Chapter 11 Fundamental of Nervous System and Nervous Tissue (Mastering A&P)

Levels of organization in the nervous system

Which of the neuroglial cell types is the most abundant in the CNS?



A. Oligodendrocyte
B. Astrocyte
C. Microglia
D. Ependymal cells
E. Schwann Cells & Satellite cells

Where in the neuron is an action potential initially generated?

A. soma and dendrites
B. axon hillock
C. anywhere on the axon

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

A. chemically gated Na+ channels
B. voltage-gated Na+ channels
C. voltage-gated K+ channels
D. chemically gated K+ channels

The repolarization phase of an action potential results from

A. the opening of voltage-gated Na+ channels
B. the closing of voltage-gated Na+ channels
C. the closing of voltage-gated K+ channels
D. the opening of voltage-gated K+ channels

Hyperpolarization results from

A. slow closing of voltage-gated Na+ channels
B. fast closing of voltage-gated K+ channels
C. slow closing of voltage-gated K+ channels

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

A. 70 mV
B. 30 mV
C. 100 mV

What type of conduction takes place in unmyelinated axons?

A. Saltatory conduction
B. Continuous conduction
C. Synaptic transmission
D. Electrical conduction

An action potential is self-regenerating because __________.

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

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

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

What is the function of the myelin sheath?

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

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

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

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

A. Myelinated axons with the largest diameter.
B. Unmyelinated axons with the largest diameter.
C. Unmyelinated axons of the shortest length.
D. Myelinated axons with the smallest diameters.

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

A. K+; Cl–
B. Na+; Cl–
C. K+; Na+
D. Na+; K+

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

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

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

A. –90 mV
B. +30 mV
C. –70 mV

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

A. Both Na+ and K+ are pumped out of the cell.
B. K+ is pumped out of the cell and Na+ is pumped into the cell.
C. Both Na+ and K+ are pumped into the cell.
D. Na+ is pumped out of the cell and K+ is pumped into the cell.

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

A. K+ and Cl–
B. K+ and A– (negatively charged proteins) C. Na+ and A– (negatively charged proteins)
D. Na+ and Cl–

Local anesthetics block voltage-gated Na+ channels, but they do not block mechanically gated ion channels. Sensory receptors for touch (and pressure) respond to physical deformation of the receptors, resulting in the opening of specific mechanically gated ion channels. Why does injection of a local anesthetic into a finger still cause a loss of the sensation of touch from the finger?

A. The local anesthetic prevents Na+ from causing the initial depolarization of this sensory receptor.
B. The local anesthetic prevents any type of repolarization of this sensory receptor.
C. Touch stimulation of this sensory receptor requires that there be a simultaneous opening of voltage-gated Na+ channels and mechanically gated ion channels.
D. Touch stimulation of this sensory receptor will open the mechanically gated ion channels, but action potentials are still not initiated because propagation of an action potential requires the opening of voltage-gated Na+ channels.

Steps in transferring across chemical synapses

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

A. neurotransmitter.
B. synaptic cleft.
C. calcium channel.
D. vesicle.
E. synaptic terminal.

A molecule that carries information across a synaptic cleft is a ____________.

A. receiving neuron.
B. sending neuron.
C. synaptic cleft.
D. neurotransmitter.
E. synapse.

When calcium ions enter the synaptic terminal,

A. the inside of the receiving neuron becomes more negative.
B. neurotransmitter molecules are quickly removed from the synaptic cleft.
C. they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.
D. the inside of the receiving neuron becomes more positive.
E. they cause an action potential in the sending neuron.

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

A. vesicles in the synaptic terminal fuse to the plasma membrane of the sending neuron.
B. ion channels in the plasma membrane of the sending neuron open.
C. ion channels in the plasma membrane of the receiving neuron open.
D. the receiving neuron becomes more negative inside.
E. the receiving neuron becomes more positive inside.

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

A. the sending neuron becomes more positive inside.
B. the sending neuron becomes more negative inside.
C. the receiving neuron immediately generates an action potential.
D. the receiving neuron is less likely to generate an action potential.
E. the receiving neuron is more likely to generate an action potential.

Which of the following is true regarding a response to an excitatory event which might occur soon after the initial stimulus indicated in the graph?



A. An excitatory event may result in an action potential, but this will be less likely if the excitatory stimulus occurs during the response to the stimulus observed in the graph.
B. No action potential can be induced in the neuron by an excitatory event if it occurs during the response observed in the graph.
C. An excitatory event will be more likely to generate an action potential if it occurs during the response to the stimulus observed in the graph.

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

A. inhibitory postsynaptic potential
B. inhibitory action potential
C. action potential
D. excitatory postsynaptic potential

Which neurotransmitter(s) is/are the body's natural pain killer?

A. endorphins
B. substance P
C. acetylcholine
D. norepinephrine

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

A. diverging circuit
B. parallel after-discharge circuit
C. reverberating circuit
D. converging circuit

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

A. integration center
B. receptor
C. effector
D. sensory neuron

Which of the following allows us to consciously control our skeletal muscles?

A. the afferent division of the nervous system
B. the parasympathetic division of the autonomic nervous system
C. the somatic nervous system
D. the sympathetic division of the autonomic nervous system

The nervous system's functions

Which of the neuroglial cell types shown control the flow of cerebrospinal fluid within the CNS?



A
B
C
D

Which of the neuroglial cell types shown form myelin sheaths within the CNS?



A
B
C
F

Which of the neuroglial cell types shown are found in the PNS?



A
B
C
D
E

What structural classification describes the neuron associated with the neuroglia shown by E and F?



A. multipolar
B. unipolar
C. nonpolar
D. bipolar

Which lettered region in the figure is referred to as the soma?



A
B
C
D
E

What structural classification describes this neuron?



A. unipolar
B. multipolar
C. bipolar
D. nonpolar

Which areas of this neuron would be classified as receptive regions?



A. D only
B. Both A and B
C. Both A and E
D. E only

Which area would contain an abundance of vesicles containing neurotransmitter?



A
B
C
D
E

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?

A. astrocytes
B. microglia
C. oligodendrocytes
D. ependymal cells

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

A. astrocytes
B. oligodendrocytes
C. Schwann cells
D. satellite cells

Which of the following are bundles of neurofilaments that are important in maintaining the shape and integrity of neurons?

A. chromatophilic substance
B. axolemma
C. perikaryon
D. neurofibrils

Which of the following is true of axons?

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

Which of the following is the conducting region of the neuron?

A. axon
B. soma
C. dendrites
D. terminal boutons

Which criterion is used to functionally classify neurons?

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

Which of the following is NOT a functional classification of neurons?

A. interneurons
B. efferent
C. multipolar
D. sensory

Which of the following is NOT true of association neurons?

A. Association neurons account for over 99% of the neurons in the body.
B. Most association neurons are confined within the peripheral nervous system (PNS).
C. Association neurons are also known as interneurons.
D. Most association neurons are multipolar.

Neurons are also called nerve cells. True or False
True False

Unmyelinated fibers conduct impulses faster than myelinated fibers. True or False
True False

Which neuroglia are the most abundant and versatile of the glial cells?

A. ependymal cells
B. astrocytes
C. oligodendrocytes
D. Schwann cells

Which part of the neuron is responsible for generating a nerve impulse?

A. chromatophilic substance
B. soma
C. dendrite
D. axon

Which of the following types of neurons carry impulses away from the central nervous system (CNS)?

A. association
B. sensory
C. afferent
D. motor

Where do most action potentials originate?

A. Cell body
B. Nodes of Ranvier
C. Axon terminal
D. Initial segment

What opens first in response to a threshold stimulus?

A. Voltage-gated K+ channels
B. Voltage-gated Na+ channels
C. Ligand-gated Cl- channels
D. Ligand-gated cation channels

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

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

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

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

What event triggers the generation of an action potential?

A. The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.
B. The membrane potential must depolarize from the resting voltage of -70 mV to its peak value of +30 mV.
C. The membrane potential must return to its resting value of -70 mV from the hyperpolarized value of -80 mV.
D. The membrane potential must hyperpolarize from the resting voltage of -70 mV to the more negative value of -80 mV.

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

A. Voltage-gated Na+ channels change shape, and their inactivation gates close.
B. Voltage-gated K+ channels change shape, and their activation gates open.
C. Voltage-gated Ca2+ channels change shape, and their activation gates open.
D. Voltage-gated Na+ channels change shape, and their activation gates open.

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

A. Positive membrane potential
B. Threshold potential
C. Action potential
D. Resting membrane potential (RMP)

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

A. Voltage-gated channels
B. Ligand-gated channels
C. Leak channels
D. Sodium-potassium ATPases

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

A. The inside surface of the plasma membrane is much more negatively charged than the outside surface.
B. The inside surface of the plasma membrane is much more positively charged than the inside surface.
C. There is no electrical potential difference between the inside and the outside surfaces of the plasma membrane.
D. The outside surface of the plasma membrane is much more negatively charged than the inside surface.

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

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

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

A. The presence of concentration gradients and voltage-gated channels
B. The presence of concentration gradients and leak channels
C. The presence of concentration gradients and Na+-K+ pumps
D. The presence of a resting membrane potential and leak channels

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

A. Na+-K+ ATPase
B. H+-K+ ATPase
C. Na+ cotransporter
D. Na+ and K+ leaks

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



A. the voltage measured across the axon membrane at various points along an axon at a specific instance of time during an action potential
B. the speed of an action potential as it moves down the length of an axon
C. the voltage measured between the neuron cell body and the axonal terminals as an action potential is generated and decays
D. the voltage measured across the axon membrane at a specific point as an action potential travels past

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



A. the simultaneous opening of voltage-gated Na+ and K+ channels
B. opening of voltage-gated K+ channels
C. opening of chemically gated Na+ channels
D. opening of voltage gated Na+ channels
E. opening of chemically gated K+ channels

Which result of the stimulus applied is the likely cause of the response observed in the left graph?



A. opening of gated Cl- channels
B. opening of gated Ca2+ channels
C. opening of gated Na+ channels
D. opening of gated K+ channels

Arrange these parts in order, from left to right, of a successful direct depolarization path within one neuron.

axon, axon hillock, cell body, dendrite, presynaptic terminal

Which of the following best characterizes depolarization?

A. small consecutive steps of K+ entering the cytoplasm
B. mass movement of Na+ into the axon cytoplasm from the cell body to the terminal
C. small consecutive steps of Na+ exit from cytoplasm into extracellular fluid
D. small consecutive steps of Na+ penetration into the axon along its length

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

A. axonal Ca+2 is increased because endoplasmic reticulum voltage-gated calcium channels open and Ca+2 enters the cytoplasm.
B. voltage-gated membrane channels open, and multiple types of ions enter the cytoplasm, increasing the intracellular positive charge
C. voltage-gated membrane channels open, and Ca+2 enters the cytoplasm, increasing intracellular calcium
D. voltage-gated channels open, and K+ exits to the extracellular fluid, decreasing intracellular K+.

Which statement best describes exocytosis?

A. Membrane organelles fuse together and mix neurotransmitter.
B. Sodium from the action potential fuses with the membrane vesicle and releases the neurotransmitter in the cytoplasm, which can then diffuse out to the extracellular fluid.
C. Membrane organelles fuse with the membrane and release contents out of the cell.
D. Membrane organelles fuse with the membrane and release contents inside the cell

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

A. An increased viscosity of the fluid between neurons.
B. An increase in the amount of neurotransmitter exocytized by the presynaptic axon.
C. An increase in number of postsynaptic receptors.
D. An increase in the distance between the neurons.

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

The Neurotransmitter:
A. was degraded by enzymes before arriving at the postsynaptic membrane.
B. bound at postsynaptic receptors to open postsynaptic ion channels.
C. bound at postsynaptic receptors to initiate an action potential.
D. was reabsorbed by the presynaptic membrane before it diffused away.

Sequence at the chemical synapse

Which best represents synaptic transmission?

A. presynaptic axon to synapse to dendrite or postsynaptic cell body
B. presynaptic axon to presynaptic cell body to dendrite
C. presynaptic cell body to dendrite to synapse
D. presynaptic axon to synapse to postsynaptic axon

Predict the possible effect of a drug that totally blocks the neurotransmitter receptor on the postsynaptic membrane.

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

A. Local graded potentials and action potential transmission is blocked and there is no response by the postsynaptic cell, the muscle.
B. Transmission is slowed and there is a slower response.
C. There is no effect.
D. Transmission of the action potential will be enhanced and there is a faster contraction response by the muscle.

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

A. a neuron
B. a Schwann cell
C. a secretory cell
D. a muscle cell

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

A. chemically gated channels
B. Vesicles filled with neurotransmitter
C. axon terminal
D. calcium channels

What is the role of calcium in synaptic activity?

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

What is the role of neurotransmitter at a chemical synapse?

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

Neurotransmitter is released from presynaptic neurons through what mechanism?

A. endocytosis
B. pinocytosis
C. exocytosis
D. phagocytosis

What type of channel on the postsynaptic membrane binds neurotransmitter?

A. a leakage channel
B. a voltage-gated channel
C. a chemically gated channel
D. a mechanically gated channel

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

A. exocytosis and degradation
B. excitation and degradation
C. reuptake and degradation
D. reuptake and inhibition

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

A. (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
B. (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. (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
D. (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

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

A. postsynaptic neuron
B. synaptic cleft
C. presynaptic neuron

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

A. chemically gated Ca2+ channels
B. voltage-gated Na+ channels
C. voltage-gated K+ channels
D. voltage-gated Ca2+ channels

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

A. chemically gated; presynaptic
B. voltage-gated; presynaptic
C. chemically gated; postsynaptic
D. voltage-gated; postsynaptic

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

A. either depolarize or hyperpolarize
B. hyperpolarize
C. depolarize

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

A. acetylcholine
B. glutamate