Question 1

Refer to the following graph of an action potential to answer the question.   Which Roman numeral in the graph indicates the falling phase of the action potential?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
A)  I 
B)  II 
C)  III 
D)  IV C

Question 2

Which of the following is a characteristic of an electrical synapse?

Accepted Answer

A)  gap junctions 
B)  acetylcholine 
C)  G protein-coupled receptors 
D)  summation 
A)  gap junctions 
B)  acetylcholine 
C)  G protein-coupled receptors 
D)  summation A

Question 3

An inhibitory postsynaptic potential (IPSP) will occur if a membrane is made more permeable to ________.

Accepted Answer

A)  potassium ions 
B)  sodium ions 
C)  ATP 
D)  all neurotransmitter molecules 
A)  potassium ions 
B)  sodium ions 
C)  ATP 
D)  all neurotransmitter molecules A

Question 4

Tetrodotoxin blocks voltage-gated sodium channels, and ouabain blocks sodium-potassium pumps. If you added both tetrodotoxin and ouabain to a solution containing neural tissue, what responses would you expect?

Accepted Answer

A)  immediate loss of resting potential 
B)  immediate loss of action potential with gradual shift of resting potential 
C)  slow decrease of resting potential and action potential amplitudes 
D)  No effect; the substances counteract each other. 
A)  immediate loss of resting potential 
B)  immediate loss of action potential with gradual shift of resting potential 
C)  slow decrease of resting potential and action potential amplitudes 
D)  No effect; the substances counteract each other.

Question 5

Which of the following is the most likely effect of applying the naturally occurring acetylcholinesterase inhibitor onchidal (produced by the mollusc Onchidella binneyi) to a neuromuscular junction?

Accepted Answer

A)  the muscle cell would not be able to contract 
B)  the muscle cell would receive constant stimulation 
C)  there would be a decrease in the frequency of action potentials 
D)  there would be no effect on the muscle cell function 
A)  the muscle cell would not be able to contract 
B)  the muscle cell would receive constant stimulation 
C)  there would be a decrease in the frequency of action potentials 
D)  there would be no effect on the muscle cell function

Question 6

The concentrations of sodium and potassium ions are very different inside and outside a neuron. What contributes to these differences?

Accepted Answer

A)  osmosis 
B)  diffusion of chloride ions 
C)  sodium-potassium pumps 
D)  exocytosis and endocytosis 
A)  osmosis 
B)  diffusion of chloride ions 
C)  sodium-potassium pumps 
D)  exocytosis and endocytosis

Question 7

A neurophysiologist is investigating reflexes in two different animals: a crab and a fish. Action potentials are found to pass more rapidly along the fish's neurons. What is a likely explanation?

Accepted Answer

A)  The fish's axons are smaller in diameter than the axons in the crab. 
B)  The fish's axons are myelinated. The crab's axons are not myelinated. 
C)  The fish's axons are not myelinated. The crab's axons are myelinated. 
D)  There is a higher percentage of ion channels in the axons of the crab compared with the percentage of ion channels in fish axons. 
A)  The fish's axons are smaller in diameter than the axons in the crab. 
B)  The fish's axons are myelinated. The crab's axons are not myelinated. 
C)  The fish's axons are not myelinated. The crab's axons are myelinated. 
D)  There is a higher percentage of ion channels in the axons of the crab compared with the percentage of ion channels in fish axons.

Question 8

What part of a neuron functions as the integrating center, where the membrane potential reflects the summed effect of all EPSPs and IPSPs?

Accepted Answer

A)  the nuclear membrane 
B)  region of the cell body where dendrites converge 
C)  the presynaptic terminals of the longest axon 
D)  the axon hillock 
A)  the nuclear membrane 
B)  region of the cell body where dendrites converge 
C)  the presynaptic terminals of the longest axon 
D)  the axon hillock

Question 9

What chemical affects neuronal function but is not stored in presynaptic vesicles?

Accepted Answer

A)  acetylcholine 
B)  epinephrine 
C)  nitric oxide 
D)  GABA 
A)  acetylcholine 
B)  epinephrine 
C)  nitric oxide 
D)  GABA

Question 10

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

Accepted Answer

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. 
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.

Question 11

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 becomes 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 becomes more negative than the outside.

Question 12

The botulinum toxin, which causes botulism, inhibits ________.

Accepted Answer

A)  presynaptic release of acetylcholine 
B)  absorption of acetylcholine 
C)  binding of acetylcholine on the postsynaptic membrane 
D)  synthesis of acetylcholine receptors 
A)  presynaptic release of acetylcholine 
B)  absorption of acetylcholine 
C)  binding of acetylcholine on the postsynaptic membrane 
D)  synthesis of acetylcholine receptors

Question 13

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

Accepted Answer

A)  the threshold value in the postsynaptic membrane for cell X is different from that for 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 
A)  the threshold value in the postsynaptic membrane for cell X is different from that for 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 14

What is the best indicator of the strength of a signal in a neuron?

Accepted Answer

A)  the rate at which action potentials are produced 
B)  the type of neurotransmitter involved in the signal 
C)  the types of ions involved in conveying the action potential 
D)  the degree of depolarization and repolarization of the membrane 
A)  the rate at which action potentials are produced 
B)  the type of neurotransmitter involved in the signal 
C)  the types of ions involved in conveying the action potential 
D)  the degree of depolarization and repolarization of the membrane

Question 15

If a pebble is tossed into a pond, it generates small ripples that decrease in size as the ripples move away from the point where the pebble struck the water. The decreasing size of the ripples as they move away from the initial splash is most like the way that signals spread ________.

Accepted Answer

A)  in a graded potential 
B)  in an action potential 
C)  during hyperpolarization 
D)  during depolarization 
A)  in a graded potential 
B)  in an action potential 
C)  during hyperpolarization 
D)  during depolarization

Question 16

Refer to the following graph of an action potential to answer the question.   Which Roman numeral in the graph indicates the minimum graded depolarization needed to operate the voltage-gated sodium and potassium channels?

Accepted Answer

A)  I 
B)  II 
C)  IV 
D)  V 
A)  I 
B)  II 
C)  IV 
D)  V

Question 17

The Nernst equation specifies the equilibrium potential for a particular ion. This equilibrium potential is a function of ________.

Accepted Answer

A)  hydrostatic pressure 
B)  the ion concentration gradient 
C)  the osmotic gradient 
D)  the temperature (thermal) gradient 
A)  hydrostatic pressure 
B)  the ion concentration gradient 
C)  the osmotic gradient 
D)  the temperature (thermal) gradient

Question 18

Which of the following is an example of a ligand-gated channel?

Accepted Answer

A)  electrical synapses in a vertebrate heart 
B)  acetylcholine receptors at a neuromuscular junction 
C)  the breakdown of acetylcholine in a neuromuscular synapse 
D)  the action of NO on smooth muscle 
A)  electrical synapses in a vertebrate heart 
B)  acetylcholine receptors at a neuromuscular junction 
C)  the breakdown of acetylcholine in a neuromuscular synapse 
D)  the action of NO on smooth muscle

Question 19

A common feature of action potentials is that they ________.

Accepted Answer

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 
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 20

Where are neurotransmitters released in a synapse?

Accepted Answer

A)  the presynaptic membrane 
B)  axon hillocks 
C)  cell bodies 
D)  the smooth endoplasmic reticulum 
A)  the presynaptic membrane 
B)  axon hillocks 
C)  cell bodies 
D)  the smooth endoplasmic reticulum

Exam 48: Electrical Signals in Animals

Refer to the following graph of an action potential to answer the question. Which Roman numeral in the graph indicates the falling phase of the action potential?

Which of the following is a characteristic of an electrical synapse?

An inhibitory postsynaptic potential (IPSP) will occur if a membrane is made more permeable to ________.

Tetrodotoxin blocks voltage-gated sodium channels, and ouabain blocks sodium-potassium pumps. If you added both tetrodotoxin and ouabain to a solution containing neural tissue, what responses would you expect?

Which of the following is the most likely effect of applying the naturally occurring acetylcholinesterase inhibitor onchidal (produced by the mollusc Onchidella binneyi) to a neuromuscular junction?

The concentrations of sodium and potassium ions are very different inside and outside a neuron. What contributes to these differences?

A neurophysiologist is investigating reflexes in two different animals: a crab and a fish. Action potentials are found to pass more rapidly along the fish's neurons. What is a likely explanation?

What part of a neuron functions as the integrating center, where the membrane potential reflects the summed effect of all EPSPs and IPSPs?

What chemical affects neuronal function but is not stored in presynaptic vesicles?

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

What happens when a resting neuron's membrane depolarizes?

The botulinum toxin, which causes botulism, inhibits ________.

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

What is the best indicator of the strength of a signal in a neuron?

If a pebble is tossed into a pond, it generates small ripples that decrease in size as the ripples move away from the point where the pebble struck the water. The decreasing size of the ripples as they move away from the initial splash is most like the way that signals spread ________.

Refer to the following graph of an action potential to answer the question. Which Roman numeral in the graph indicates the minimum graded depolarization needed to operate the voltage-gated sodium and potassium channels?

The Nernst equation specifies the equilibrium potential for a particular ion. This equilibrium potential is a function of ________.

Which of the following is an example of a ligand-gated channel?

A common feature of action potentials is that they ________.

Where are neurotransmitters released in a synapse?

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Carbon: the Basis of Molecular Diversity

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