are specific to which ions can traverse them.
V)Channels are nonspecific to which ions can traverse them.

A)I and V only
B)II and IV only
C)III and IV only
D)II and V only
E)III and V only

Question 35

The nervous system can alter the activities of skeletal muscle fibers because

A)it is electrically coupled by gap junctions to the muscles.
B)its signals bind to receptor proteins on the muscles.
C)its signals reach the muscles via the blood.
D)its light pulses activate contraction in the muscles.
E)it is connected to the internal neural network of the muscles.

Question 36

The surface on a neuron that discharges the contents of synaptic vesicles is the

A)dendrite.
B)axon hillock.
C)node of Ranvier.
D)postsynaptic membrane.
E)presynaptic membrane.

Question 37

Saltatory conduction is a term applied to

A)conduction of impulses across electrical synapses.
B)an action potential that skips the axon hillock when it moves from the dendritic region to the axon terminal.
C)the rapid movement of an action potential reverberating back and forth along a neuron.
D)jumping from one neuron to an adjacent neuron.
E)jumping from one node of Ranvier to the next in a myelinated neuron.

Question 38

In a simple synapse,neurotransmitter chemicals are received by

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

Question 39

Researchers created a genetic strain of mice that were lacking both genes for MyRF,a transcription factor that is required for oligodendrocytes to function normally.What is the most likely effect that this would have on the mice?

A)loss of salutatory conduction
B)thicker myelin sheaths
C)impaired ability for potassium ions to cross neuronal membranes
D)growth of dendrites

Question 40

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

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 41

GABA is

A)a chemical that affects neuronal function but is not stored in presynaptic vesicles.
B)an amino acid that operates at inhibitory synapses in the brain.
C)a neuropeptide that might function as a natural analgesic.
D)the major inhibitory neurotransmitter of the human brain.

Question 42

Neurotransmitters affect postsynaptic cells by (select all that apply)
I)initiating signal transduction pathways in the cells.
II)causing molecular changes in the cells.
III)affecting ion-channel proteins.
IV)altering the permeability of the cells.

A)II only
B)I and III only
C)II,III,and IV only
D)I,II,and III only
E)I,II,III,and IV

Question 43

The autonomic nervous system innervates cardiac muscle,smooth muscles,and glands and is analogous to the part of the nervous system that innervates skeletal muscle.What type of neuron would innervate structures via the autonomic nervous system?

A)sensory neuron
B)motor neuron
C)interneuron

Question 44

________ occurs 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.

A)Temporal summation
B)Spatial summation
C)A normal action potential

Question 45

An endorphin is

A)a chemical that affects neuronal function but is not stored in presynaptic vesicles.
B)an amino acid that operates at inhibitory synapses in the brain.
C)a neuropeptide that might function as a natural analgesic.
D)the major inhibitory neurotransmitter of the human brain.

Question 46

Most of the synapses in vertebrates conduct information in only one direction

A)as a result of the nodes of Ranvier.
B)as a result of voltage-gated sodium channels found only in the vertebrate system.
C)because vertebrate nerve cells have dendrites.
D)because only the postsynaptic cells can bind and respond to neurotransmitters.
E)because the sodium-potassium pump moves ions in one direction.

Question 47

Alexander disease is a type of leukodystrophy in which myelin sheaths surrounding axons in the brain are destroyed.What type of cell is affected,and what is the outcome in Alexander disease?

A)Schwann cells are affected,and action potential propagation is slowed.
B)Oligodendrocytes are affected,and action potential propagation is slowed.
C)Schwann cells are affected,and action potential propagation is sped up.
D)Oligodendrocytes are affected,and action potential propagation is sped up.

Question 48

Functionally,which cellular location is the neuron's "decision-making site" as to whether or not an action potential will be initiated?

A)axonal membrane
B)axon hillock
C)dendritic membrane

Question 49

Receptors for neurotransmitters are of primary functional importance in assuring one-way synaptic transmission because they are mostly found on the

A)axonal membrane.
B)axon hillock.
C)postsynaptic dendritic membrane.
D)presynaptic membrane.

Question 50

Assume that excessive consumption of ethanol increases the influx of negative chloride ions into "commonsense" neurons whose action potentials are needed for you to act appropriately and not harm yourself or others.Thus,any resulting poor decisions associated with ethanol ingestion are likely due to

A)increased membrane depolarization of "commonsense" neurons.
B)increased membrane hyperpolarization of "commonsense" neurons.
C)more action potentials in your "commonsense" neurons.
D)more EPSPs in your "commonsense" neurons.
E)fewer IPSPs in your "commonsense" neurons.

Question 51

Neurons can be classified according to structure as well as function.If a neuron has a single projection from the cell body,it is a unipolar neuron.If it has two projections,it is a bipolar neuron.Finally,if it has more than two projections,it is a multipolar neuron.What structural type of neuron is a motor neuron?

A)unipolar neuron
B)bipolar neuron
C)multipolar neuron

Question 52

Motor neurons alter skeletal muscle activities by releasing neurotransmitters because

A)they are electrically coupled by gap junctions to the muscles.
B)their signals bind to receptor proteins on the muscles.
C)their signals reach the muscles via the blood.
D)their light pulses activate contraction in the muscles.
E)they are connected to the internal neural network of the muscles.

Question 53

Neurons can be classified according to structure as well as function.If a neuron has a single projection from the cell body,it is a unipolar neuron.If it has two projections,it is a bipolar neuron.Finally,if it has more than two projections,it is a multipolar neuron.What structural type of neuron is an interneuron?

A)unipolar neuron
B)bipolar neuron
C)multipolar neuron

Question 54

Figure 37.2
Figure 37.2 shows many channels in a neuron membrane.The channel third from the left is a voltage-gated sodium channel.What would happen if this channel became blocked and thus unable to function?

A)The cell's membrane potential would not change.
B)The cell would hyperpolarize.
C)The cell would depolarize.

Question 55

________ occurs when several excitatory postsynaptic potentials (EPSPs)arrive at the axon hillock from different dendritic locations and then depolarize the postsynaptic cell to threshold for an action potential

A)Temporal summation
B)Spatial summation
C)A normal action potential

Question 56

What will happen if a neuron membrane suddenly becomes permeable to chloride ions?

A)Chloride ions will enter the neuron,and the membrane potential will become more negative.
B)Chloride ions will enter the neuron,and the membrane potential will become more positive.
C)Chloride ions will exit the neuron,and the membrane potential will become more negative.
D)Chloride ions will exit the neuron,and the membrane potential will become more positive.

Question 57

The botulinum toxin inhibits the synaptic release of

A)acetylcholine.
B)epinephrine.
C)endorphin.
D)nitric oxide.
E)GABA.

Question 58

Nitric oxide is

A)a chemical that affects neuronal function but is not stored in presynaptic vesicles.
B)an amino acid that operates at inhibitory synapses in the brain.
C)a neuropeptide that might function as a natural analgesic.
D)the major inhibitory neurotransmitter of the human brain.

Question 59

Assume that a single IPSP has a negative magnitude of -0.5 mV at the axon hillock and that a single EPSP has a positive magnitude of +0.5 mV.For a neuron with an initial membrane potential of -70 mV,the net effect of the simultaneous arrival of six IPSPs and two EPSPs would be to move the membrane potential to

A)-72 mV.
B)-71 mV.
C)-70 mV.
D)-69 mV.
E)-68 mV.

Question 60

The heart rate decreases in response to the arrival of

A)acetylcholine.
B)epinephrine.
C)endorphin.
D)nitric oxide.
E)GABA.

Question 61

Which of the following could be an effective treatment for curare poisoning?

A)a drug that promotes acetylcholine reuptake into the presynaptic cells
B)a drug that removes acetylcholine receptors from the postsynaptic cell
C)a drug that inhibits acetylcholinesterase
D)a drug that activates acetylcholinesterase

Question 62

A common feature of action potentials is that they

A)cause the membrane to hyperpolarize and then depolarize.
B)can undergo temporal and spatial summation.
C)are triggered by a depolarization that reaches threshold.
D)move at the same speed along all axons.

Question 63

What happens when a resting neuron's membrane depolarizes?

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

Question 64

Researchers injected bark scorpion venom in mouse neurons (both a common house mouse and the southern grasshopper mouse)and measured the flow of sodium ions across the cell membrane.Their data are shown below. Based on these data,what effect do you think the venom is having on the grasshopper mouse?

A)The venom is blocking voltage-gated sodium channels.
B)The venom is blocking voltage-gated potassium channels.
C)The venom is opening voltage-gated sodium channels.
D)The venom is opening voltage-gated potassium channels.

Question 65

Please use the following information to answer the questions below.
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?

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

Question 66

Please use the following information to answer the questions 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?

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

Question 67

Researchers injected bark scorpion venom in mouse neurons (both a common house mouse and the southern grasshopper mouse)and measured how many action potentials were generated after the venom was introduced.Their data are shown below. Based on these data,what effect do you think the venom is having on the grasshopper mouse?

A)The venom is blocking voltage-gated sodium channels.
B)The venom is blocking voltage-gated potassium channels.
C)The venom is opening voltage-gated sodium channels.
D)The venom is opening voltage-gated potassium channels.

Question 68

Suppose a particular neurotransmitter causes an IPSP in postsynaptic cell X and an EPSP in postsynaptic cell Y.A likely explanation is that

A)the threshold value in the postsynaptic membrane is different for cell X and cell Y.
B)the axon of cell X is myelinated,but that of cell Y is not.
C)only cell Y produces an enzyme that terminates the activity of the neurotransmitter.
D)cells X and Y express different receptor molecules for this particular neurotransmitter.

Question 69

Please use the following information to answer the questions below.
The Arizona bark scorpion is the most venomous scorpion in North America,and its bite will cause extensive pain to a human that lasts up to three days.However,the southern grasshopper mouse is essentially immune to the sting of this scorpion and actually eats the scorpions as prey.Researchers have recently elucidated the neuronal reason for why the southern grasshopper mouse does not feel pain from bark scorpion venom.
The southern grasshopper mouse essentially does not feel pain when stung by the bark scorpion.What type of neuron is most likely affected in this scenario?

A)interneuron
B)motor neuron
C)sensory neuron
D)glial cells

Question 70

Where are neurotransmitter receptors located?

A)the nuclear membrane
B)the nodes of Ranvier
C)the postsynaptic membrane
D)synaptic vesicle membranes

Question 71

When mice feel pain on their bodies,they lick that part of their body.Researchers injected bark scorpion venom into the hind paws of the common house mouse and the southern grasshopper mouse;they also injected 0.9% saline (essentially salt water)as a control.The researchers then observed how long the mice licked their paws.Which of the data sets depicted below do you think the researchers collected?

A)A
B)B
C)C
D)D

Question 72

Figure 37.2
Suppose you are studying a toxin from a new species of poisonous snake,and you find that neurons exposed to the toxin can initiate action potentials,but they cannot send electrical signals to other neurons.What structure in Figure 37.2 is the toxin targeting?

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

Question 73

Please use the following information to answer the questions below.
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?

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

Question 74

Why are action potentials usually conducted in 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 75

Figure 37.2
Figure 37.2 shows many proteins in a neuron membrane.The first protein on the left is a sodium-potassium pump.What would happen if this protein became blocked and thus unable to function?

A)The cell's membrane potential would not change.
B)The cell would hyperpolarize.
C)The cell would depolarize.
D)The potassium and sodium gradients would be eliminated.

Question 76

Figure 37.2
Suppose you are designing a drug to prevent action potential generation in neurons without compromising the ability of a neuron to receive information.What structure in Figure 37.2 should the drug target?

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

Question 77

Which of the following is a direct result of depolarizing the presynaptic membrane of an axon terminal?

A)Voltage-gated calcium channels in the membrane open.
B)Synaptic vesicles fuse with the membrane.
C)Ligand-gated channels open,allowing neurotransmitters to enter the synaptic cleft.
D)An EPSP or IPSP is generated in the postsynaptic cell.