Question 1

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

Question 2

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. 
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 3

Neurotransmitters categorized as inhibitory are expected to ________.

Accepted Answer

A)  act independently of their receptor proteins 
B)  close potassium channels 
C)  open sodium channels 
D)  hyperpolarize the membrane 
A)  act independently of their receptor proteins 
B)  close potassium channels 
C)  open sodium channels 
D)  hyperpolarize the membrane

Question 4

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. 
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 5

Most of the neurons in the human central nervous system are ________.

Accepted Answer

A)  sensory neurons 
B)  motor neurons 
C)  interneurons 
D)  peripheral neurons 
A)  sensory neurons 
B)  motor neurons 
C)  interneurons 
D)  peripheral neurons

Question 6

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

Question 7

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)  are open or closed depending on their type, and are specific as to which ion can traverse them 
D)  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)  are open or closed depending on their type, and are specific as to which ion can traverse them 
D)  open in response to stimuli, and then close simultaneously, in unison

Question 8

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. 
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 9

An example of ligand-gated ion channels is ________.

Accepted Answer

A)  the spreading of action potentials in the heart 
B)  acetylcholine receptors at the neuromuscular junction 
C)  cAMP-dependent protein kinases 
D)  action potentials on the axon 
A)  the spreading of action potentials in the heart 
B)  acetylcholine receptors at the neuromuscular junction 
C)  cAMP-dependent protein kinases 
D)  action potentials on the axon

Question 10

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. 
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.

Question 11

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 12

The "undershoot" phase of hyperpolarization is due to ________.

Accepted Answer

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 
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

Question 13

Where are neurotransmitter receptors located?

Accepted Answer

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

Question 14

Use the information in the table to answer the question.
$\begin{array}{l|l|l}
\text { Ion } & \begin{array}{l}
\text { Extracellular concentration } \
(\mathrm{mM})
\end{array} & \begin{array}{l}
\text { Intracellular concentration } \
(\mathrm{mM})
\end{array} \
\hline \mathrm{Na}^{+} & 300 & 50 \
\hline \mathrm{K}^{+} & 40 & 350
\end{array}$

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

Question 15

Pyrethroid insecticides prevent the voltage-gated sodium channels of insects from inactivating. Neurons that were exposed to pyrethroids would ________.

Accepted Answer

A)  become hyperpolarized during an action potential 
B)  not repolarize during an action potential 
C)  not be able to open potassium channels 
D)  not release neurotransmitter molecules 
A)  become hyperpolarized during an action potential 
B)  not repolarize during an action potential 
C)  not be able to open potassium channels 
D)  not release neurotransmitter molecules

Question 16

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 
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 17

Refer to the following graph of an action potential to answer the question.
 
The minimum graded depolarization needed to operate the voltage-gated sodium and potassium channels is indicated by the label ________.

Accepted Answer

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

Question 18

The "threshold" potential of a membrane is the ________.

Accepted Answer

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

Question 19

The fastest possible conduction velocity of action potentials is observed in ________.

Accepted Answer

A)  thin, unmyelinated neurons 
B)  thin, myelinated neurons 
C)  thick, unmyelinated neurons 
D)  thick, myelinated neurons 
A)  thin, unmyelinated neurons 
B)  thin, myelinated neurons 
C)  thick, unmyelinated neurons 
D)  thick, myelinated neurons

Question 20

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. 
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.

Exam 48: Neurons, Synapses, and Signaling

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

Why are action potentials usually conducted in one direction?

Neurotransmitters categorized as inhibitory are expected to ________.

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

Most of the neurons in the human central nervous system are ________.

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 ________.

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

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?

An example of ligand-gated ion channels is ________.

Which of the following statements about action potentials is correct?

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

The "undershoot" phase of hyperpolarization is due to ________.

Where are neurotransmitter receptors located?

Use the information in the table to answer the question. Ion Extracellular concentration () Intracellular concentration () 300 50 40 350 Calculate the equilibrium potential for potassium. Assume a temperature of 37°C.

Pyrethroid insecticides prevent the voltage-gated sodium channels of insects from inactivating. Neurons that were exposed to pyrethroids would ________.

Refer to the following graph of an action potential to answer the question. The minimum graded depolarization needed to operate the voltage-gated sodium and potassium channels is indicated by the label ________.

The "threshold" potential of a membrane is the ________.

The fastest possible conduction velocity of action potentials is observed in ________.

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?

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