Question 1

How could you increase the magnitude of excitatory postsynaptic potentials (EPSPs) generated at a synapse?

Accepted Answer

A)   Increase sodium-potassium pump activity.
B)   Increase K⁺ permeability.
C)   Increase Na⁺ permeability.
D)   All of the listed responses are correct. C

Question 2

Use the information in the table to answer the question.

Calculate the equilibrium potential for sodium. Assume a temperature of 37°C.

Accepted Answer

A)   +48.2 mV
B)   0.0 mV
C)   -58.4 mV
D)   -80.0 mV A

Question 3

In multiple sclerosis, the myelin sheaths around the axons of the brain and spinal cord are damaged and demyelination results. How does this disease manifest at the level of the action potential?
I.Action potentials move in the opposite direction on the axon.
II.Action potentials move more slowly along the axon.
III.No action potentials are transmitted.

Accepted Answer

A)   only I
B)   only II
C)   only III
D)   only II and III B

Question 4

If excitatory postsynaptic potentials (EPSPs) are produced nearly simultaneously through two different synapses on the same postsynaptic neuron, the EPSPs can also add together creating ________.

Accepted Answer

A)   a temporal summation
B)   a spatial summation
C)   a tetanus
D)   the refractory state

Question 5

A researcher uses the chemical inhibitor cyanide to reduce ATP production in a neuron. What would be one effect of preventing ATP production?

Accepted Answer

A)   The sodium and potassium channels would all be closed.
B)   The membrane would become more permeable to sodium.
C)   Disruption to the normal "resting" distribution of potassium and sodium ions.
D)   A physical breakdown of the plasma membrane would occur.

Question 6

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, using an electronic probe, then ________.

Accepted Answer

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

Question 7

Refer to the following graph of an action potential to answer the question.

The membrane's permeability to sodium ions is greatest at label ________.

Accepted Answer

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

Question 8

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 effect

Question 9

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.

Question 10

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

Accepted Answer

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

Question 11

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 molecules

Question 12

If you experimentally increase the concentration of K⁺ inside a cell while maintaining other ion concentrations as they were, what would happen to the cell's membrane potential?

Accepted Answer

A)   The membrane potential would become more negative.
B)   The membrane potential would become less negative.
C)   The membrane potential would remain the same.
D)   The membrane potential would first become more negative and then less negative.

Question 13

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

Accepted Answer

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

Question 14

Neurotransmitters are released from axon terminals via ________.

Accepted Answer

A)   osmosis
B)   active transport
C)   diffusion
D)   exocytosis

Question 15

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

Question 16

The concentrations of ions are very different inside and outside a nerve cell due to ________.

Accepted Answer

A)   osmosis
B)   diffusion
C)   sodium-potassium pumps
D)   symports and antiports

Question 17

Use the information in the table to answer the question.

Calculate the equilibrium potential for potassium. Assume a temperature of 37°C.

Accepted Answer

A)   +48.2 mV
B)   0.0 mV
C)   -58.4 mV
D)   -80.0 mV

Question 18

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 potentials

Question 19

Why are action potentials usually conducted in one direction?

Accepted Answer

A)   Ions can flow along the axon in only one direction.
B)   The brief refractory period prevents reopening of voltage-gated Na⁺ channels.
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 20

The botulinum toxin, which causes botulism, reduces the synaptic release of ________.

Accepted Answer

A)   acetylcholine
B)   endorphin
C)   nitric oxide
D)   gamma-aminobutyric acid (GAB
A)

Exam 48: Neurons, Synapses, and Signaling