Deck 7: Nerve Cells and Electrical Signaling

Question 1

Which of the following is the correct term for the movement of an electrical charge across a membrane?

A) current
B) capacitance
C) transistor
D) potential difference
E) resistance

Answer 1

A

Question 2

The central nervous system, which is composed of the brain and spinal cord, receives and processes information from both the external environment, known as information and, the internal
Environment, which refers to

A) peripheral : somatic
B) sensory : visceral
C) somatic : autonomic
D) special : somatic
E) somatic : visceral

Answer 2

B

Question 3

An action potential originates at the .

A) dendrite : axon hillock
B) axon hillock : dendrite
C) dendrite : axon terminal
D) axon terminal : axon hillock
E) axon hillock : axon terminal

Answer 3

E

Question 4

What type of ion channels in the membrane of neurons open or close in response to a neurotransmitter binding to its receptor?

A) potential -gated channels
B) leak channels
C) synaptic channels
D) voltage -gated channels
E) ligand -gated channels

Question 5

What two divisions of the autonomic nervous system have opposite effects on the organs they innervate?

A) afferent and efferent
B) somatic and motor
C) peripheral and central
D) somatic and enteric
E) parasympathetic and sympathetic

Question 6

Which of the following best describes the function of the myelin sheath?

A) increase a membrane's ion permeability
B) reduce a membrane's ion permeability
C) increase leakage of ions across the membrane
D) decrease ion permeability in the nodes of Ranvier
E) decrease axonal conduction velocity

Question 7

Most neurons have a resting membrane potential of

A) +100 mV.
B) -55 mV.
C) +30 mV.
D) -70 mV.
E) -5 mV.

Question 8

In a neuron, where are voltage -gated calcium channels located?

A) axon hillock
B) axon terminal
C) dendrites
D) axon
E) soma

Question 9

A group of nerve cell bodies in the peripheral nervous system are referred to as

A) pathways.
B) commissures.
C) nuclei.
D) ganglia.
E) tracts.

Question 10

What functional class of neurons accounts for 99 percent of the neurons in the body processing sensory information and carrying out complex functions?

A) bipolar
B) efferent
C) visceral
D) afferent
E) interneurons

Question 11

branch from the cell body and receive input from other neurons at specialized junctions called .

A) Dendrites : cell bodies
B) Axon hillocks : axon terminals
C) Dendrites : synapses
D) Dendrites : axon terminals
E) Somas : synapses

Question 12

Which of the following accurately describes afferent neurons?

A) They are typically multipolar neurons.
B) They are the most abundant class of neurons.
C) They transmit information from the periphery to the CNS.
D) The cell body is located in the ventral horn of the spinal cord.
E) They transmit information from the CNS to the periphery.

Question 13

In a neuron, where is the greatest concentration of voltage -gated sodium and voltage -gated potassium channels?

A) axon
B) soma
C) axon terminal
D) axon hillock
E) dendrites

Question 14

The movement of synaptic vesicles to the end of the axon terminal involves what type of transport?

A) retrograde
B) pinocytosis
C) receptor -mediated
D) passive
E) anterograde

Question 15

What type of ion channels in the membrane of neurons allows ions to move across the membrane at rest and thereby contribute to resting membrane potential?

A) leak channels
B) resting channels
C) potential -gated channels
D) ligand -gated channels
E) voltage -gated channels

Question 16

On what portion of the neuron do action potentials propagate?

A) soma
B) dendrite
C) nucleus
D) cell body
E) axon

Question 17

What type of cell enhances the velocity of electrical transmission of an action potential along an axon in the central nervous system?

A) astrocyte
B) Schwann cell
C) ependymal cell
D) oligodendrocyte
E) microglia

Question 18

What is the functional unit of the nervous system?

A) neurons
B) the brain
C) axons
D) the central nervous system
E) glial cells

Question 19

What is the structural classification of a neuron composed of a single axon and a number of dendritic projections from the nerve cell body?

A) multipolar
B) pseudo -unipolar
C) unipolar
D) bipolar
E) polar

Question 20

In the peripheral nervous system, _ neurons carry sensory and visceral information to the central nervous system, and neurons leave the central nervous system and innervate
Organs, which are usually muscles or glands.

A) somatic : sensory
B) afferent : efferent
C) efferent : afferent
D) sympathetic : parasympathetic
E) sensory : somatic

Question 21

A change in a cell's membrane potential, such that the inside of the cell becomes more positive, is referred to as a whereas if it becomes more negative it is referred to as .

A) depolarization : hyperpolarization
B) hypopolarization : repolarization
C) repolarization : resting membrane potential
D) polarization : depolarization
E) hyperpolarization : depolarization

Question 22

The maintains the resting membrane potential.

A) equilibrium potential
B) Na⁺/Ca²⁺ exchanger
C) action potential
D) Na⁺/H⁺ antiporter
E) Na⁺/K⁺ pump

Question 23

What equation is used to calculate the membrane potential based on ion concentration gradients and permeabilities?

A) Nernst equation
B) GHK equation
C) Fick's equation
D) NAD equation
E) None of the answers is correct.

Question 24

A(n) is a subthreshold change in membrane potential within the cell body that decays as it travels away from its point of origin.

A) action potential
B) hyperpolarization
C) polarization
D) depolarization
E) graded potential

Question 25

When a weak stimulus is applied in rapid succession, it will often reach threshold due to

A) voltage potential.
B) spatial summation.
C) temporal summation.
D) excitatory summation.
E) inhibitory summation.

Question 26

The fact that a cell has an electrical potential difference across its membrane makes that cell

A) repolarized.
B) polarized.
C) polar.
D) hyperpolarized.
E) depolarized.

Question 27

The opening of sodium channels causes a rapid membrane.

A) efflux : depolarizes
B) influx : depolarizes
C) efflux : hyperpolarizes
D) influx : repolarizes
E) influx : hyperpolarizes

Question 28

Which of the following determines the resistance to an ion's movement across a membrane?

A) ion channels within the membrane
B) the ions present on either side of the membrane
C) the resting membrane potential
D) receptors on the cell membrane
E) enzymes on the surface of the cell membrane

Question 29

Which statement best describes how graded potentials determine whether an action potential will be generated or not?

A) when electrotonic conduction occurs within the soma of the neuron
B) when sodium enters the soma of a cell
C) when an excitatory depolarization reaches threshold
D) when the axon hillock is repolarized
E) when the neuron is hyperpolarized

Question 30

At the resting membrane potential, the membrane is most permeable to the cell due to its electrochemical gradient.

A) chloride : into
B) potassium : into
C) sodium : out of
D) sodium : into
E) potassium : out of

Question 31

At the resting membrane potential, the electrochemical gradient for sodium across the membrane is such that the net flux for sodium movement is directed , thereby causing the cell's
Membrane potential to become more .

A) inward : positive
B) at equilibrium : positive
C) outward : negative
D) outward : positive
E) inward : negative

Question 32

Which of the following is an example of spatial summation?

A) Two action potentials occur at the same time and sum.
B) A neuron sends out information through collaterals to several target cells.
C) Two stimuli from two sources produce graded potentials on the same neuron at the same time such that the two potentials sum.
D) Two rapid stimuli from the same source produce graded potentials on the neurons that sum.
E) An action potential occurs at the same time as a graded potential, and they sum.

Question 33

Which of the following changes in membrane potential is considered excitatory?

A) hyperpolarization only
B) depolarization only
C) repolarization only
D) both hyperpolarization and depolarization
E) both hyperpolarization and repolarization

Question 34

What is the inverse of resistance?

A) flux
B) current
C) conductance
D) voltage
E) impedance

Question 35

If the graded potential remains above threshold once it reaches the will be generated.

A) axon hillock
B) dendrite
C) cell body
D) nucleus
E) axon

Question 36

Which of the following best describes the electrochemical forces acting on sodium and potassium ions at the resting membrane potential?

A) Forces on both sodium and potassium ions are to move out of the cell.
B) The force on sodium ions is to move into the cell, and the force on potassium ions is to move out of the cell.
C) Forces on both sodium and potassium ions are to move into the cell.
D) The force on sodium ions is to move out of the cell, and the force on potassium ions is to move into the cell.
E) There is no force on either ion to move.

Question 37

What determines the strength of a graded potential?

A) the amount of voltage -gated channels in the neuron
B) the size of the stimulus
C) the amount of cytoplasmic resistance within the soma of the neuron
D) the amount of leak channels open in the neuron
E) the diameter of the axon

Question 38

The direction of change in membrane potential, in response to a stimulus that initiates a graded potential, is dependent upon

A) that membrane's threshold potential.
B) the gating of potassium channels only.
C) the changes in ion concentration across the membrane.
D) the ion channels that are opened or closed.
E) the gating of sodium channels only.

Question 39

If the soma of a neuron became more permeable to potassium, which statement below best describes the graded potential that would be generated in the soma?

A) Potassium would leave the cell, causing the membrane to hyperpolarize.
B) Potassium is a cation; therefore, it would cause an excitatory depolarization.
C) Potassium is an inhibitory second messenger; therefore, it would cause amplification of the graded potential.
D) Potassium would reach its equilibrium potential and the voltage inside the cell would not change.
E) Potassium would enter the cell, causing the membrane to depolarize and reach threshold.

Question 40

Saxitoxin (STX) is the most well -known paralytic shellfish toxin caused by the phenomenon known as "red tide." Which statement below best describes why this neurotoxin causes paralysis?

A) It acts by blocking voltage -gated sodium channels which are needed to generate an action potential.
B) It acts on the hypothalamus of the brain, shutting down all neurological functions.
C) It prevents the synaptic vesicles from migrating to the axon terminal; therefore, no action potentials are generated.
D) It blocks ligand -gated channels on the postsynaptic membrane, which blocks signals leaving the central nervous system.
E) It acts on the potassium channels within a neuron, hyperpolarizing the cell membrane; therefore, no action potential can be generated.

Question 41

During which of the following states are the majority of voltage -gated sodium channels closed and incapable of opening?

A) during the absolute refractory period
B) during the after -hyperpolarization
C) during depolarization
D) during the relative refractory period
E) at the resting membrane potential

Question 42

The depolarization phase of the action potential is generated by a rapid

A) closure of sodium channels.
B) closure of potassium channels.
C) opening of chloride channels.
D) opening of potassium channels.
E) opening of sodium channels.

Question 43

is the mechanism by which action potentials are propagated in unmyelinated axons.

A) The regenerative mechanism
B) The all -or -none principle
C) Temporal summation
D) Electrotonic conduction
E) After -hyperpolarization

Question 44

Which statement below best describes why action potentials travel in only one direction?

A) The diameter of the axon explains this.
B) The all -or -none principle explains this.
C) They have a refractory period.
D) They have myelinated axons.
E) Only sodium -and potassium -gated channels are found on the axon.

Question 45

The repolarization phase of action potentials in neurons is due primarily to

A) increased activity of the Na⁺/K⁺ pump.
B) sodium flow out of the cell.
C) sodium flow into the cell.
D) potassium flow into the cell.
E) potassium flow out of the cell.

Question 46

The magnitude of depolarization at the peak of an action potential is dependent on what factor?

A) the length of the refractory period
B) the size of the stimulus
C) the concentration of sodium and potassium ions
D) the strength of the electrochemical gradient for sodium and potassium ions relative to their permeability to these ions
E) the size of the graded potential

Question 47

Toward the end of the relative refractory period, the continued decrease in stimulus intensity required to initiate an action potential is caused by

A) the number of sodium channels whose inactivation gate has not opened.
B) increased potassium permeability.
C) decreased sodium permeability.
D) closure of the sodium activation gate.
E) decreased potassium permeability.

Question 48

The jumping of an action potential from node -to -node is called

A) propagation.
B) nodal conduction.
C) electrotonic conduction.
D) nodal propagation.
E) saltatory conduction.

Question 49

In order to generate an action potential, the magnitude of the inward sodium current must be large enough to overcome which of the following?

A) outward sodium current
B) outward calcium current
C) inward potassium current
D) inward chloride current
E) outward potassium current

Question 50

Which of the following axons would have the fastest conduction velocity?

A) diameter = 5 microns, unmyelinated
B) diameter = 20 microns, myelinated
C) diameter = 5 microns, myelinated
D) diameter = 1 micron, myelinated
E) diameter = 20 microns, unmyelinated

Question 51

The depolarization of the membrane due to a stimulus is a regenerative mechanism meaning that, once sodium gates begin to open, even more sodium gates will be activated leading to a larger inflow of sodium ions and more depolarization until it is terminated when sodium gates close. This is an example of

A) inhibitory graded potentials.
B) negative feedback.
C) excitatory graded potentials.
D) positive feedback.
E) electrotonic conduction.

Question 52

As an action potential is propagated away from the axon hillock, why does propagation continue in one direction?

A) The region just in front of the action potential is in the absolute refractory period.
B) The region just behind the action potential is in the absolute refractory period.
C) The region just behind the action potential is in the relative refractory period.
D) The region just in front of the action potential is in the relative refractory period.
E) They will travel the path of least resistance.

Question 53

How can action potentials relay information about the intensity of a stimulus, such as distinguishing between a loud and soft sound?

A) due to summation of several action potentials
B) due to the frequency of action potentials
C) due to electrotonic conduction
D) due to the magnitude of action potentials
E) due to the decremental properties of graded potentials

Question 54

The repolarization phase of the action potential in a neuron is driven by the

A) closure of potassium channels.
B) opening of calcium channels.
C) opening of sodium channels.
D) opening of sodium channels and closure of potassium channels.
E) closure of sodium channels and opening of potassium channels.

Question 55

In myelinated axons, sodium and potassium channels would be concentrated in what area?

A) nucleus
B) axon hillock
C) nodes of Ranvier
D) axon terminal
E) dendrites

Question 56

What limits the maximum number of action potentials on an axon?

A) the relative refractory period
B) the diameter of the axon
C) the absolute refractory period
D) whether the axon is myelinated or not
E) the concentration of sodium within the cytoplasm of the cell

Question 57

For an unmyelinated axon, conduction velocity is primarily determined by the

A) type of potassium channel activated.
B) type of sodium channel activated.
C) diameter of the axon.
D) number of ion channels present on the membrane.
E) permeability of the axonal membrane.

Question 58

A subthreshold stimulus will not generate an action potential whereas a suprathreshold stimulus does generate an action potential. This is an example of

A) a refractory period.
B) electrotonic conduction.
C) the all -or -none principle.
D) positive feedback.
E) negative feedback.

Question 59

In myelinated nerve fibers, where do action potentials occur?

A) underlying myelin sheath
B) nodes of Ranvier
C) cell body
D) oligodendrocyte
E) Schwann cell

Question 60

The all -or -none principle, associated with the action potential, states that

A) following an action potential, the membrane will be repolarized by the opening of a potassium channel.
B) all of the action potentials will be generated from the axon hillock.
C) the positive feedback loop for the sodium channel is terminated by the inactivation gate.
D) once membrane potential reaches threshold, an action potential will be generated and that action potential will always be the same magnitude.
E) there is a positive feedback loop for sodium channels that results in a rapid membrane depolarization.

Question 61

Which of the following potentials has an all -or -none response?

A) graded potentials
B) threshold potentials
C) action potentials
D) both graded potentials and action potentials
E) neither graded potentials nor action potentials

Question 62

What portion of the peripheral nervous system communicates to effector organs?

A) spinothalmic tract
B) efferent nervous system
C) central nervous system
D) afferent nervous system
E) enteric nervous system

Question 63

The brain and spinal cord are part of which of the following branches of the nervous system?

A) central nervous system
B) enteric nervous system
C) efferent nervous system
D) somatic nervous system
E) afferent nervous system

Question 64

What portion of the efferent branch of the nervous system communicates to glands and cardiac muscle?

A) enteric nervous system
B) somatic nervous system
C) afferent nervous system
D) central nervous system
E) autonomic nervous system

Question 65

Which of the following potentials can sum?

A) graded potentials
B) threshold potentials
C) action potentials
D) both graded potentials and action potentials
E) neither graded potentials nor action potentials

Question 66

Which of the following potentials is a result of opening or closing of ion channels?

A) graded potentials
B) threshold potentials
C) action potentials
D) both graded potentials and action potentials
E) neither graded potentials nor action potentials

Question 67

What portion of the efferent nervous system communicates with skeletal muscle?

A) central nervous system
B) autonomic nervous system
C) somatic nervous system
D) afferent nervous system
E) enteric nervous system

Question 68

Which statement best describes how local anesthetics such as Novocaine work in numbing neurons?

A) by blocking voltage -gated potassium channels
B) by binding to the enzyme sodiumase
C) by making the cell membrane more permeable to potassium
D) by making the cell membrane more permeable to sodium
E) by blocking voltage -gated sodium channels

Question 69

What nervous system is found in the intestinal tract?

A) afferent nervous system
B) somatic nervous system
C) efferent nervous system
D) enteric nervous system
E) central nervous system

Question 70

Which statement best describes the event indicated by the letter "C" in Figure 7.1 and how that event is initiated?

A) It is an excitatory potential that causes the relative refractory period.
B) It is a suprathreshold graded potential resulting from the opening and closing of sodium and potassium channels.
C) It is a hyperpolarization of the membrane due to the outward movement of potassium ions.
D) It is a subthreshold graded potential resulting from the opening of sodium channels, closure of potassium channels, or opening of ion channels for sodium and potassium.
E) It is a suprathreshold depolarization representing an action potential.

Question 71

Which of the following are common symptoms of peripheral neuropathy?

A) confusion, excessive thirst, dehydration, and frequent urination
B) numbness, tingling sensation, or pain in the hands and feet
C) dizziness, diarrhea, indigestion and impotence
D) numbness of the tongue, jaw, and ears
E) increased heart rate, excessive sweating, and red skin

Question 72

Identify the type of summation that is occurring in Figure 7.1 where "S" refers to a stimulus from one source measured in the postsynaptic membrane.

A) spatial
B) multiplier
C) temporal
D) suprathreshold
E) subthreshold

Question 73

What portion of the peripheral nervous system transmits information from sensory receptors to the central nervous system?

A) efferent nervous system
B) autonomic nervous system
C) somatic nervous system
D) afferent nervous system
E) central nervous system

Question 74

What portion of the nervous system provides communication between peripheral organs and the brain and spinal cord?

A) peripheral nervous system
B) somatic nervous system
C) efferent nervous system
D) afferent nervous system
E) central nervous system

Question 75

Which of the following potentials are affected by refractory periods?

A) graded potentials
B) threshold potentials
C) action potentials
D) both graded potentials and action potentials
E) neither graded potentials nor action potentials

Question 76

Which of the following potentials dissipate in size as the potential moves away from the site of initiation?

A) graded potentials
B) threshold potentials
C) action potentials
D) both graded potentials and action potentials
E) neither graded potentials nor action potentials

Question 77

Which statement best describes the events responsible for the phase represented by the letter "B" in Figure 7.1?

A) the opening of sodium channels
B) the opening and closing of sodium channels
C) the opening of potassium channels
D) the closing of sodium channels and the opening of potassium channels
E) the opening of potassium channels and the closing of sodium channels

Question 78

Why do the distributions of sodium and potassium ions across the plasma membrane of neurons not change appreciably, even following hundreds of action potentials?

A) The movement of sodium and potassium ions that occurs during an action potential is countered by the passive movement of these ions during the repolarization phase.
B) The movement of sodium and potassium ions that occurs during an action potential is countered by the passive movement of these ions during the after -hyperpolarization.
C) The movement of sodium and potassium ions that occurs during an action potential is countered by counter -transport of potassium with sodium during rest.
D) The movement of sodium and potassium ions that occurs during an action potential is countered by the active transport of these ions by the Na⁺/K⁺ pump.
E) The movement of sodium and potassium ions that occurs during an action potential is countered by the passive leak of these ions when a neuron is at rest.

Question 79

Which statement best describes the events responsible for the phase represented by the letter "A" in Figure 7.1?

A) the opening of sodium channels
B) the opening and closing of sodium channels
C) the opening of potassium channels
D) the closing of sodium channels and the opening of potassium channels
E) the opening of potassium channels and the closing of sodium channels

Question 80

What percentage of people with diabetes develop peripheral neuropathy?

A) 50 percent
B) 10 percent
C) 20 percent
D) 30 percent
E) 5 percent