A&P1 Chapter 11 and 9 matching

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The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.

A. K+; Na+

B. K+; Cl-

C. Na+; Cl-

D. Na+; K+

A. K+; Na+

During depolarization, which gradient(s) move(s) Na+ into the cell?

A. only the chemical gradient

B. both the electrical and chemical gradients

C. only the electrical gradient

D. Na+ does not move into the cell. Na+ moves out of the cell.

B. both the electrical and chemical gradients

What is the value for the resting membrane potential for most neurons?

A. +30 mV

B. -90 mV

C. -70 mV

C. -70 mV

The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?

A. K+ is pumped out of the cell and Na+ is pumped into the cell.

B. Both Na+ and K+ are pumped out of the cell.

C. Both Na+ and K+ are pumped into the cell.

D. Na+ is pumped out of the cell and K+ is pumped into the cell.

D. Na+ is pumped out of the cell and K+ is pumped into the cell.

The concentrations of which two ions are highest outside the cell.

A. K+ and A- (negatively charged proteins)

B. Na+ and A- (negatively charged proteins)

C. K+ and Cl-

D. Na+ and Cl-

D. Na+ and Cl-

Where in the neuron is an action potential initially generated?

A. anywhere on the axon

B. axon hillock

C. soma and dendrites

B. axon hillock

The depolarization phase of an action potential results from the opening of which channels?

A. chemically gated K+ channels

B. voltage-gated Na+ channels

C. voltage-gated K+ channels

D. chemically gated Na+ channels

B. voltage-gated Na+ channels

The repolarization phase of an action potential results from __________.

A. the closing of voltage-gated K+ channels

B. the opening of voltage-gated K+ channels

C. the closing of voltage-gated Na+ channels

D .the opening of voltage-gated Na+ channels

B. the opening of voltage-gated K+ channels

Hyperpolarization results from __________.

A. slow closing of voltage-gated Na+ channels

B. slow closing of voltage-gated K+ channels

C. fast closing of voltage-gated K+ channels

B. slow closing of voltage-gated K+ channels

What is the magnitude (amplitude) of an action potential?

A. 100 mV

B. 70 mV

C. 30 mV

A. 100 mV

How is an action potential propagated along an axon?

A. An efflux of potassium from the current action potential depolarizes the adjacent area.

B. An influx of sodium ions from the current action potential depolarizes the adjacent area.

C. Stimuli from the graded (local) potentials from the soma and dendrites depolarize the entire axon.

B. An influx of sodium ions from the current action potential depolarizes the adjacent area.

Why does the action potential only move away from the cell body?

A. The flow of the sodium ions only goes in one direction—away from the cell body

B. The areas that have had the action potential are refractory to a new action potential.

B. The areas that have had the action potential are refractory to a new action potential.

The velocity of the action potential is fastest in which of the following axons?

A. a large unmyelinated axon

B. a small myelinated axon

C. a small unmyelinated axon

B. a small myelinated axon

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?

A. Action potential

B. Positive membrane potential

C. Resting membrane potential (RMP)

D. Threshold potential

C. Resting membrane potential (RMP)

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

A. Sodium-potassium ATPases

B. Leak channels

C. Voltage-gated channels

D. Ligand-gated channels

B. Leak channels

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?

A. The outside surface of the plasma membrane is much more negatively charged than the inside surface.

B. The inside surface of the plasma membrane is much more negatively charged than the outside surface.

C. The inside surface of the plasma membrane is much more positively charged than the inside surface.

D. There is no electrical potential difference between the inside and the outside surfaces of the plasma membrane.

B. The inside surface of the plasma membrane is much more negatively charged than the outside surface.

The plasma membrane is much more permeable to K+ than to Na+. Why?

A. There are many more K+ leak channels than Na+ leak channels in the plasma membrane.

B. Ligand-gated cation channels favor a greater influx of Na+ than K+.

C. There are many more voltage-gated K+ channels than voltage-gated Na+ channels.

D. The Na+-K+ pumps transport more K+ into cells than Na+ out of cells.

A. There are many more K+ leak channels than Na+ leak channels in the plasma membrane.

The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.

A. The presence of concentration gradients and leak channels

B. The presence of concentration gradients and voltage-gated channels

C. The presence of a resting membrane potential and leak channels

D. The presence of concentration gradients and Na+-K+ pumps

A. The presence of concentration gradients and leak channels

What prevents the Na+ and K+ gradients from dissipating?

A. Na+-K+ ATPase

B. H+-K+ ATPase

C. Na+ and K+ leaks

D. Na+ cotransporter

A. Na+-K+ ATPase

Where do most action potentials originate?

A. Axon terminal

B. Nodes of Ranvier

C. Initial segment

D. Cell body

C. Initial segment

What opens first in response to a threshold stimulus?

A. Ligand-gated Cl- channels

B. Voltage-gated K+ channels

C. Ligand-gated cation channels

D. Voltage-gated Na+ channels

D. Voltage-gated Na+ channels

What characterizes depolarization, the first phase of the action potential?

A. The membrane potential changes from a negative value to a positive value.

B. The membrane potential reaches a threshold value and returns to the resting state.

C. The membrane potential changes to a much more negative value.

D. The membrane potential changes to a less negative (but not a positive) value.

A. The membrane potential changes from a negative value to a positive value

What characterizes repolarization, the second phase of the action potential?

A. Before the membrane has a chance to reach a positive voltage, it repolarizes to its negative resting value of approximately -70 mV.

B. Once the membrane depolarizes to a threshold value of approximately -55 mV, it repolarizes to its resting value of -70 mV.

C. Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.

D. As the membrane repolarizes to a negative value, it goes beyond the resting state to a value of -80 mV.

C. Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.

What event triggers the generation of an action potential?

a. The membrane potential must return to its resting value of -70 mV from the hyperpolarized value of -80 mV.

B. The membrane potential must hyperpolarize from the resting voltage of -70 mV to the more negative value of -80 mV.

C. The membrane potential must depolarize from the resting voltage of -70 mV to its peak value of +30 mV.

D. The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

D. The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

What is the first change to occur in response to a threshold stimulus?

A. Voltage-gated K+ channels change shape, and their activation gates open.

B. Voltage-gated Ca2+ channels change shape, and their activation gates open.

C. Voltage-gated Na+ channels change shape, and their activation gates open.

D. Voltage-gated Na+ channels change shape, and their inactivation gates close.

C. Voltage-gated Na+ channels change shape, and their activation gates open.

What type of conduction takes place in unmyelinated axons?

A. Electrical conduction

B. Saltatory conduction

C. Synaptic transmission

D. Continuous conduction

D. Continuous conduction

An action potential is self-regenerating because __________.

A. repolarizing currents established by the efflux of Na+‎ flow down the axon and trigger an action potential at the next segment

B. repolarizing currents established by the efflux of K+‎ flow down the axon and trigger an action potential at the next segment

C. depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment

D. depolarizing currents established by the influx of K+‎ flow down the axon and trigger an action potential at the next segment

C. depolarizing currents established by the influx of Na+‎ flow down the axon and trigger an action potential at the next segment

Why does regeneration of the action potential occur in one direction, rather than in two directions?

A. The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential.

B. The inactivation gates of voltage-gated K+‎ channels close in the node, or segment, that has just fired an action potential.

C. The activation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just depolarized.

D. The activation gates of voltage-gated K+‎ channels open in the node, or segment, that has just depolarized.

A. The inactivation gates of voltage-gated Na+‎ channels close in the node, or segment, that has just fired an action potential.

What is the function of the myelin sheath?

A. The myelin sheath increases the insulation along the entire length of the axon.

B. The myelin sheath decreases the speed of action potential conduction from the initial segment to the axon terminals.

C. The myelin sheath decreases the resistance of the axonal membrane to the flow of charge.

D. The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

D. The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.

What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?

A. Activation gates of voltage-gated Na+‎ channels close, while inactivation gates of voltage-gated K+‎ channels open.

B. Activation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

C. Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

D. Inactivation gates of voltage-gated Na+‎ channels close, while inactivation gates of voltage-gated K+‎ channels open.

C. Inactivation gates of voltage-gated Na+‎ channels close, while activation gates of voltage-gated K+‎ channels open.

In which type of axon will velocity of action potential conduction be the fastest?

A. Unmyelinated axons of the shortest length

B. Myelinated axons with the largest diameter

C. Myelinated axons with the smallest diameters

D. Unmyelinated axons with the largest diameter

B. Myelinated axons with the largest diameter

During the action potential of a neuron, which ion is primarily crossing the membrane during the depolarization phase, and in which direction is the ion moving?

A. Na+ is entering the cell.

B. K+ is exiting the cell.

C. Na+ is exiting the cell.

D. K+ is entering the cell.

A. Na+ is entering the cell.

During what part of the action potential do voltage-gated Na+ channels begin to inactivate (their inactivation gates close)?

A. at the end of the repolarization phase, as the membrane potential briefly passes its resting value

B. at the end of the hyperpolarization phase of an action potential, as the membrane potential returns to its resting value

C. at the end of the depolarization phase, as the membrane potential approaches its peak value

D. at the beginning of an action potential, as the membrane potential reaches threshold

C. at the end of the depolarization phase, as the membrane potential approaches its peak value

The repolarization phase of the action potential, where voltage becomes more negative after the +30mV peak, is caused primarily by __________.

A. K+ ions leaving the cell through voltage-gated channels

B. Na+ ions leaving the cell through voltage-gated channels

C. K+ ions entering the cell through voltage-gated channels

D. Na+ ions transported out of the cell by the Na+-K+ pump

A. K+ ions leaving the cell through voltage-gated channels

During an action potential, hyperpolarization beyond (more negative to) the resting membrane potential is primarily due to __________.

A. K+ ions diffusing through leakage channels

B. Na+ diffusing through voltage-gated channels

C. K+ ions diffusing through voltage-gated channels

D. Na+-K+ pump activity

C. K+ ions diffusing through voltage-gated channels

During the hyperpolarization phase of the action potential, when the membrane potential is more negative than the resting membrane potential, what happens to voltage-gated ion channels?

A. K+ channels close. Na+ channels open.

B. K+ channels close. Na+ channels go from an inactivated state to a closed state.

C. K+ channels open. Na+ channels inactivate.

D. K+ channels close. Leakage channels open.

B. K+ channels close. Na+ channels go from an inactivated state to a closed state.

Tetraethylammonium (TEA) blocks voltage-gated K+ channels such that K+ cannot pass even when the channels are open. However, TEA leaves K+ leakage channels largely unaffected. How would you expect the action potential to change if you treated a neuron with TEA?

A. The membrane would depolarize as usual but then stay at that depolarized voltage (about +30 mV).

B. The action potential would depolarize as usual, but the repolarization phase would take longer, causing the action potential to be more broad in time.

C. The membrane would depolarize and repolarize as usual, but no hyperpolarization beyond (more negative to) the resting membrane potential would occur.

D. The action potential would fail. Once the voltage reached threshold, it would return to the resting membrane potential.

B. The action potential would depolarize as usual, but the repolarization phase would take longer, causing the action potential to be more broad in time.

The diffusion of what ion, across the neuronal membrane, is responsible for the local currents that depolarize regions of the axon to threshold?

A. voltage-gated Na+ (sodium) channels

B. K+ (potassium)

C. Na+ (sodium)

D. Ca2+ (calcium)

C. Na+ (sodium)

An action potential in one segment of axon causes adjacent sections of axon membrane to reach threshold through what mechanism?

A. K+ ions diffusing through voltage-gated channels

B. the generation of local currents

C. neurotransmitters causing chemically gated channels to open

D .Na+ ions diffusing across the membrane through leakage channels

B. the generation of local currents

During action potential propagation in an unmyelinated axon, why doesn’t the action potential suddenly "double back" and start propagating in the opposite direction?

A. The previous axonal segment is in the refractory period.

B. Positive charges only move in one direction after they enter the cell.

C. New action potential generation near the soma repels previously generated action potentials, causing them to always propagate away from the soma.

D. The extracellular sodium concentration is too low around the previous axonal segment for an action potential to be (re)generated.

A. The previous axonal segment is in the refractory period.

In a myelinated axon, how do the nodes of Ranvier differ from other segments of the same axon?

A. The nodes are more permeable to ions.

B. The nodes are less numerous.

C. The nodes are wrapped in myelin.

D. The nodes are longer segments of the axon.

A. The nodes are more permeable to ions.

Where are action potentials regenerated as they propagate along a myelinated axon?

A. at the nodes of Ranvier

B. at the axon hillock

C. at every segment of the axon

D. at the myelinated segments

A. at the nodes of Ranvier

How do action potential propagation speeds compare in myelinated and unmyelinated axons?

A. Propagation in unmyelinated axons is faster over short distances, but propagation is faster in myelinated axons over long distances.

B. Propagation is faster in myelinated axons.

C. Propagation is faster in unmyelinated axons.

D. Propagation speeds are similar in both axon types.

B. Propagation is faster in myelinated axons.

The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.

A. continuous conduction

B. saltatory conduction

C. local conduction

D. myelinated conduction

B. saltatory conduction

The myelin on myelinated neurons can be degraded or destroyed in diseases such as multiple sclerosis-a process called demyelination. If a myelinated neuron was affected by demyelination, how would this affect action potentials in that neuron?

A. Initial generation of action potentials would be more difficult.

B. The speed of action potential propagation would be faster.

C. The speed of action potential propagation would be slower.

D. Action potentials would propagate in both directions along the axon.

C. The speed of action potential propagation would be slower.

Which of the following best describes the Na+ and K+ concentrations across a neuron’s plasma membrane?

A. Both Na+ and K+ concentrations are higher inside the cell compared to outside.

B. The Na+ concentration is higher inside the cell compared to outside. The K+ concentration is higher outside the cell compared to inside.

C. Both Na+ and K+ concentrations are higher outside the cell compared to inside.

D. The Na+ concentration is higher outside the cell compared to inside. The K+ concentration is higher inside the cell compared to outside.

D. The Na+ concentration is higher outside the cell compared to inside. The K+ concentration is higher inside the cell compared to outside.

What is the major role of the Na+-K+ pump in maintaining the resting membrane potential?

A. hydrolyzing ATP

B. maintaining the concentration gradients for Na+ and K+ across the cell membrane

C. making the membrane potential negative by moving more Na+ ions out of the cell than K+ ions into the cell

D. permitting Na+ and K+ ions to diffuse across the plasma membrane

B. maintaining the concentration gradients for Na+ and K+ across the cell membrane

Which of the following is the clearest example of a neuronal membrane’s selective permeability?

A. The concentration gradient for Na+ ions is inward, but the concentration gradient for K+ ions is outward.

B. The Na+-K+ pump only transports Na+ and K+ ions.

C. K+ ions can diffuse across the membrane more easily than Na+ ions.

D. Diffusion of K+ ions out of the neuron causes the membrane potential to become more negative.

C. K+ ions can diffuse across the membrane more easily than Na+ ions.

Which of the following would increase the membrane permeability to K+?

A. more K+ leakage channels

B. more negative membrane potential

C. more Na+ leakage channels

D. a greater concentration gradient for K+

A. more K+ leakage channels

Suppose a drug is developed that blocks K+ leakage channels. The drug prevents ions from passing through those channels. If this drug was applied to a neuron, what would be the most immediate effect on that neuron?

A. The resting membrane potential would become less negative (more positive).

B. The concentration gradient for K+ would decrease.

C. The resting membrane potential would become more negative.

D. The concentration gradient for Na+ would decrease.

A. The resting membrane potential would become less negative (more positive).

Imagine you changed the concentration of K+ outside a neuron such that the resting membrane potential changed to -80 mV (from the normal resting value of -70 mV). What have you changed?

A. the electrical gradient for K+

B. the concentration gradient for K+

C. the electrical gradients and concentration gradients for both Na+ and K+.

D. the electrical gradient for K+ and the concentration gradient for K+

D. the electrical gradient for K+ and the concentration gradient for K+

What is the electrochemical gradient of an ion?

A. the direction an ion would tend to diffuse based on the membrane potential

B. the difference between the inside and outside concentrations of that ion

C. the sum of the electrical and concentration gradients for that ion

D. the membrane potential at which the electrical gradient and concentration gradient for that ion are equal in magnitude, but opposite in direction

C. the sum of the electrical and concentration gradients for that ion

Hypothetically, what would be the most immediate effect of doubling the number of Na+ leakage channels in the plasma membrane?

A. The resting membrane potential would become more negative.

B. The inward concentration gradient for Na+ would become larger.

C. The resting membrane potential would become less negative (more positive).

D. The outward concentration gradient for K+ would become smaller.

C. The resting membrane potential would become less negative (more positive).

What does 0 mV on the Y-axis of an action potential tracing represent?

A. The cell’s membrane is at equilibrium.

B. Ions are no longer moving across the membrane.

C. The cell is both depolarized and repolarized.

D. The cell is at its resting membrane potential.

A. The cell’s membrane is at equilibrium.

Which statement best characterizes a K+ leak channel?

A. Trans-membrane channels that use energy to allow the movement of K+ across the membrane.

B. Trans-membrane protein channels that are always open to allow K+ to cross the membrane without the additional input of energy.

C. Chemically gated K+ channels that open and close according to the binding of other molecules.

D. Common trans-membrane channels are always open for any ion to move through in the presence of K+

B. Trans-membrane protein channels that are always open to allow K+ to cross the membrane without the additional input of energy.

Assume you have a membrane with only potassium leak channels. The RMP is -90mV. Predict the RMP if we add Na+ leak channels.
The most likely RMP value of Na+ is __________.

A. -50 mV

B. +90 mV

C. +70 mV

D. -90 mV

E. -70 mV

E. -70 mV

Imagine that the cell membrane from the previous problem becomes more permeable to Na+. Predict how this will affect the RMP.

A. The RMP will be more negative.

B. The RMP will be unaffected.

C. The RMP will be more positive.

D. The RMP will be zero.

C. The RMP will be more positive.

Complete the following sentence. The operation of the Na+−K+ ATPase pump __________.

A. moves 2 Na+ to the ECF and 3 K+ to the cytoplasm

B. moves 3 Na+ to the ECF and 2 K+ to the cytoplasm

C. releases 1 Na+ to the ECF and 1 K+ to the cytoplasm

D. releases 3 K+ to the ECF

B. moves 3 Na+ to the ECF and 2 K+ to the cytoplasm

You are going to record RMP from a cell using an electrode. You place your electrode and record a resting membrane potential every millisecond. You record an initial value of -70mV; however, over time you notice that your recordings become more and more positive until the RMP reaches 0mV. Assuming that Na+ and K+ are the major determinants of RMP in this cell, which of the following could best explain your results?

A. The cell’s Na+−K+ ATPase pumps have stopped functioning.

B. The cell is becoming depleted of K+.

C. The cell’s Na+ leak channels have stopped functioning.

D. The cell’s K+ leak channels have stopped functioning.

E. The cell is becoming depleted of Na+.

A. The cell’s Na+−K+ ATPase pumps have stopped functioning.

Cl− is a common negatively charged extracellular ion. Predict the effect on the RMP if many Cl− gated channels are suddenly opened.

A. A more negative RMP would result.

B. There would be no change in the RMP.

C. The RMP would become more positive.

D. The membrane would become hypopolarized or have less charge separation across the membrane.

A. A more negative RMP would result.

The generation of an action potential in a neuron requires the presence what type of membrane channels?
Select the best answer.

A. chemically gated channels

B. voltage-gated channels

C. leakage channels

D. membrane channels are not required

B. voltage-gated channels

Saltatory propagation occurs in _________ axons, in which action potentials _________.
Select the best answer.

A. myelinated; move from one node of Ranvier to another

B. myelinated; move continuously along the axon toward the axon hillock

C. unmyelinated; spread by depolarizing the adjacent region of the axon membrane

D. unmyelinated; move from one node of Ranvier to another

A. myelinated; move from one node of Ranvier to another

In a synapse, neurotransmitters are stored in vesicles located in the __________.

A. presynaptic neuron

B. postsynaptic neuron

C. synaptic cleft

A. presynaptic neuron

An action potential releases neurotransmitter from a neuron by opening which of the following channels?

A. voltage-gated Na+ channels

B. voltage-gated Ca2+ channels

C. chemically gated Ca2+ channels

D. voltage-gated K+ channels

B. voltage-gated Ca2+ channels

Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.

A. voltage-gated; postsynaptic

B. chemically gated; presynaptic

C. chemically gated; postsynaptic

D. voltage-gated; presynaptic

C. chemically gated; postsynaptic

Binding of the neurotransmitter to its receptor causes the membrane to __________.

A. hyperpolarize

B. depolarize

C. either depolarize or hyperpolarize

C. either depolarize or hyperpolarize

The mechanism by which the neurotransmitter is returned to a presynaptic neuron’s axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?

A. glutamate

B. acetylcholine

B. acetylcholine

The small space between the sending neuron and the receiving neuron is the

A. neurotransmitter.

B. synaptic cleft.

C. vesicle.

C. synaptic terminal.

D. calcium channel.

B. synaptic cleft.

A molecule that carries information across a synaptic cleft is a

A. synapse.

B. neurotransmitter.

C. receiving neuron.

D. synaptic cleft.

E. sending neuron.

B. neurotransmitter.

When calcium ions enter the synaptic terminal,

A. the inside of the receiving neuron becomes more positive.

B. the inside of the receiving neuron becomes more negative.

C. neurotransmitter molecules are quickly removed from the synaptic cleft.

D. they cause an action potential in the sending neuron.

E. they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

E. they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

A. ion channels in the plasma membrane of the sending neuron open.

B. ion channels in the plasma membrane of the receiving neuron open.

C. the receiving neuron becomes more positive inside.

D. vesicles in the synaptic terminal fuse to the plasma membrane of the sending neuron.

E. the receiving neuron becomes more negative inside.

B. ion channels in the plasma membrane of the receiving neuron open.

If a signal from a sending neuron makes the receiving neuron more negative inside,

A. the receiving neuron is less likely to generate an action potential.

B. the sending neuron becomes more negative inside.

C. the receiving neuron is more likely to generate an action potential.

D. the sending neuron becomes more positive inside.

E. the receiving neuron immediately generates an action potential.

A. the receiving neuron is less likely to generate an action potential.

Which of the following best characterizes depolarization?

A. small consecutive steps of Na+ exit from cytoplasm into extracellular fluid

B. mass movement of Na+ into the axon cytoplasm from the cell body to the terminal

C. small consecutive steps of Na+ penetration into the axon along its length

D. small consecutive steps of K+ entering the cytoplasm

C. small consecutive steps of Na+ penetration into the axon along its length

When an action potential arrives at the end of the axon terminal, a series of events take place that result in the release of neurotransmitter from the presynaptic axon. Select the answer that correctly describes the primary stimulus for vesicles to move towards the cell membrane and eventually release their contents.

A. voltage-gated channels open, and K+ exits to the extracellular fluid, decreasing intracellular K+.

B. voltage-gated membrane channels open, and Ca+2 enters the cytoplasm, increasing intracellular calcium

C. axonal Ca+2 is increased because endoplasmic reticulum voltage-gated calcium channels open and Ca+2 enters the cytoplasm.

D. voltage-gated membrane channels open, and multiple types of ions enter the cytoplasm, increasing the intracellular positive charge

B. voltage-gated membrane channels open, and Ca+2 enters the cytoplasm, increasing intracellular calcium

Which statement best describes exocytosis?

A. Membrane organelles fuse with the membrane and release contents out of the cell.

B. Sodium from the action potential fuses with the membrane vesicle and releases the neurotransmitter in the cytoplasm, which can then diffuse out to the extracellular fluid.

C. Membrane organelles fuse with the membrane and release contents inside the cell

D .Membrane organelles fuse together and mix neurotransmitter.

A. Membrane organelles fuse with the membrane and release contents out of the cell.

What conditions will increase the diffusion of molecules, such as neurotransmitters?

A. An increase in the amount of neurotransmitter exocytized by the presynaptic axon.

B. An increase in the distance between the neurons.

C. An increase in number of postsynaptic receptors.

D. An increased viscosity of the fluid between neurons.

A. An increase in the amount of neurotransmitter exocytized by the presynaptic axon.

If the membrane of a postsynaptic dendrite is setting up a graded potential, what must have happened after neurotransmitter was released by the presynaptic terminal?
The neurotransmitter:

A. bound at postsynaptic receptors to open postsynaptic ion channels.

B. was reabsorbed by the presynaptic membrane before it diffused away.

C. was degraded by enzymes before arriving at the postsynaptic membrane.

D. bound at postsynaptic receptors to initiate an action potential.

A. bound at postsynaptic receptors to open postsynaptic ion channels.

Which best represents synaptic transmission?

A. presynaptic axon to presynaptic cell body to dendrite

B. presynaptic axon to synapse to postsynaptic axon

C. presynaptic cell body to dendrite to synapse

D. presynaptic axon to synapse to dendrite or postsynaptic cell body

D. presynaptic axon to synapse to dendrite or postsynaptic cell body

Predict the possible effect of a drug that totally blocks the neurotransmitter receptor on the postsynaptic membrane.
For example, curare is a neurotoxin used by several South American cultures. The primary effect of curare is that acetylcholine, a major neuromuscular neurotransmitter, cannot bind at its receptor because curare is blocking it. Predict the possible effects of curare on the postsynaptic membrane and muscle.

A. Transmission is slowed and there is a slower response.

B. There is no effect.

C. Local graded potentials and action potential transmission is blocked and there is no response by the postsynaptic cell, the muscle.

D. Transmission of the action potential will be enhanced and there is a faster contraction response by the muscle.

C. Local graded potentials and action potential transmission is blocked and there is no response by the postsynaptic cell, the muscle.

A postsynaptic cell can be a neuron, a muscle cell, or a secretory cell. What is an example of a presynaptic cell?

A. a muscle cell

B. a neuron

C. a secretory cell

D. a Schwann cell

B. a neuron

Which component has a role in the postsynaptic cell during synaptic activity?

A. chemically gated channels

B. Vesicles filled with neurotransmitter

C. axon terminal

D. calcium channels

A. chemically gated channels

What is the role of calcium in synaptic activity?

A. Calcium influx into the axon causes an action potential to propagate into the synaptic terminal.

B. Calcium degrades neurotransmitter in the synaptic cleft.

C. Calcium influx into the synaptic terminal causes vesicle fusion.

D. Calcium diffuses across the synaptic cleft and binds to receptors on the postsynaptic neuron.

C. Calcium influx into the synaptic terminal causes vesicle fusion.

What is the role of neurotransmitter at a chemical synapse?

A. Neurotransmitter causes vesicles to fuse with the presynaptic membrane.

B. Neurotransmitter causes a graded potential in the postsynaptic cell.

C. Neurotransmitter causes calcium to flood into the presynaptic cell.

D. Neurotransmitter binds to receptors on the postsynaptic cell membrane and allows ions to diffuse across the membrane.

D. Neurotransmitter binds to receptors on the postsynaptic cell membrane and allows ions to diffuse across the membrane.

Neurotransmitter is released from presynaptic neurons through what mechanism?

A. phagocytosis

B. exocytosis

C. endocytosis

D. pinocytosis

B. exocytosis

What type of channel on the postsynaptic membrane binds neurotransmitter?

A. a leakage channel

B. a chemically gated channel

C. a voltage-gated channel

D. a mechanically gated channel

B. a chemically gated channel

In addition to diffusion, what are two other mechanisms that terminate neurotransmitter activity?

A. excitation and degradation

B. reuptake and inhibition

C. reuptake and degradation

D. exocytosis and degradation

C. reuptake and degradation

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