Question 1

Which of the following ions is most likely to cross the plasma membrane of a resting neuron?

Accepted Answer

A)   K⁺
B)   Na⁺
C)   Ca2+
D)   Cl-E) A) and B)
F) A) and C)

Question 2

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.E) B) and C)
F) C) and D)

Question 3

Which of the following statements about action potentials is correct?

Accepted Answer

A)   Action potentials for a given neuron vary in magnitude.
B)   Action potentials for a given neuron vary in duration.
C)   Action potentials are propagated down the length of the axon.
D)   Movement of ions during the action potential occurs mostly through the sodium pump.E) All of the above
F) A) and B)

Question 4

In a simple synapse, neurotransmitter chemicals are released by ________.

Accepted Answer

A)   the presynaptic membrane
B)   axon hillocks
C)   cell bodies
D)   ducts on the smooth endoplasmic reticulumE) A) and C)
F) A) and B)

Question 5

The motor (somatic nervous)  system can alter the activities of its targets, the skeletal muscle fibres, because ________.

Accepted Answer

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)   it is connected to the internal neural network of the musclesE) A) and C)
F) All of the above

Question 6

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 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.E) None of the above
F) A) and B)

Question 7

A graded hyperpolarisation of a membrane can be induced by ________.

Accepted Answer

A)   increasing its membrane's permeability to Na⁺
B)   decreasing its membrane's permeability to Cl-
C)   increasing its membrane's permeability to Ca⁺⁺
D)   increasing its membrane's permeability to K⁺E) None of the above
F) A) and B)

Question 8

What would probably happen if a long neuron had one continuous myelin sheath down the length of the axon with no nodes of Ranvier?

Accepted Answer

A)   The action potential would be propagated nearly instantaneously to the synapse.
B)   There could be no action potential generated at the axon hillock.
C)   The signal would fade because it is not renewed by the opening of more sodium channels.
D)   Only potassium could move across the membrane, but not sodium.E) C) and D)
F) B) and D)

Question 9

At the neuromuscular junction, the neurotransmitter acetylcholine (ACh)  is degraded by acetylcholinesterase. If a neurophysiologist applies the naturally occurring acetylcholinesterase inhibitor, onchidal (produced by the mollusc Onchidella binneyi) , to a synapse, what would you expect to happen?

Accepted Answer

A)   paralysis of muscle tissue
B)   convulsions due to constant muscle stimulation
C)   decrease in the frequency of action potentials
D)   no effectE) None of the above
F) B) and C)

Question 10

What happens if twice as many inhibitory postsynaptic potentials (IPSPs)  as excitatory postsynaptic potentials (EPSPs)  arrive in close proximity at a postsynaptic neuron?

Accepted Answer

A)   A stronger action potential results.
B)   A weaker action potential results.
C)   No action potential results.
D)   Many action potentials result.E) A) and B)
F) None of the above

Question 11

Refer to the following graph of an action potential to answer the question.  The membrane potential is closest to the equilibrium potential for potassium at label ________.

Accepted Answer

A)   A
B)   B
C)   C
D)   D Disallow randomisationE) A) and B)
F) A) and C)

Question 12

In a simple synapse, neurotransmitter chemicals are received by ________.

Accepted Answer

A)   the presynaptic membrane
B)   dendrites
C)   axon hillocks
D)   cell bodiesE) A) and C)
F) A) and B)

Question 13

Refer to the following graph of an action potential to answer the question.  At label ________, the cell is not hyperpolarised; however, repolarisation is in progress, as the sodium channels are inactivated or becoming inactivated, and many potassium channels have opened.

Accepted Answer

A)   B
B)   C
C)   D
D)   E Disallow randomisationE) A) and B)
F) B) and D)

Question 14

What happens when a resting neuron's membrane depolarises?

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.E) None of the above
F) B) and D)

Question 15

Conduction and refractory periods (states)  are typical of ________.

Accepted Answer

A)   action potentials
B)   graded hyperpolarisations
C)   excitatory postsynaptic potentials
D)   threshold potentialsE) A) and D)
F) B) and C)

Question 16

A neurophysiologist is investigating nerve 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 the most likely explanation?

Accepted Answer

A)   The fish's axons are smaller in diameter; small axons transmit action potentials faster than large axons do.
B)   Unlike the crab, the fish's axons are wrapped in myelin.
C)   There are more ion channels in the axons of the crab compared with fish axons.
D)   Unlike the crab, the fish's axons are wrapped in myelin, and the fish's axons are smaller in diameter; small axons transmit action potentials faster than large axons do.E) All of the above
F) A) and B)

Question 17

Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium/potassium channel and opens it. This is an example of ________.

Accepted Answer

A)   a voltage-gated channel
B)   a ligand-gated channel
C)   a second-messenger-gated channel
D)   a chemical that inhibits action potentialsE) A) and B)
F) B) and D)

Question 18

An inhibitory postsynaptic potential (IPSP)  occurs in a membrane made more permeable to ________.

Accepted Answer

A)   potassium ions
B)   sodium ions
C)   ATP
D)   all neurotransmitter moleculesE) A) and D)
F) All of the above

Question 19

The activity of acetylcholine in a synapse is terminated by its ________.

Accepted Answer

A)   diffusion across the presynaptic membrane
B)   active transport across the postsynaptic membrane
C)   diffusion across the postsynaptic membrane
D)   degradation on the postsynaptic membraneE) A) and D)
F) A) and C)

Question 20

Neurotransmitters are released from axon terminals via ________.

Accepted Answer

A)   osmosis
B)   active transport
C)   diffusion
D)   exocytosisE) A) and B)
F) C) and D)

Exam 48: Neurons, Synapses, and Signalling

What would probably happen if a long neuron had one continuous myelin sheath down the length of the axon with no nodes of Ranvier?

Correct AnswerverifiedShow Answer

Refer to the following graph of an action potential to answer the question. The membrane potential is closest to the equilibrium potential for potassium at label ________.

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium/potassium channel and opens it. This is an example of ________.

Correct AnswerverifiedShow Answer

What happens when a resting neuron's membrane depolarises?

Correct AnswerverifiedShow Answer

The motor (somatic nervous) system can alter the activities of its targets, the skeletal muscle fibres, because ________.

Correct AnswerverifiedShow Answer

At the neuromuscular junction, the neurotransmitter acetylcholine (ACh) is degraded by acetylcholinesterase. If a neurophysiologist applies the naturally occurring acetylcholinesterase inhibitor, onchidal (produced by the mollusc Onchidella binneyi) , to a synapse, what would you expect to happen?

Correct AnswerverifiedShow Answer

Which of the following ions is most likely to cross the plasma membrane of a resting neuron?

Correct AnswerverifiedShow Answer

Refer to the following graph of an action potential to answer the question. At label ________, the cell is not hyperpolarised; however, repolarisation is in progress, as the sodium channels are inactivated or becoming inactivated, and many potassium channels have opened.

Correct AnswerverifiedShow Answer

In a simple synapse, neurotransmitter chemicals are received by ________.

Correct AnswerverifiedShow Answer

Conduction and refractory periods (states) are typical of ________.

Correct AnswerverifiedShow Answer

Which of the following statements about action potentials is correct?

Correct AnswerverifiedShow Answer

An inhibitory postsynaptic potential (IPSP) occurs in a membrane made more permeable to ________.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

The activity of acetylcholine in a synapse is terminated by its ________.

Correct AnswerverifiedShow Answer

In a simple synapse, neurotransmitter chemicals are released by ________.

Correct AnswerverifiedShow Answer

A neurophysiologist is investigating nerve 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 the most likely explanation?

Correct AnswerverifiedShow Answer

What happens if twice as many inhibitory postsynaptic potentials (IPSPs) as excitatory postsynaptic potentials (EPSPs) arrive in close proximity at a postsynaptic neuron?

Correct AnswerverifiedShow Answer

Neurotransmitters are released from axon terminals via ________.

Correct AnswerverifiedShow Answer

A graded hyperpolarisation of a membrane can be induced by ________.

Correct AnswerverifiedShow Answer

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