Deck 4: Principles of Neural and Hormonal Communication

Question 1

Myelinated axons conduct impulses much faster because

A) The myelin insulates the axon.
B) Channels only have to open at the nodes.
C) Voltage is not lost along myelinated areas.
D) Saltatory conduction occurs.
E) All of these.

Answer 1

E

Question 2

A change in a membrane potential from -70 mV to -60mV is an example of

A) depolarization
B) hyperpolarization
C) polarization
D) repolarization
E) zero potential

Answer 2

A

Question 3

Graded potentials

A) are local changes in membrane potential that occur in varying degrees of magnitude
B) serve as short-distance signals
C) serve as long-distance signals
D) are local changes in membrane potential that occur in varying degrees of magnitude, and serve as short-distance signals
E) are local changes in membrane potential that occur in varying degrees of magnitude, and serve as long-distance signals

Answer 3

D

Question 4

When chemically-gated Na⁺ channels open, the membrane

A) hyperpolarizes
B) repolarizes
C) depolarizes
D) becomes more negative
E) is inhibited

Question 5

When an excitatory neurotransmitter binds to a postsynaptic neuron

A) Voltage-gated Na⁺ channels open.
B) Voltage-gated K⁺ channels open.
C) Chemically-gated Na⁺ channels open.
D) Voltage-gated Cl^- channels open.
E) Chemically-gated Cl^- channels open.

Question 6

Which statement is not accurate about the absolute refractory period?

A) Another stimulus, regardless of its strength, cannot initiate another action potential during this period.
B) During this period, voltage-gated Na⁺ channels open, then close but are inactivated.
C) Immediately following this period, the membrane can experience another action potential if the stimulus is strong enough.
D) This period occurs during the after hyperpolarization phase of the action potential.
E) This period ensures a unidirectional spread of the action potential down a nerve fiber.

Question 7

During the rising phase of the action potential:

A) P_K+ is much greater than P_Na+.
B) P_Na+ is much greater than P_K+.
C) P_K+ is the same as P Na⁺.
D) Na⁺ efflux occurs.
E) P_Na+ is much greater than P_K+, and Na⁺ efflux occurs.

Question 8

Which of the following is responsible for the falling phase of an action potential?

A) opening of Na⁺ gates
B) Na⁺-K⁺ pump restoring the ions to their original locations
C) greatly increased permeability to Na⁺
D) ATP-ase destroying the energy supply that was maintaining the action potential at its peak
E) none of these

Question 9

A threshold potential is

A) the potential achieved when two opposing forces acting upon an ion (concentration and electrical gradients) achieve a state of equilibrium
B) the peak potential achieved during an action potential
C) the point at which there is an explosive increase in Na⁺ or Ca²⁺ permeability
D) the potential at which K⁺ permeability increases
E) always a positive potential

Question 10

The falling phase of the action potential is due to

A) calcium equilibrium
B) potassium efflux
C) potassium influx
D) sodium efflux
E) sodium influx

Question 11

When a membrane is stimulated due to opening of either chemically-gated Na⁺ or Cl^- channels:

A) An impulse is propagated.
B) A graded potential is established.
C) An action potential is established.
D) The voltage becomes more negative.
E) Threshold is reached.

Question 12

Which term best describes an excitable cell when a resting membrane potential is present?

A) polarized
B) depolarized
C) hyperpolarized
D) repolarized
E) nonpolarized

Question 13

The negative charge established along a nerve cell membrane is due to

A) movement of Na⁺ into the cell
B) movement of proteins out of the cell
C) higher permeability of K⁺ relative to Na⁺
D) intracellular protein anions
E) higher permeability of K⁺ relative to Na⁺ and intracellular protein anions

Question 14

The rising phase of the action potential is due to

A) calcium equilibrium
B) potassium efflux
C) potassium influx
D) sodium efflux
E) sodium influx

Question 15

Because of the presence of both activation and inactivation gates, voltage-gated Na⁺ channels can

A) be closed but capable of opening
B) be activated
C) be closed and not capable of opening
D) all of these
E) none of these

Question 16

An action potential on a neuron develops when

A) threshold voltage is reached on an axon
B) voltage-gated Na⁺ channels open
C) spatial and/or temporal summation of graded potentials occurs to a great enough degree
D) the axon hillock reaches threshold
E) all of these

Question 17

A change in a membrane potential from +30 mV to -70 mV is an example of

A) depolarization
B) hyperpolarization
C) polarization
D) repolarization
E) zero potential

Question 18

At the peak of an action potential:

A) The electrical gradient for Na⁺ causes a net movement of this ion out of the cell.
B) The concentration gradient for K⁺ tends to move this ion out of the cell.
C) K⁺ permeability greatly increases.
D) All of these.
E) The concentration gradient for K⁺ tends to move this ion out of the cell, and K⁺ permeability greatly increases.

Question 19

Which of the following is not a graded potential?

A) end-plate potential
B) action potential
C) slow-wave potential
D) receptor potential
E) postsynaptic potential

Question 20

The cells of excitable and nonexcitable tissues share

A) a threshold potential
B) a resting membrane potential
C) an ability to open the Na⁺ gates
D) all of these
E) none of these

Question 21

Conduction by local current flow

A) occurs in unmyelinated fibers
B) is faster than propagation of an action potential in myelinated fibers because myelin acts as an insulator to slow down the impulse
C) involves current flowing between active and adjacent inactive areas, thereby bringing the inactive areas to threshold
D) all of these
E) occurs in unmyelinated fibers and involves current flowing between active and adjacent inactive areas, thereby bringing the inactive areas to threshold

Question 22

The membrane is more permeable to K⁺ than to Na⁺

A) at resting potential
B) during the rising phase of an action potential
C) during the rising phase of a graded potential
D) at resting potential and during the rising phase of an action potential
E) at resting potential and during the rising phase of a graded potential

Question 23

Which statement is incorrect?

A) A local current can occur in myelinated nerve fibers.
B) A local current flow from an active to an adjacent inactive area decreases the potential in the inactive area to threshold.
C) Contiguous conduction occurs along Schwann cells that surround myelinated nerve fibers.
D) Saltatory conduction is faster than contiguous conduction.
E) Conduction by local current flow is the method of propagation in unmyelinated fibers.

Question 24

The trigger zone of a neuron

A) is located where the axon connects to the neuron's cell body
B) is located in the axon terminal
C) contains only chemically gated channels
D) conducts graded potentials to the axon
E) contains only chemically gated channels and conducts graded potentials to the axon

Question 25

At an excitatory synapse, an action potential in the presynaptic neuron increases the

A) membrane potential of the postsynaptic cell membrane
B) permeability of the postsynaptic cell to both Na⁺
C) permeability of the postsynaptic cell to Cl^-
D) all of these
E) membrane potential of the postsynaptic cell membrane and permeability of the postsynaptic cell to both Na⁺

Question 26

Saltatory conduction

A) occurs in unmyelinated nerve fibers
B) is slower than conduction by local current flow because the myelin acts as an insulator to slow the impulse down
C) involves the impulse jumping from one node of Ranvier to the adjacent node
D) refers to the action potential spreading from one Schwann cell to the adjacent Schwann cell
E) more than one of these

Question 27

If a neuron were experimentally stimulated at both ends simultaneously:

A) The action potentials would pass in the middle and travel to the opposite ends.
B) The action potentials would meet in the middle and then be propagated back to their starting positions.
C) The action potentials would stop as they met in the middle.
D) The strongest action potential would override the weaker action potential.
E) Summation would occur when the action potentials met in the middle, resulting in a larger action potential.

Question 28

Permeability of which ion is affected by a positive feedback mechanism once threshold is reached?

A) sodium
B) potassium
C) calcium
D) chloride
E) protein

Question 29

The relative refractory period occurs after the action potential is complete because of the

A) lingering inactivation of the voltage-gated Na⁺ channels
B) slowness of the voltage-gated K⁺ channels
C) action of the sodium-potassium pumps
D) lingering inactivation of the voltage-gated Na⁺ channels and slowness of the voltage-gated K⁺ channels
E) slowness of the voltage-gated K⁺ channels and action of the sodium-potassium pumps

Question 30

At an inhibitory synapse, the postsynaptic membrane experiences

A) an increase in permeability to both Na⁺ and K⁺
B) an increase in membrane potential
C) hyperpolarization
D) an increase in membrane potential and hyperpolarization
E) all of these

Question 31

During the peak of the action potential, the membrane becomes most permeable to

A) sodium
B) potassium
C) calcium
D) chloride
E) protein

Question 32

Select the incorrect statement about the action potential.

A) It has an all-or-none characteristic.
B) It has a refractory period.
C) It is triggered by depolarization to threshold.
D) It occurs along a plasma membrane.
E) It speeds up transmission by summation.

Question 33

When the membrane potential is +15 mV, that portion of the membrane

A) is in the normal resting state
B) has a more positive outside border
C) is more permeable to Ca²⁺ than normal
D) is in the after hyperpolarization phase of an action potential
E) has a more positive outside border and is more permeable to Ca²⁺ than normal

Question 34

Spatial summation occurs in a postsynaptic neuron

A) when several EPSPs from a single presynaptic input sum to reach threshold
B) when EPSPs from several presynaptic inputs sum to reach threshold
C) upon simultaneous interaction of an EPSP and an IPSP
D) when several IPSPs from a single presynaptic input sum to hyperpolarize the membrane
E) none of these

Question 35

If neuron Z is repeatedly stimulated very rapidly, what change would you expect in the postsynaptic neuron?

A) several simultaneous action potentials
B) movement farther away from threshold
C) spatial summation of EPSPs
D) movement farther away from threshold and spatial summation of EPSPs
E) none of these

Question 36

Which statement about graded potentials is false?

A) They are decremental.
B) They travel only short distances.
C) They are self-propagating.
D) They may contribute to the development of an action potential.
E) They travel in both directions along the membrane.

Question 37

The period following an action potential during which a membrane cannot experience another action potential

A) is the absolute refractory period
B) occurs during the time after the Na⁺ gates have opened until they are restored to their "closed but capable of opening" conformation
C) prevents the action potential from spreading back over the part of the membrane where the impulse has just passed
D) is the absolute refractory period and occurs during the time after the Na⁺ gates have opened until they are restored to their "closed but capable of opening" conformation
E) all of these

Question 38

Temporal summation on a postsynaptic neuron takes place when

A) a single presynaptic input causes two EPSPs to develop in rapid succession
B) an EPSP and an IPSP occur simultaneously and cancel each other out
C) two EPSPs develop simultaneously from different presynaptic inputs
D) two action potentials from two presynaptic inputs causes two action potentials to develop
E) none of these

Question 39

The absolute refractory period

A) prevents action potentials from spreading forward and backward
B) refers to a period when the membrane cannot undergo another action potential
C) is the time when channels opened during the action potential have not been restored to their "closed but capable of opening" conformation
D) places an upper limit on the frequency with which a neuron can conduct action potentials
E) refers to a period when the membrane cannot undergo another action potential and places an upper limit on the frequency with which a neuron can conduct action potentials

Question 40

What is responsible for development of the resting membrane potential?

A) leak channels
B) gated channels
C) ion pumps
D) leak channels and gated channels
E) leak channels and ion pumps

Question 41

Which statement about a graded potential is false?

A) It can be a depolarization.
B) It can be a hyperpolarization.
C) It can be summated.
D) It has a refractory period.
E) It occurs in a specialized area of the membrane.

Question 42

Neuron A and neuron B release a minimal amount of neurotransmitter simultaneously onto neuron C, causing neuron C to experience an action potential. This is an example of

A) temporal summation
B) spatial summation
C) convergence
D) temporal summation and convergence
E) spatial summation and convergence

Question 43

Which statement is correct?

A) In presynaptic inhibition, another neuron inhibits an excitatory presynaptic input.
B) An IPSP depresses information fed into the cell from an inhibitory presynaptic input.
C) Not all axon terminals of an inhibitory neuron release inhibitory neurotransmitter.
D) When presynaptic inhibition takes place, there is no change in presynaptic membrane potential.
E) An IPSP decreases the potential of the postsynaptic neuron.

Question 44

Select the last step for synaptic signaling when the action potential arrives at the axon terminal of a presynaptic neuron.

A) A neurotransmitter is released by exocytosis.
B) Calcium flows in the synaptic knob.
C) The neurotransmitter combines with protein receptor sites on the subsynaptic membrane.
D) The permeability is altered in a postsynaptic neuron.
E) None of these.

Question 45

Select the first step for synaptic signaling when the action potential arrives at the axon terminal of a presynaptic neuron.

A) A neurotransmitter is released by exocytosis.
B) Calcium flows into the synaptic knob.
C) The neurotransmitter combines with protein receptor sites on the subsynaptic membrane.
D) The permeability is altered in a postsynaptic neuron.
E) The neurotransmitter is synthesized.

Question 46

Select the normal direction for the movement of an action potential along part of a neuron.

A) axon hillock to cell body
B) axon terminal to collateral axon
C) axon to dendrite
D) cell body to receptor
E) dendrite to cell body

Question 47

In convergence:

A) Many presynaptic cells can synapse with a single postsynaptic cell.
B) An axon branches so that the activity in one neuron influences many other cells.
C) Many dendrites converge on the cell body.
D) All of these.
E) None of these.

Question 48

Sequence the following events correctly.

A) 1, 2, 3, 5, 4
B) 1, 4, 3, 2, 5
C) 2, 1, 5, 4, 3
D) 3, 1, 4, 5, 2
E) 5, 4, 3, 1, 2

Question 49

With presynaptic inhibition:

A) An IPSP occurs on the postsynaptic cell.
B) All excitatory information being fed into the cell is prevented.
C) The release of excitatory transmitter from a specific presynaptic excitatory input is depressed.
D) More than one of these.
E) None of these.

Question 50

The nodes of Ranvier are

A) action potential recordings
B) breaks in the myelin covering
C) spaces between neurons
D) specialized cells around axons
E) all of these, except action potential recordings

Question 51

The nucleus of a neuron is housed in the

A) axon
B) axon hillock
C) cell body
D) collaterals
E) dendrites

Question 52

An IPSP is

A) produced by increased Na⁺ permeability and K⁺ permeability
B) produced by increased K⁺ permeability or increased Cl^- permeability
C) a hyperpolarization of the presynaptic cell
D) produced by increased Na⁺ permeability and K⁺ permeability and a hyperpolarization of the presynaptic cell
E) produced by increased K⁺ permeability or increased Cl^- permeability and a hyperpolarization of the presynaptic cell.

Question 53

Drugs may influence synaptic transmission by

A) altering the formation of neurotransmitters
B) blocking neurotransmitter reuptake
C) blocking receptors
D) blocking channels
E) all of these

Question 54

Which channel type is sensitive to serotonin?

A) voltage-gated
B) chemically-gated
C) mechanically-gated
D) acoustically-gated
E) none of these

Question 55

Which statement is incorrect?

A) Inhibitory synapses cause postsynaptic hyperpolarization.
B) An inhibitory synapse may result in postsynaptic sodium channel opening.
C) Inhibitory synapse may result in increased postsynaptic potassium efflux.
D) An excitatory synapse causes depolarization of postsynaptic membranes.
E) An excitatory synapse increases sodium permeability.

Question 56

Select the neuropeptide.

A) acetylcholine
B) dopamine
C) epinephrine
D) cholecystokinin
E) glycine

Question 57

A hypothetical postsynaptic neuron has three presynaptic inputs¾X, Y, and Z. When X and Y are stimulated simultaneously, the postsynaptic neuron undergoes an action potential, yet when X and Z are stimulated simultaneously, there is no change in the postsynaptic neuron's potential. What can you tell about neurons Y and Z?

A) Y and Z are both excitatory.
B) Y and Z are both inhibitory.
C) Y is excitatory and Z is inhibitory.
D) Y is inhibitory and Z is excitatory.
E) Not enough information to answer.

Question 58

In divergence:

A) Many presynaptic neurons synapse with one postsynaptic cell.
B) Dendrites diverge from the cell body to contact many presynaptic neurons.
C) The action potential initiated in the axon diminishes as it spreads into the axon terminals.
D) An axon branches to synapse with many cells so that activity in one neuron influences the excitability of many other cells.
E) Many axons spread out from one cell body.

Question 59

Neuromodulators

A) bind to receptors at nonsynaptic sites
B) do not contribute directly to EPSPs
C) do not contribute directly to IPSPs
D) may influence neurotransmitter production
E) all of these

Question 60

Presynaptic facilitation results from

A) alteration of calcium permeability
B) continued generation of EPSPs
C) neuromodulator effects
D) increased neurotransmitter production
E) none of these

Question 61

Neuropeptides

A) are sometimes co-secreted along with classical neurotransmitters
B) are synthesized in the cytosol of the axon terminal
C) act at the subsynaptic membrane of the postsynaptic neuron
D) all of these
E) are sometimes co-secreted along with classical neurotransmitters and are synthesized in the cytosol of the axon terminal

Question 62

Action potentials can be summed.

Question 63

Threshold potential is the peak potential achieved during an action potential.

Question 64

After an action potential has occurred, there is more Na⁺ inside the cell than outside the cell (before any Na⁺-K⁺ pump activity has taken place).

Question 65

Nerve and muscle cells establish resting membrane potentials.

Question 66

During the resting potential, the membrane is more permeable to potassium ions than to sodium ions.

Question 67

For graded potentials, the magnitude of triggering is coded for in frequency rather than amplitude of depolarizations.

Question 68

For the following questions, assume a hypothetical postsynaptic neuron has three presynaptic inputs: neurons X, Y, and Z. Also, assume neuron Z is excitatory. If neurotransmitter from Y causes the membrane potential of the postsynaptic cell to decrease slightly, then the

A) synapse is excitatory
B) postsynaptic membrane's potential will be farther away from threshold
C) postsynaptic membrane could be excitatory or inhibitory
D) neurotransmitter from Y causes an IPSP on the presynaptic membrane
E) postsynaptic membrane's potential will be farther away from threshold, and the neurotransmitter from Y causes an IPSP on the presynaptic membrane

Question 69

For the following questions, assume a hypothetical postsynaptic neuron has three presynaptic inputs: neurons X, Y, and Z. Also, assume neuron Z is excitatory. If neurotransmitter from X causes a slight hyperpolarization of the postsynaptic cell, then the

A) synapse is excitatory
B) synapse is inhibitory
C) synapse could be excitatory or inhibitory
D) postsynaptic cell's membrane potential has decreased
E) synapse is excitatory and the postsynaptic cell's membrane potential has decreased

Question 70

Tetanus toxin

A) combines with glycine receptors, thus blocking the action of this inhibitory neurotransmitter
B) destroys dopamine in the region of the brain involved in controlling complex movements
C) prevents the release of GABA onto inputs terminating on neurons that supply skeletal muscles
D) promotes presynaptic facilitation
E) causes retrograde flow in axon

Question 71

For the following questions, assume a hypothetical postsynaptic neuron has three presynaptic inputs: neurons X, Y, and Z. Also, assume neuron Z is excitatory. If neurons Y and Z receive simultaneous stimulation, what change would you expect in the postsynaptic neuron?

A) a single EPSP
B) a single IPSP
C) temporal summation of EPSPs
D) spatial summation of EPSPs
E) an IPSP and EPSP would cancel each other out, so there would be essentially no change in potential in the postsynaptic neuron

Question 72

For the following questions, assume a hypothetical postsynaptic neuron has three presynaptic inputs: neurons X, Y, and Z. Also, assume neuron Z is excitatory. What changes would you expect at the postsynaptic neuron when neuron X is stimulated? (Remember that the postsynaptic neuron becomes hyperpolarized by neuron X.)

A) increased P_Na+ and P_K+
B) increased P_K+ or P_Cl-
C) increased P_A-
D) increased P_Ca2+
E) none of these

Question 73

A spike is another name for the axon of a neuron.

Question 74

The passive current flow of a graded potential fades quickly.

Question 75

The Na⁺ and K⁺ channels that open and close during an action potential are voltage-gated channels.

Question 76

For the following questions, assume a hypothetical postsynaptic neuron has three presynaptic inputs: neurons X, Y, and Z. Also, assume neuron Z is excitatory. If neurons X and Z receive simultaneous stimulation, what change would you expect in the postsynaptic neuron?

A) a single EPSP
B) a single IPSP
C) temporal summation of EPSPs
D) spatial summation of EPSPs
E) an IPSP and EPSP would cancel each other out, so there would be essentially no change in potential in the postsynaptic neuron

Question 77

In a graded potential, the direction of current flow is designated by the movement of positive charges.

Question 78

Action potentials may result from hyperpolarization or depolarization.

Question 79

For the following questions, assume a hypothetical postsynaptic neuron has three presynaptic inputs: neurons X, Y, and Z. Also, assume neuron Z is excitatory. What would you expect at the postsynaptic neuron when neuron Y is stimulated? (Remember that the postsynaptic neuron's membrane potential is decreased by neuron Y.)

A) increased P_Na+ and P_K+
B) increased P_K+ or P_Cl-
C) increased P_A-
D) increased P_Ca2+
E) none of these

Question 80

Schwann cells promote axonal growth, while oligodendrocytes inhibit it.