A&P 1- Swiger (Chapter 11)

True or False: In myelinated axons the voltage-regulated sodium channels are concentrated at the nodes of Ranvier.

True

Which ion channel opens in response to a change in membrane potential and participates in the generation and conduction of action potentials?

mechanically gated channel
ligand-gated channel
leakage channel
voltage-gated channel

voltage-gated channel

True or False: If the neuron membrane becomes more permeable to Na+, Na+ will transport across the membrane, causing the cell to depolarize.

True

True or False: During depolarization, the inside of the neuron’s membrane becomes less negative.

True

Which of the following correctly describes a graded potential?

it can have amplitudes of various sizes
it travels long distances
it is initiated by voltage changes in the membrane
it has a depolarization, repolarization and hyperpolarization phase

it can have amplitudes of various sizes

Which of the following is not true of graded potentials?

They can be called postsynaptic potentials.
They can form on receptor endings.
They are short-lived.
They increase amplitude as they move away from the stimulus point.

They increase amplitude as they move away from the stimulus point.

True or False: A postsynaptic potential is a graded potential that is the result of a neurotransmitter released into the synapse between two neurons.

True

Which membrane potential occurs because of the influx of Na+ through chemically gated channels in the receptive region of a neuron?

excitatory postsynaptic potential
inhibitory postsynaptic potential
action potential
inhibitory action potential

excitatory postsynaptic potential

You discover that a new chemical compound interacts with K+ voltage-dependent channels. What would be the effect on a neuron if the chemical came into contact with the axonal membrane?

The neuron would be unable to repolarize.
The cell would be unable to depolarize.
The cell would be unable to generate a resting potential.
The cell would die.

The neuron would be unable to repolarize.

Which of the following is NOT a difference between graded potentials and action potentials?

– The magnitude of action potentials decrease as the impulse travels further away from the start of the impulse while graded potentials do not decrease in magnitude.
– Greater stimulus intensity results in larger graded potentials, but not larger action potentials.
– Graded potentials can result from the opening of chemically gated channels; action potentials require the opening of voltage-gated channels.
– Graded potentials occur along dendrites, whereas action potentials occur along axons.

The magnitude of action potentials decrease as the impulse travels further away from the start of the impulse while graded potentials do not decrease in magnitude.

If a neuron had a mutation that prevented the production of voltage-gated Na+ channels, what function would the neuron NOT be able to accomplish?
If a neuron had a mutation that prevented the production of voltage-gated Na+ channels, what function would the neuron NOT be able to accomplish?
graded hyperpolarization
graded depolarization
resting membrane potentials
depolarization leading to action potentials

depolarization leading to action potentials

What type of stimulus is required for an action potential to be generated?

multiple stimuli
a suprathreshold stimulus
hyperpolarization
a threshold level depolarization

a threshold level depolarization

True or False: The action potential is caused by permeability changes in the plasma membrane.

True

Absolute refractory period

The neuron cannot respond to a second stimulus, no matter how strong

Depolarization

The interior of the cell becomes less negative due to an influx of sodium ions.

Repolarization

The specific period during which potassium ions diffuse out of the neuron due to a change in membrane permeability.

Action potential

Also called a nerve impulse transmitted by axons.

Relative refractory period

An exceptionally strong stimulus can trigger a response.

An action potential is regarded as an example of a positive feedback. Which of the following examples below best illustrates the positive feedback aspect of an action potential?

-Voltage gated potassium ion channels open slowly and remain open long enough to cause hyperpolarization.
– A threshold stimulus will cause the opening of voltage gated sodium ion channels that will cause further depolarizing stimulus. This stimulus will open still more voltage gated sodium ion channels.
– The sodium potassium pump consistently moves ions as long as ATP is available, and regardless of membrane potential changes.
– Potassium permeability is about 25 times greater than sodium ions.

A threshold stimulus will cause the opening of voltage gated sodium ion channels that will cause further depolarizing stimulus. This stimulus will open still more voltage gated sodium ion channels.

True or False: The all-or-none phenomenon as applied to nerve conduction states that the whole nerve cell must be stimulated for conduction to take place.

False

Which of the following correctly states the direction followed by the specified ions when their voltage-gated channels open?

.
Na+ ions move into the axon; K+ ions move out.
Both Na+ and K+ ions move out.
Both Na+ and K+ ions move in.
Na+ ions move out of the axon; K+ ions move in.

Na+ ions move into the axon; K+ ions move out.

What change in a neuron is being measured in the graph?

the voltage measured between the neuron cell body and the axonal terminals
the voltage measured across the axon membrane at a specific point as an action potential travels past
the voltage measured across the axon membrane at various points along an axon at a specific instance during an action potential
the speed of an action potential as it moves down the length of an axon

the voltage measured across the axon membrane at a specific point as an action potential travels past

Immediately after an action potential has peaked, which of the following channels will open?

voltage gated sodium channels
voltage gated potassium channels
chemically gated chloride channels
voltage gated calcium channels

voltage gated potassium channels

What does the central nervous system use to determine the strength of a stimulus?

type of stimulus receptor
size of action potentials
frequency of action potentials
origin of the stimulus

frequency of action potentials

True or False: Strong stimuli cause the amplitude of action potentials generated to increase.

False

The period after an initial stimulus when a neuron is not sensitive to another stimulus is the ________.

absolute refractory period
depolarization
repolarization
resting period

absolute refractory period

Which of the following is a factor that determines the rate of impulse propagation, or conduction velocity, along an axon?

whether the axon is located in the central nervous system or in the peripheral nervous system
degree of myelination of the axon
the number of axon collaterals extending from a truncated axon
length of the axon

degree of myelination of the axon

Saltatory conduction is made possible by ________.

the myelin sheath
diphasic impulses
erratic transmission of nerve impulses
large nerve fibers

the myelin sheath

How is an action potential propagated along an axon?

An influx of sodium ions from the current action potential depolarizes the adjacent area.
An efflux of potassium from the current action potential depolarizes the adjacent area.
Stimuli from the graded (local) potentials from the soma and dendrites depolarize the entire axon.

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?

The flow of the sodium ions only goes in one direction—away from the cell body
The areas that have had the action potential are refractory to a new action potential.

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 small myelinated axon
a large unmyelinated axon
a small unmyelinated axon

a small myelinated axon

Where do most action potentials originate?

Initial segment
Cell body
Nodes of Ranvier
Axon terminal

Initial segment

What opens first in response to a threshold stimulus?

Voltage-gated Na+ channels
Ligand-gated cation channels
Ligand-gated Cl- channels
Voltage-gated K+ channels

Voltage-gated Na+ channels

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

The membrane potential changes to a much more negative value.
The membrane potential reaches a threshold value and returns to the resting state.
The membrane potential changes from a negative value to a positive value.
The membrane potential changes to a less negative (but not a positive) value.

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

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

Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.
Before the membrane has a chance to reach a positive voltage, it repolarizes to its negative resting value of approximately -70 mV.
As the membrane repolarizes to a negative value, it goes beyond the resting state to a value of -80 mV.
Once the membrane depolarizes to a threshold value of approximately -55 mV, it repolarizes to its resting value of -70 mV.

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?
What event triggers the generation of an action potential?
The membrane potential must depolarize from the resting voltage of -70 mV to its peak value of +30 mV.
The membrane potential must hyperpolarize from the resting voltage of -70 mV to the more negative value of -80 mV.
The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.
The membrane potential must return to its resting value of -70 mV from the hyperpolarized value of -80 mV.

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?
What is the first change to occur in response to a threshold stimulus?
Voltage-gated K+ channels change shape, and their activation gates open.
Voltage-gated Ca2+ channels change shape, and their activation gates open.
Voltage-gated Na+ channels change shape, and their inactivation gates close.
Voltage-gated Na+ channels change shape, and their activation gates open.

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

What type of conduction takes place in unmyelinated axons?

Continuous conduction
Saltatory conduction
Synaptic transmission
Electrical conduction

Continuous conduction

An action potential is self-regenerating because __________.

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

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?

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

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?

The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
The myelin sheath decreases the resistance of the axonal membrane to the flow of charge.
The myelin sheath increases the insulation along the entire length of the axon.
The myelin sheath decreases the speed of action potential conduction from the initial segment to the axon terminals.

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?

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

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?

Myelinated axons with the smallest diameters
Unmyelinated axons with the largest diameter
Myelinated axons with the largest diameter
Unmyelinated axons of the shortest length

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?

Na+ is entering the cell.
K+ is exiting the cell.
Na+ is exiting the cell.
K+ is entering the cell.

Na+ is entering the cell.

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

at the end of the repolarization phase, as the membrane potential briefly passes its resting value
at the end of the depolarization phase, as the membrane potential approaches its peak value
at the end of the hyperpolarization phase of an action potential, as the membrane potential returns to its resting value
at the beginning of an action potential, as the membrane potential reaches threshold

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 __________.

K+ ions entering the cell through voltage-gated channels
K+ ions leaving the cell through voltage-gated channels
Na+ ions transported out of the cell by the Na+-K+ pump
Na+ ions leaving the cell through voltage-gated channels

K+ ions entering the cell through voltage-gated channels

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

Na+ diffusing through voltage-gated channels
K+ ions diffusing through voltage-gated channels
K+ ions diffusing through leakage channels
Na+-K+ pump activity

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?

K+ channels close. Na+ channels open.
K+ channels open. Na+ channels inactivate.
K+ channels close. Na+ channels go from an inactivated state to a closed state.
K+ channels close. Leakage channels open.

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?

The membrane would depolarize and repolarize as usual, but no hyperpolarization beyond (more negative to) the resting membrane potential would occur.
The action potential would fail. Once the voltage reached threshold, it would return to the resting membrane potential.
The membrane would depolarize as usual but then stay at that depolarized voltage (about +30 mV).
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 action potential would depolarize as usual, but the repolarization phase would take longer, causing the action potential to be more broad in time.

Which description best fits graded potentials?

Graded potentials are all-or-nothing events.
Graded potentials can result in either depolarization or hyperpolarization of the membrane and vary in strength.
Graded potentials are found only along the axon of a neuron.
Graded potentials are caused only by the influx of sodium ions.

Graded potentials can result in either depolarization or hyperpolarization of the membrane and vary in strength.

What is meant by an EPSP?

a localized change in the membrane potential that makes a neuron less likely to send a signal
a localized change in the membrane potential that always results in threshold being reached
a localized change in the membrane potential resulting in a more negative membrane voltage
a localized change in the membrane potential resulting in a less negative membrane voltage

a localized change in the membrane potential resulting in a less negative membrane voltage

What kinds of gated channels are typically found in high concentrations at the dendrites?

both voltage-gated and chemically gated
neither voltage-gated nor chemically gated
voltage-gated
chemically gated

chemically gated

What must occur for threshold to be reached?

Enough excitatory potentials add up to open chemically gated channels at the axon hillock.
Enough excitatory potentials add up to open voltage-gated channels at the axon hillock.
Enough inhibitory potentials add up to open voltage-gated channels at the axon hillock.
Enough inhibitory potentials prevent the opening of voltage-gated channels at the axon hillock.

Enough excitatory potentials add up to open voltage-gated channels at the axon hillock.

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?

Na+ is exiting the cell.
K+ is entering the cell.
Na+ is entering the cell.
K+ is exiting the cell.

Na+ is entering the cell.

What is happening to voltage-gated channels at this point in the action potential?

(The figure shows the phases of action potential. The arrow points to the peak potential.)

Na+ channels are inactivating, and K+ channels are opening.
Both Na+ and K+ channels are opening.
Na+ channels are inactivating, and K+ channels are closing.
Na+ channels are opening, and K+ channels are closing.

Na+ channels are inactivating, and K+ channels are opening.

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

at the beginning of an action potential, as the membrane potential reaches threshold
at the end of the repolarization phase, as the membrane potential briefly passes its resting value
at the end of the hyperpolarization phase of an action potential, as the membrane potential returns to its resting value
at the end of the depolarization phase, as the membrane potential approaches its peak value

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 __________.

Na+ ions leaving the cell through voltage-gated channels
Na+ ions transported out of the cell by the Na+-K+ pump
K+ ions leaving the cell through voltage-gated channels
K+ ions entering the cell through voltage-gated channels

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 __________.

Na+ diffusing through voltage-gated channels
K+ ions diffusing through voltage-gated channels
K+ ions diffusing through leakage channels
Na+-K+ pump activity

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?

K+ channels open. Na+ channels inactivate.
K+ channels close. Leakage channels open.
K+ channels close. Na+ channels open.
K+ channels close. Na+ channels go from an inactivated state to a closed state.

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?

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 membrane would depolarize and repolarize as usual, but no hyperpolarization beyond (more negative to) the resting membrane potential would occur.
The membrane would depolarize as usual but then stay at that depolarized voltage (about +30 mV).
The action potential would fail. Once the voltage reached threshold, it would return to the resting membrane potential.

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

True or False: The all-or-none phenomenon as applied to nerve conduction states that the whole nerve cell must be stimulated for conduction to take place.

False

The period after an initial stimulus when a neuron is not sensitive to another stimulus is the ________.

depolarization
resting period
absolute refractory period
repolarization

absolute refractory period

Saltatory conduction is made possible by ________.

erratic transmission of nerve impulses
the myelin sheath
diphasic impulses
large nerve fibers

the myelin sheath

In multiple sclerosis, the cells that are the target of an autoimmune attack are the _________.

neurons
muscle cells
Schwann cells
oligodendrocytes

oligodendrocytes

Select the correct statement regarding chemical synapses.

Neurotransmitter receptors are located on the axons terminals of cells.
Cells with gap junctions use chemical synapses.
The synaptic cleft transmits a chemical signal to the post synaptic cell through diffusion of neurotransmitters across the cleft.
The release of neurotransmitter molecules gives cells the property of being electrically coupled.

The synaptic cleft transmits a chemical signal to the post synaptic cell through diffusion of neurotransmitters across the cleft.

What ion is entering the axon terminal at A, and what effect does it have?

(Steps in communication between pre and postsynaptic neurons at a chemical synapse.)

K+, which then causes increased production of neurotransmitter
Na+, which then causes repolarization of the axon terminal’s membrane
Ca2+, which then causes release of neurotransmitter from the axon terminal
neurotransmitter, which then causes the presynaptic neuron to form an action potential

Ca2+, which then causes release of neurotransmitter from the axon terminal

By which method does the structure at B release neurotransmitter?

(Steps in communication between pre and postsynaptic neurons at a chemical synapse.)

exocytosis
passive diffusion
facilitated diffusion
active transport

exocytosis

How would the receptors at C best be classified?

(Steps in communication between pre and postsynaptic neurons at a chemical synapse.)

mechanically gated
voltage gated
chemically gated

chemically gated

The box labeled D illustrates three mechanisms by which the effects of a neurotransmitter may be terminated. Which of the following mechanisms is NOT included in the figure?

(Steps in communication between pre and postsynaptic neurons at a chemical synapse.)

reuptake of the neurotransmitter by transport into the postsynaptic cell
reuptake of the neurotransmitter by transport into the presynaptic cell
diffusion of the neurotransmitter out of the synaptic cleft
breakdown of the neurotransmitter within the synaptic cleft

reuptake of the neurotransmitter by transport into the postsynaptic cell

In a lab you are conducting tests with various chemicals and neurotransmitter receptors. You notice that exposed frog muscle cells depolarize when you add the chemical nicotine to the acetylcholine (ACh) receptors. What does this tell us about the relationship between neurotransmitters and their receptors?

The response generated by a receptor is very broad in nature.
The effect of a neurotransmitter is based on the properties of the neurotransmitter more than the receptor.
Neurotransmitter receptors only bind specifically with their neurotransmitter.
The effect of a neurotransmitter is based on the properties of the receptor more than the neurotransmitter.

The effect of a neurotransmitter is based on the properties of the receptor more than the neurotransmitter.

Suppose that both stimuli seen in these graphs happened equally at the same time on a postsynaptic membrane as a result of two different synapses. Which of the following best describes the result?

(Examples of postsynaptic potentials resulting from different stimuli.)

There would be little or no graded potential.
Temporal summation would occur.
An action potential would result.
No chemically gated ion channels would open.

There would be little or no graded potential.

Which of the following statements is true of both membrane potential responses shown in the graphs?

(Examples of postsynaptic potentials resulting from different stimuli.)

Both responses are examples of action potentials.
Both responses are examples of inhibitory postsynaptic potentials (IPSPs).
Both responses are examples of graded potentials.
Both responses are examples of excitatory postsynaptic potentials (EPSPs).

Both responses are examples of graded potentials.

Which of the following stimuli caused the reaction in the graph on the left?

Examples of postsynaptic potentials resulting from different stimuli.

opening of gated K+ channels
opening of gated Ca2+ channels
opening of gated Na+ channels
opening of gated Cl- channels

opening of gated Na+ channels

Which of the following is expected to occur first if the membrane potential decrease shown in the graph on the left were to reach the threshold value indicated at −55 mV?

(Examples of postsynaptic potentials resulting from different stimuli.)

opening of voltage-gated Na+ channels
opening of chemically gated Na+ channels
opening of voltage-gated K+ channels
opening of chemically gated K+ channels

opening of voltage-gated Na+ channels

True or False: Opening K+ or Cl- channels in a postsynaptic membrane would produce an inhibitory postsynaptic potential (IPSP).

True

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

postsynaptic neuron
presynaptic neuron
synaptic cleft

presynaptic neuron

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

voltage-gated Na+ channels
voltage-gated Ca2+ channels
chemically gated Ca2+ channels
voltage-gated K+ channels

voltage-gated Ca2+ channels

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

chemically gated; postsynaptic
chemically gated; presynaptic
voltage-gated; presynaptic
voltage-gated; postsynaptic

chemically gated; postsynaptic

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

either depolarize or hyperpolarize
hyperpolarize
depolarize

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?

glutamate
acetylcholine

acetylcholine

Which of the following is false or incorrect?

A nerve impulse occurs if the excitatory and inhibitory effects are equal.
An excitatory postsynaptic potential occurs if the excitatory effect is greater than the inhibitory effect but less than threshold.
An inhibitory postsynaptic potential occurs if the inhibitory effect is greater than the excitatory, causing hyperpolarization of the membrane.

A nerve impulse occurs if the excitatory and inhibitory effects are equal.

An inhibitory postsynaptic potential (IPSP) is associated with ________.

hyperpolarization
lowering the threshold for an action potential to occur
opening of voltage-regulated channels
a change in sodium ion permeability

hyperpolarization

Which of the following will occur when an excitatory postsynaptic potential (EPSP) is being generated on the dendritic membrane?

Specific sodium gates will open.
A single type of channel will open, permitting simultaneous flow of sodium and potassium.
Sodium gates will open first, then close as potassium gates open.
Specific potassium gates will open.

A single type of channel will open, permitting simultaneous flow of sodium and potassium.

Which of the following describes the excitatory postsynaptic potential?

opens K+ or Cl- channels
short distance hyperpolarization
short distance depolarization
moves membrane potential away from threshold

short distance depolarization

Temporal summation

Numerous nerve impulses arriving at a synapse at closely timed intervals exert a cumulative effect.

Spatial summation

Stimulation of a postsynaptic neuron by many terminals at the same time.

Subthreshold stimulus:

An insufficient stimulus to reach an action potential.

Threshold stimulus:

Any stimulus at or above this level will result in action potential.

If a post synaptic neuron is stimulated to threshold by spatial summation this implies that ________.

the post synaptic cell is slow to repolarize
the post synaptic cell has many voltage gated ion channels
the postsynaptic cells has many synapses with many presynaptic neurons
the post synaptic cell has a lower than normal threshold

the postsynaptic cells has many synapses with many presynaptic neurons

Loss of function in the enzyme acetylcholinesterase would result in which of the following?

inability to release acetylcholine
decrease or reduce the effect of ACh
stimulation of the production of acetylcholine
inability to destroy and remove acetylcholine from the synaptic cleft

inability to destroy and remove acetylcholine from the synaptic cleft

The effect of acetylcholine can be stimulating or inhibiting. Which of the following gives the best explanation for why this is so?

Postsynaptic cells have a dynamic and changing metabolism and respond differently at different times.
Different post synaptic cells will have different receptors.
Acetylcholine has a "dose effect". Larger doses are stimulating while small doses inhibit.
Acetylcholine has many different forms.

Different post synaptic cells will have different receptors.

Which of the following is not a chemical class of neurotransmitters?

biogenic amine
nucleic acid
ATP and other purines
amino acid

nucleic acid

When a neurotransmitter like acetylcholine is acting in an excitatory manner which of the following is likely a result of the acetylcholine acting on the post synaptic cell?

Chemically gated sodium channels will open.
Chemically gated sodium channels will be closed.
Chemically gated potassium channels will open.
Chemically gated chloride channels will open.

Chemically gated sodium channels will open.

When a neurotransmitter like GABA is acting in an inhibitory manner which of the following is likely a result of the GABA acting on the post synaptic cell?

opening of chemically gated sodium channels
hyperpolarization of the postsynaptic cell membrane
influx of positively charged ions into the postsynaptic cell
depolarization of the postsynaptic cell membrane

hyperpolarization of the postsynaptic cell membrane

Which of the following is an excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle?

norepinephrine
acetylcholine
cholinesterase
gamma aminobutyric acid

acetylcholine

Which of the following neurotransmitters inhibits pain and is mimicked by morphine, heroin, and methadone?

acetylcholine
endorphin
serotonin
nitric oxide

endorphin

True or False: Enkephalins and endorphins are peptides that act like morphine.

True

What component of the reflex arc determines the response to a stimulus?

integration center
sensory neuron
effector
receptor

integration center

Which of the following circuit types is involved in the control of rhythmic activities such as the sleep-wake cycle, breathing, and certain motor activities (such as arm swinging when walking)?

parallel after-discharge circuits
reverberating circuits
diverging circuits
converging circuits

reverberating circuits

In the brain, vision originates in the rods and cones in the retina. Separate regions of the brain decode basic information, like color, shapes, intensity of light, and there are other regions that decode information like position in space, and awareness of patterns. As you use your visual system, all of these regions are working simultaneously. This simultaneous awareness of all regions working at the same time is due to which processing pattern listed below?

parallel processing
oscillative processing
reflexive processing
serial processing

parallel processing

Which of the following is NOT a type of circuit?

reverberating circuits
diverging circuits
pre-synaptic circuits
converging circuits

pre-synaptic circuits

Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing?

reverberating circuit
diverging circuit
parallel after-discharge circuit
converging circuit

reverberating circuit

A synaptic cleft, or synaptic gap, can be found between a neuron and ______.

another neuron.
All of these.
a muscle cell.
a gland.

All of these.

The membrane potential that occurs when neurotransmitters bind to their receptors is called _______.

a postsynaptic potential
an action potential and a receptor
a receptor potential
an action potential

a postsynaptic potential

The release of neurotransmitter occurs _______.

all along the axon
at the axon terminal
from the motor endplate

at the axon terminal

Which of the following occurs first?

Voltage-gated calcium channels are opened.
Synaptic vesicles exit by exocytosis.
An action potential arrives at the axon terminal.
Extracellular calcium enters the axon terminal.

An action potential arrives at the axon terminal.

Are biogenic amine neurotransmitters such as dopamine considered to be proteins?

No, it simply means that dopamine has at least one amine functional group in its molecular structure.
Yes, dopamine is a protein because of its expression of a nitrogen-containing amine group.
Yes, amines are naturally occurring organic compounds composed of amino acids.
No, dopamine cannot be a protein since proteins do not exhibit neurotransmitter activity.

No, it simply means that dopamine has at least one amine functional group in its molecular structure.

Prozac belongs to a class of drugs known as selective serotonin reuptake inhibitors (SSRIs), which block the removal of serotonin from its receptor, thereby enhancing a patient’s mood. What mechanism allows serotonin to remain on its receptors longer?

-SSRIs prevent the release of serotonin by making a permanent neurotransmitter-receptor complex on the postsynaptic membrane.
– SSRIs are not as easily degraded by acetylcholinesterase, which allows them to remain on their receptors for an extended period of time.
– SSRIs cause an increased number of serotonin receptors expressed on the presynaptic neuron membrane.
-SSRIs inhibit the reuptake of serotonin back into the presynaptic neuron, which increases the level of serotonin in the synaptic cleft.

SSRIs inhibit the reuptake of serotonin back into the presynaptic neuron, which increases the level of serotonin in the synaptic cleft.

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

a neuron
a muscle cell
a Schwann cell
a secretory cell

a neuron

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

chemically gated channels
calcium channels
Vesicles filled with neurotransmitter
axon terminal

chemically gated channels

What is the role of calcium in synaptic activity?

– Calcium influx into the synaptic terminal causes vesicle fusion.
– Calcium degrades neurotransmitter in the synaptic cleft.
-Calcium influx into the axon causes an action potential to propagate into the synaptic terminal.
-Calcium diffuses across the synaptic cleft and binds to receptors on the postsynaptic neuron.

Calcium influx into the synaptic terminal causes vesicle fusion.

What is the direct role of neurotransmitter at a chemical synapse?

-Neurotransmitter binds to receptors on the postsynaptic cell membrane and allows ions to diffuse across the membrane.
-Neurotransmitter causes a graded potential in the postsynaptic cell. -Neurotransmitter causes calcium to flood into the presynaptic cell.
-Neurotransmitter causes vesicles to fuse with the presynaptic membrane.

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?

pinocytosis
endocytosis
exocytosis
phagocytosis

exocytosis

What type of channel on the postsynaptic membrane binds neurotransmitter?

a leakage channel
a mechanically gated channel
a chemically gated channel
a voltage-gated channel

a chemically gated channel

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

reuptake and degradation
excitation and degradation
exocytosis and degradation
reuptake and inhibition

reuptake and degradation

Events that occur during synaptic activity are listed here, but they are arranged in an incorrect order. Choose the correct order of these events below. (a) Voltage-gated calcium channels open (b) Neurotransmitter binds to receptors (c) Action potential arrives at axon terminal (d) Neurotransmitter is removed from the synaptic cleft (e) Neurotransmitter released into synaptic cleft (f) Graded potential generated in postsynaptic cell

(c) Action potential arrives at axon terminal (a) Voltage-gated calcium channels open (e) Neurotransmitter released into the synaptic cleft (d) Neurotransmitter is removed from the synaptic cleft (b) Neurotransmitter binds to receptors (f) Graded potential generated in postsynaptic cell
(c) Action potential arrives at axon terminal (a) Voltage-gated calcium channels open (e) Neurotransmitter released into synaptic cleft (b) Neurotransmitter binds to receptors (f) Graded potential generated in postsynaptic cell (d) Neurotransmitter is removed from the synaptic cleft
(a) Voltage-gated calcium channels open (e) Neurotransmitter released into the synaptic cleft (c) Action potential arrives at axon terminal (b) Neurotransmitter binds to receptors (f) Graded potential generated in postsynaptic cell (d) Neurotransmitter is removed from the synaptic cleft
(d) Neurotransmitter is removed from the synaptic cleft (b) Neurotransmitter binds to receptors (f) Graded potential generated in postsynaptic cell (c) Action potential arrives at axon terminal (a) Voltage-gated calcium channels open (e) Neurotransmitter released into the synaptic cleft

(c) Action potential arrives at axon terminal (a) Voltage-gated calcium channels open (e) Neurotransmitter released into synaptic cleft (b) Neurotransmitter binds to receptors (f) Graded potential generated in postsynaptic cell (d) Neurotransmitter is removed from the synaptic cleft

Which of the following is NOT one of the basic functions of the nervous system?

Generate direct, electrical signals.
Decode sensory information from the environment.
Integrate sensory input for decision making.
Release hormones into the bloodstream to communicate with other cells in the body.

Release hormones into the bloodstream to communicate with other cells in the body.

The term central nervous system refers to the ________.

the somatic nerves
brain and spinal cord
sensory (afferent) nerves
the spinal nerves

brain and spinal cord

Collections of nerve cell bodies in the peripheral nervous system are called ________.

ganglia
tracts
nuclei
nerves

ganglia

True or False: Cell bodies of sensory neurons may be located in ganglia lying outside the central nervous system

True

As you start working out, you notice that your heart rate and breathing rate start to increase. Which division of your nervous system is generating this response? Be as specific as possible.

the sympathetic division of the autonomic nervous system
the parasympathetic division of the autonomic nervous system
the afferent division of the nervous system
the somatic nervous system

the sympathetic division of the autonomic nervous system

What division of the nervous system is most specifically responsible for voluntary motor control?

somatic nervous system
central nervous system
parasympathetic nervous system
sympathetic nervous system

somatic nervous system

Nerve impulses leading to the skeletal muscle carry information to direct movement. The nerve fibers sending these signals will most likely belong to which division of the nervous system?

sensory (afferent) division
somatic nervous system
sympathetic division
parasympathetic division

somatic nervous system

Which of the following is not a function of the autonomic nervous system?

innervation of skeletal muscle
innervation of glands
innervation of smooth muscle of the digestive tract
innervation of cardiac muscle

innervation of skeletal muscle

Which of the choices below describes the ANS?

motor fibers that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands
sensory and motor neurons that supply the digestive tract
motor fibers that conduct nerve impulses from the CNS to skeletal muscles
sensory neurons that convey information from somatic receptors in the head, body wall, and limbs and from receptors from the special senses of vision, hearing, taste, and smell to the CNS

motor fibers that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands

True or False: Neurons in the CNS are organized into functional groups.

True

Which glial cells have the most diversity of function?

oligodendrocytes
Schwann cells
astrocytes
ependymal cells

astrocytes

The concentration of ions in the chemical environment surrounding the neurons must be tightly regulated for neurons to function properly. Which of the following cells is most responsible for this?

satellite cells
astrocytes
Schwann cells
oligodendrocytes

astrocytes

The concentration neurotransmitters in the fluid of the synaptic cleft must be tightly regulated for neurons to function properly. Which of the following cells is most responsible for aiding in this regulation?

satellite cells
astrocytes
Schwann cells
oligodendrocytes

astrocytes

Bacteria in the blood can be prevented entry to the fluids surrounding the brain. Which cells are most responsible for preventing bacteria from entering the fluids of the brain?

satellite cells
astrocytes
Schwann cells
oligodendrocytes

astrocytes

Which of the following is not a function of astrocytes?

anchor neurons to blood vessels
provide the defense for the CNS
support and brace neurons
guide the migration of young neurons, synapse formation, and helping to determine capillary permeability
control the chemical environment around neurons

provide the defense for the CNS

Which of the following types of glial cells monitors the health of neurons, and can transform into a special type of macrophage to protect endangered neurons?

ependymal cells
astrocytes
oligodendrocytes
microglia

microglia

Meningitis can be caused by infection of the central nervous system by bacteria. Which cells would be most responsible for removing the infection?

oligodendrocytes
microglia
satellite cells
Schwann cells

microglia

These cells in the CNS have cilia that move in order to circulate cerebrospinal fluid ________.

astrocytes
ependymal cells
oligodendrocytes
Schwann cells

ependymal cells

Which of the following peripheral nervous system (PNS) neuroglia form the myelin sheaths around larger nerve fibers in the PNS?

astrocytes
satellite cells
Schwann cells
oligodendrocytes

Schwann cells

Ependymal cells line many open cavities in the central nervous system (CNS). Ependymal cells have cilia on the side of the cell that face these openings. What is the most likely function of these ciliated cells?

create myelin sheaths for CNS cells
act as macrophage cells to destroy microorganisms or neuronal debris
movement and circulation of cerebrospinal fluid
exchange of nutrients between the circulatory system and neurons

movement and circulation of cerebrospinal fluid

Which of the following is not characteristic of neurons?

They have extreme longevity.
They conduct impulses.
They have an exceptionally high metabolic rate.
They are mitotic.

They are mitotic.

Schwann cells are functionally similar to ________.

microglia
ependymal cells
astrocytes
oligodendrocytes

oligodendrocytes

How do neurofibrils differ from nerve fibers?

Neurofibrils are cytoskeletal intermediate filaments maintaining cell shape, but they do not conduct impulses.
There is no real difference, since they are both capable of impulse conduction away from a neuron.
Neurofibrils are confined to dendrite receptor areas and are consequently not found in nerve fibers.
Neurofibrils are axon subunits that are bundled together to make up a single nerve fiber

Neurofibrils are cytoskeletal intermediate filaments maintaining cell shape, but they do not conduct impulses.

Which is the main receptive portion of the neuron?

the axon
the synapse
the cell body or soma
the dendrite

the dendrite

Many neurons have many short, branching extensions called dendrites. What is the benefit of these structures for a neuron?

There is a large amount of space for myelin to form and make electrical conduction more efficient.
There is a large area for production of chemicals used to signal other neurons.
The dendrites provide a large surface area for connections from other neurons.
There is a large surface area to send signals to other cells.

The dendrites provide a large surface area for connections from other neurons.

True or False: Bundles of neurons in the central nervous system are called tracts.

True

Which of the following is true of axons?

Neurons can have multiple axons but only one dendrite.
Smaller (thinner) axons are more likely to bear myelin sheaths than larger (thicker) axons.
Axons use chemically gated ion channels to generate graded potentials.
A neuron can have only one axon, but the axon may have occasional branches along its length.

A neuron can have only one axon, but the axon may have occasional branches along its length.

Cold sores on the skin of the mouth occur when herpes simplex viruses that are dormant in neural ganglia become active and travel to the skin of the mouth. Which of the following is the mechanism by which these viruses travel from the ganglia (located within the head) to the skin of the mouth?

transport along nerve impulses that travel down the axons
anterograde axonal transport
retrograde axonal transport
travel of the viruses along neurofibrils

anterograde axonal transport

Which criterion is used to functionally classify neurons?

the number of processes extending from the cell body neuron
the direction in which the nerve impulse travels relative to the central nervous system
whether the nerve fibers are myelinated or unmyelinated
whether the neurons are found within the CNS or the PNS

the direction in which the nerve impulse travels relative to the central nervous system

True or False: Axon diameter and degree of myelination determine nerve impulse conduction velocity.

True

Which criterion is used to functionally classify neurons?

the direction in which the nerve impulse travels relative to the central nervous system
whether the neurons are found within the CNS or the PNS
the number of processes extending from the cell body neuron
whether the nerve fibers are myelinated or unmyelinated

the direction in which the nerve impulse travels relative to the central nervous system

Which of the following pairings does NOT fit?

motor neurons: efferent neurons.
association neuron: functional classification
multipolar neurons: peripheral nervous system sensory neurons
afferent neurons: sensory neurons

multipolar neurons: peripheral nervous system sensory neurons

Like all cells, the neurons’ internal organization dictates its function. Neurons have relatively many mitochondria, an extensive network of rough endoplasmic reticulum and many clusters of ribosomes. These cellular features indicate all of the following EXCEPT ________.

neurons produce many proteins
neurons have stable, relatively unchanging internal environments
neurons must meet a high demand for ATP
neurons have a relatively high consumption of oxygen

neurons have stable, relatively unchanging internal environments

Bipolar neurons are commonly ________.

found in ganglia
found in the retina of the eye
called neuroglial cells
motor neurons

found in the retina of the eye

True or False: Unipolar neurons have axons structurally divided into peripheral and central processes.

True

Which of the following statements is correct regarding the polarization of a neuronal membrane and the formation of a resting membrane potential?

Sodium/Potassium pumps maintain concentration gradients; sodium and potassium move down their concentration gradients through leakage channels.
A resting potential can be generated without the energy as an input.
As Na+ leaks across the membrane, that establishes a negative charge inside the membrane.
As sodium leaks into the cell, the inside of the cell becomes more negative.

Sodium/Potassium pumps maintain concentration gradients; sodium and potassium move down their concentration gradients through leakage channels.

True or False: Na+ leaks through neuron membranes faster than K+ because of the properties of the non-gated leak channels.

False

The interior surface of a neuron’s plasma membrane at resting membrane potential will have a ________.

negative charge and contains less sodium than outside of the cell
positive charge and contains more sodium than outside of the cell
positive charge and contains less sodium than outside of the cell
negative charge and contains more sodium than outside of the cell

negative charge and contains less sodium than outside of the cell

Which of the following correctly describes a graded potential?

it can have amplitudes of various sizes
it travels long distances
it is initiated by voltage changes in the membrane
it has a depolarization, repolarization and hyperpolarization phase

it can have amplitudes of various sizes

Which of the following is not true of graded potentials?

They can form on receptor endings.
They are short-lived.
They increase amplitude as they move away from the stimulus point.
They can be called postsynaptic potentials.

They increase amplitude as they move away from the stimulus point.

What effect did increasing the extracellular potassium have on the resting membrane potential?

The resting membrane potential became more negative.
The resting membrane potential did not change.
The resting membrane potential became less negative.
The resting membrane potential disappeared.

The resting membrane potential became less negative.

What effect did decreasing the extracellular sodium have on the resting membrane potential?

The resting membrane potential became less negative.
Only a small change occurred, because the sodium channels were mostly open.
Only a small change occurred, because the resting neuron is not very permeable to sodium.
The resting membrane potential disappeared.

Only a small change occurred, because the resting neuron is not very permeable to sodium.

The channels that provide for the movement of potassium in the resting neuron are _______.

chemically gated
voltage gated
leakage and chemically gated.
leakage

leakage

Establishing the resting membrane potential requires energy through the use of the _______.

sodium-glucose pump
potassium-glucose pump
sodium-potassium pump
sodium leakage channels

sodium-potassium pump

Which of the following statements about receptor potentials is FALSE?

They can trigger an action potential.
The receptor potential is carried by neuroglia.
Odor molecules can act as stimuli.
The receptor proteins respond to stimuli.

The receptor potential is carried by neuroglia.

Which of the following is NOT a functional region of a neuron?

medullary region
conducting region
secretory region
receiving region

medullary region

The conducting region of the neuron is the _______.

axon terminal
axon
dendrite
cell body

axon

The typical concentration of sodium is _______.

higher than potassium intracellularly.
the same as potassium intracellularly.
lower than potassium extracellularly.
lower than potassium intracellularly

lower than potassium intracellularly

Which of the following describes a change from the resting membrane potential?

a receptor potential, a synaptic potential or an action potential
an action potential
a receptor potential
a synaptic potential

a receptor potential, a synaptic potential or an action potential

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

K+; Cl-
Na+; Cl-
Na+; K+
K+; Na+

K+; Na+

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

only the chemical gradient
both the electrical and chemical gradients
Na+ does not move into the cell. Na+ moves out of the cell.
only the electrical gradient

both the electrical and chemical gradients

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

+30 mV
-90 mV
-70 mV

-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?

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

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.

Na+ and A- (negatively charged proteins)
Na+ and Cl-
K+ and Cl-
K+ and A- (negatively charged proteins)

Na+ and Cl-

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?

Resting membrane potential (RMP)
Action potential
Positive membrane potential
Threshold potential

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?

Leak channels
Voltage-gated channels
Sodium-potassium ATPases
Ligand-gated channels

leak channels

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

Ligand-gated cation channels favor a greater influx of Na+ than K+.
There are many more K+ leak channels than Na+ leak channels in the plasma membrane.
There are many more voltage-gated K+ channels than voltage-gated Na+ channels.
The Na+-K+ pumps transport more K+ into cells than Na+ out of cells.

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.

The presence of concentration gradients and voltage-gated channels
The presence of concentration gradients and Na+-K+ pumps
The presence of concentration gradients and leak channels
The presence of a resting membrane potential and leak channels

The presence of concentration gradients and leak channels

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

Na+ cotransporter
Na+ and K+ leaks
Na+-K+ ATPase
H+-K+ ATPase

Na+-K+ ATPase

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

The Na+ concentration is higher outside the cell compared to inside. The K+ concentration is higher inside the cell compared to outside.
Both Na+ and K+ concentrations are higher inside the cell compared to outside.
The Na+ concentration is higher inside the cell compared to outside. The K+ concentration is higher outside the cell compared to inside.
Both Na+ and K+ concentrations are higher outside the cell compared to inside.

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?

permitting Na+ and K+ ions to diffuse across the plasma membrane
hydrolyzing ATP
making the membrane potential negative by moving more Na+ ions out of the cell than K+ ions into the cell
maintaining the concentration gradients for Na+ and K+ across the cell membrane

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?

The Na+-K+ pump only transports Na+ and K+ ions.
The concentration gradient for Na+ ions is inward, but the concentration gradient for K+ ions is outward.
K+ ions can diffuse across the membrane more easily than Na+ ions.
Diffusion of K+ ions out of the neuron causes the membrane potential to become more negative.

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

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

more Na+ leakage channels
a greater concentration gradient for K+
more K+ leakage channels
more negative membrane potential

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?

The resting membrane potential would become more negative.
The concentration gradient for Na+ would decrease.
The concentration gradient for K+ would decrease.
The resting membrane potential would become less negative (more positive).

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?

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

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

What is the electrochemical gradient of an ion?

the difference between the inside and outside concentrations of that ion
the direction an ion would tend to diffuse based on the membrane potential
the membrane potential at which the electrical gradient and concentration gradient for that ion are equal in magnitude, but opposite in direction
the sum of the electrical and concentration gradients for that ion

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?

The inward concentration gradient for Na+ would become larger.
The outward concentration gradient for K+ would become smaller.
The resting membrane potential would become more negative.
The resting membrane potential would become less negative (more positive).

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

The concentration of _____ is higher inside than outside the cell.

K+

The concentration of ______ is higher outside than inside the cell.

Na+

The resting membrane potential is maintained by Na+-K+ pumps that actively transport _____ into and ______ out of the cell.

K+ ; Na+

The membrane is more permeable to ______.

K+.

Which choice best characterizes K+ leak channels?

transmembrane protein channels that are always open to allow K+ to cross the membrane without the additional input of energy
common transmembrane channels that are always open for any ion to move through in the presence of K+
transmembrane channels that use energy to allow the movement of K+ across the membrane
chemically gated K+ channels that open and close according to the binding of other molecules

transmembrane protein channels that are always open to allow K+ to cross the membrane without the additional input of energy

Sodium (Na+) Leak Channels, Part I

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 __________.

+90 mV
-70 mV
+70 mV
-90 mV
-50 mV

-70 mV

Sodium (Na+) Leak Channels, Part II

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

The RMP will be zero.
The RMP will be more positive.
The RMP will be more negative.
The RMP will be unaffected.

The RMP will be more positive.

Leak Channels and Na+-K+ Pumps

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

moves 2 Na+ to the ECF and 3 K+ to the cytoplasm
moves 3 Na+ to the ECF and 2 K+ to the cytoplasm
releases 3 K+ to the ECF
releases 1 Na+ to the ECF and 1 K+ to the cytoplasm

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

Conclusion/Synthesis: Resting Membrane Potential, Part I

K+ concentration is higher in a cell (140 mM) than out (5 mM); Na+ concentration is higher out (140 mM) than in (15 mM). At rest, K+ passively leaves the cell via K+ leakage channels, (negative membrane potential (-90 mV)), and Na+ passively enters via a few Na+ leakage channels (in combination with K+ leakage = less negative potential (-70 mV)). Na+-K+ pumps transport Na+ out (3 Na+ ions/turn) and K+ in (2 K+ ions/turn) to actively maintain the resting membrane concentration gradients of Na+ and K+ (70 mV).
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?

The cell is becoming depleted of Na+.
The cell is becoming depleted of K+.
The cell’s Na+-K+ ATPase pumps have stopped functioning.
The cell’s K+ leak channels have stopped functioning.
The cell’s Na+ leak channels have stopped functioning.

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

Conclusion/Synthesis: Resting Membrane Potential, Part II
Cl− is a common, negatively charged extracellular ion. Predict the effect on the RMP if many Cl− gated channels are suddenly opened.

The RMP would become more positive.
There would be no change in the RMP.
A more negative RMP would result.
The membrane would become hypopolarized or have less charge separation across the membrane.

A more negative RMP would result.