Deck 7: Nerve Cells and Electrical Signaling

Question 1

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 information.

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

Answer 1

D

Question 2

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

Answer 2

A

Question 3

What is the inverse of resistance?

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

Answer 3

B

Question 4

What is the most common neuronal cell type?

A)afferent neuron
B)interneuron
C)bipolar neuron
D)pseudo- unipolar neuron
E)efferent neuron

Question 5

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

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

Question 6

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

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

Question 7

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 8

The _ maintains the resting membrane potential.

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

Question 9

During the rapid depolarization phase of an action potential, the plasma membrane is more permeable to which of the following ions?

A)sodium (Na+)
B)potassium (K+)
C)chloride (Cl- )
D)calcium (Ca++)
E)phosphate (PO4- )

Question 10

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

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

Question 11

Most neurons have a resting membrane potential of

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

Question 12

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

Question 13

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

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

Question 14

What type of ion channels is located along the axon?

A)voltage- gated channels
B)ligand- gated channels
C)mechanical channels
D)propagation channels
E)initiation channels

Question 15

Increased permeability to what ion is responsible for the relative refractory period?

A)sodium (Na+)
B)potassium (K+)
C)chloride (Cl- )
D)calcium (Ca++)
E)phosphate (PO4- )

Question 16

What is the passive spread of current along a membrane called?

A)electrotonic conduction
B)action potential
C)graded potential
D)refractory period
E)resistance

Question 17

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

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

Question 18

Which of the following accurately describes afferent neurons?

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

Question 19

In myelinated nerve fibers, where do action potentials occur?

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

Question 20

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

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

Question 21

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

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

Question 22

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 active transport of these ions by the Na+/K+ pump.
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 repolarization phase.
C)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.
D)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.
E)The movement of sodium and potassium ions that occurs during an action potential is countered by counter- transport of potassium with sodium during rest.

Question 23

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 24

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

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

Question 25

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

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

Question 26

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 27

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

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

Question 28

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

Question 29

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

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

Question 30

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

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

Question 31

The opening of sodium channels causes a rapid of sodium that the neuron's membrane.

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

Question 32

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

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

Question 33

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 out of the cell, and the force on potassium ions is to move into 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 into the cell, and the force on potassium ions is to move out of the cell.
E)There is no force on either ion to move.

Question 34

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

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

Question 35

What is the level of membrane depolarization required to induce the sodium channel's positive feedback loop called?

A)suprathreshold
B)axon hillock
C)threshold
D)axon terminal
E)subthreshold

Question 36

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

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

Question 37

Which type of glial cell provides the myelin sheath for many axons in the central nervous system?

A)ependymal cells
B)astrocytes
C)Schwann cell
D)microglia
E)oligodendrocytes

Question 38

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

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

Question 39

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 40

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

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

Question 41

On what portion of the neuron do action potentials propagate?

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

Question 42

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)enzymes on the surface of the cell membrane
D)the resting membrane potential
E)receptors on the cell membrane

Question 43

What is the only glial cell found outside of the central nervous system?

A)oligodendrocytes
B)Schwann cell
C)microglia
D)astrocytes
E)ependymal cells

Question 44

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

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

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

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

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

Question 47

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

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

Question 48

At rest, the plasma membrane is more permeable to which of the following ions?

A)sodium (Na+)
B)potassium (K+)
C)chloride (Cl- )
D)calcium (Ca++)
E)phosphate (PO4- )

Question 49

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

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

Question 50

Which of the following potentials can reach or exceed the sodium equilibrium potential?

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

Question 51

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

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

Question 52

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

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

Question 53

The fact that the opening of some sodium channels can induce several other sodium channels to open describes the property of these channels.

A)suprathreshold
B)ligand
C)all- or- none principle
D)regenerative
E)refractory

Question 54

What percentage of people with diabetes develop peripheral neuropathy?

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

Question 55

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

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

Question 56

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 potassium current
C)outward calcium current
D)inward potassium current
E)inward chloride current

Question 57

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

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

Question 58

The resting membrane potential is close to the equilibrium potential of which of the following ions?

A)sodium (Na+)
B)potassium (K+)
C)chloride (Cl- )
D)calcium (Ca++)
E)phosphate (PO4- )

Question 59

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

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

Question 60

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

Question 61

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

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

Question 62

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

Question 63

Information gathered about our internal environment (i.e., fullness of the stomach, blood pressure, etc.)is called information.

A)efferent
B)visceral
C)sensory
D)somatic
E)afferent

Question 64

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

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

Question 65

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

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

Question 66

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 67

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 68

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

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

Question 69

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

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

Question 70

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

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

Question 71

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

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

Question 72

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 73

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

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

Question 74

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 75

An action potential originates at the _ and travels along the axon until it reaches the .

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

Question 76

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

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

Question 77

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

Question 78

In the peripheral nervous system, myelin is formed by . In the central nervous system, myelin is formed by _ .

A)Schwann cells : oligodendrocytes
B)Schwann cells : astrocytes
C)Schwann cells : microglial cells
D)oligodendrocytes : Schwann cells

Question 79

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

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

Question 80

What nervous system is found in the intestinal tract?

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