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Chapter 8 Neurons: Cellular and Network Properties
1) The portions of a neuron that extend off of the roughly spherical cell body are
usually collectively called
A) protrusions.
2. B) processes.
3. C) prostheses.
4. D) projections.
Answer: B
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
2) Detailed understanding of the cellular basis of signaling in the nervous system
has led to good understanding of consciousness, intelligence, and emotion.
A) True
B) False
Answer: B
Section: Organization of the Nervous System Learning Outcome: 8.1
Bloom’s Taxonomy: Knowledge
3) Neurotransmitter is stored and released from
A) axon terminals only.
B) axon varicosities only.
C) dendritic spines only.
D) cell bodies only.
E) axon terminals and axon varicosities.
Answer: E
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
4) Information coming into the central nervous system is transmitted along
________ neurons.
A) afferent
B) sensory
C) efferent
D) afferent and sensory
E) sensory and efferent
Answer: D
Section: Organization of the Nervous System
Learning Outcome: 8.1
Bloom’s Taxonomy: Knowledge
5) The afferent and efferent axons together form the
A) central nervous system.
B) autonomic division system.
C) somatic motor division of the nervous system.
D) peripheral nervous system.
E) visceral nervous system.
Answer: D
Section: Organization of the Nervous System
Learning Outcome: 8.1
Bloom’s Taxonomy: Knowledge
6) The brain and spinal cord together compose the
A) central nervous system.
B) autonomic division system.
C) somatic motor division of the nervous system.
D) peripheral nervous system.
E) visceral nervous system.
Answer: A
Section: Organization of the Nervous System
Learning Outcome: 8.1
Bloom’s Taxonomy: Knowledge
7) Exocrine glands, smooth muscles, and cardiac muscles are controlled by the
A) central nervous system.
B) autonomic nervous system.
C) somatic motor division.
D) peripheral nervous system.
E) enteric nervous system.
Answer: B
Section: Organization of the Nervous System
Learning Outcome: 8.1 Bloom’s Taxonomy: Knowledge
8) Autonomic motor neurons are subdivided into the
A) visceral and somatic divisions.
B) sympathetic and parasympathetic divisions.
C) central and peripheral divisions.
D) visceral and enteric divisions.
E) somatic and enteric divisions.
Answer: B
Section: Organization of the Nervous System
Learning Outcome: 8.1
Bloom’s Taxonomy: Knowledge
9) The enteric nervous system is a network of neurons that function in controlling
A) reproduction.
B) digestion.
C) excretion, particularly urination.
D) the skeletal system.
E) the endocrine system.
Answer: B
Section: Organization of the Nervous System
Learning Outcome: 8.1
Bloom’s Taxonomy: Knowledge
10) In general, the nervous system is composed of which two types of cells?
1. motor
2. neurons
3. sensory
4. glial
5. associative
6. A) 1 and 2
7. B) 1 and 3
8. C) 2 and 4
9. D) 3 and 4
10. E) 3 and 5
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.1
Bloom’s Taxonomy: Knowledge
11) The cell body of neurons is generally
1. A) 90% of the cell volume.
2. B) 50% of the cell volume.
3. C) 10% of the cell volume.
4. D) found in the same position on every neuron.
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
12) Interneurons are found
1. A) only in the brain.
2. B) only in the spinal cord.
3. C) only in the CNS.
4. D) throughout the nervous system.
5. E) only in spinal nerves.
Answer: C
Section: Cells of the Nervous System Learning Outcome: 8.1
Bloom’s Taxonomy: Knowledge
13) The multiple thin, branched structures on a neuron whose main function is to
receive
incoming signals are the
1. A) cell bodies.
2. B) axons.
3. C) dendrites.
4. D) somata.
5. E) None of the answers are correct.
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.3
Bloom’s Taxonomy: Knowledge
14) The collection of axons that carries information between the central nervous
system and the
peripheral effectors is called the
1. A) axon hillock.
2. B) varicosity.
3. C) axon.
4. D) dendrite.
5. E) nerve.
Answer: E
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
15) The region where the axon terminal meets its target cell is called the
1. A) collateral.
2. B) hillock. 3. C) synapse.
4. D) nerve.
5. E) dendrites.
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.3
Bloom’s Taxonomy: Knowledge
16) The axon is connected to the cell body by the
1. A) myelin sheath.
2. B) axon terminal.
3. C) collaterals.
4. D) axon hillock.
5. E) synapse.
Answer: D
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
17) Branches that sometimes occur along the length of an axon are called
1. A) dendrites.
2. B) axon terminals.
3. C) collaterals.
4. D) axon hillocks.
5. E) synapses.
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.2 Bloom’s Taxonomy: Knowledge
18) Neurotransmitters are released from the
1. A) dendrites.
2. B) axon terminals.
3. C) collaterals.
4. D) axon hillock.
5. E) synapse.
Answer: B
Section: Cells of the Nervous System
Learning Outcome: 8.3
Bloom’s Taxonomy: Knowledge
19) The term axonal transport refers to
1. A) the release of neurotransmitter molecules from the axon.
2. B) the transport of microtubules to the axon for structural support.
3. C) vesicle transport of proteins and organelles down the axon.
4. D) the movement of the axon terminal to synapse with a new postsynaptic cell.
5. E) None of the answers are correct.
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
20) Anterograde and retrograde axonal transport are forms of ________ transport.
1. A) fast
2. B) slow
3. C) Neither of these. Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
21) Clusters of nerve cell bodies in the peripheral nervous system are called
1. A) microglia.
2. B) neuroglia.
3. C) glia.
4. D) ganglia.
5. E) nodes.
Answer: D
Section: Organization of the Nervous System
Learning Outcome: 8.1
Bloom’s Taxonomy: Knowledge
22) Glial cells
1. A) only provide structural and metabolic support.
2. B) only guide neurons during growth and repair.
3. C) only help maintain homeostasis of the brain’s extracellular fluid.
4. D) provide structural and metabolic support and help maintain homeostasis of
the brain’s extracellular fluid.
5. E) All of the answers are correct.
Answer: E
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
23) Glial cells communicate primarily using
1. A) electrical signals only.
2. B) chemical signals only.
3. C) neurotransmitters only.
4. D) neuromodulators only.
5. E) electrical signals and chemical signals.
Answer: B
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
24) Myelin is formed by
1. A) axons only.
2. B) Schwann cells only.
3. C) oligodendrocytes only.
4. D) Schwann cells and oligodendrocytes.
Answer: D
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
25) These glial cells act as scavengers.
1. A) Schwann cells
2. B) astrocytes
3. C) microglia
4. D) oligodendrocytes
5. E) ependymal cells
Answer: C Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
26) These glial cells may contribute to Lou Gehrig’s disease.
1. A) Schwann cells
2. B) astrocytes
3. C) microglia
4. D) oligodendrocytes
5. E) ependymal cells
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
27) The Nernst equation predicts
1. A) intracellular ion concentrations.
2. B) extracellular ion concentrations.
3. C) the membrane potential resulting from all permeable ions.
4. D) the membrane potential resulting from permeability to a single ion.
5. E) the threshold membrane potential.
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Comprehension
28) Which is the correctly written Nernst equation?
1. A) 61/z × log [ion]out/ [ion]in
2. B) 61/z × log [ion]in/ [ion]out 3. C) log 61/z × [ion]in/ [ion]out
4. D) log 61/z × [ion]out/ [ion]in
Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Comprehension
29) What does the Goldman-Hodgkin-Katz equation take into account that the
Nernst equation does NOT?
1. A) the electrical charges of the ions
2. B) the permeabilities of the ions
3. C) the solubilities of the ions
4. D) the sizes of the ions
5. E) the temperature
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Knowledge
30) The resting membrane potential results from
1. A) uneven distribution of ions across the cell membrane only.
2. B) differences in membrane permeability to Na+and K+
3. C) activity of the sodium/potassium pump only.
4. D) uneven distribution of ions across the cell membrane and differences in
membrane permeability to Na+and K+.
5. E) None of the answers are correct.
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.5 Bloom’s Taxonomy: Knowledge
31) Which ion(s) is/are higher in concentration inside the cell compared to outside?
1. A) potassium
2. B) sodium
3. C) chloride
4. D) calcium
5. E) More than one of the answers is correct.
Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Knowledge
32) The channelopathy known as QT syndrome is a result of mutation in ________
channels.
1. A) sodium
2. B) potassium
3. C) calcium
4. D) chloride
5. E) sodium, potassium, or calcium Answer: E
Section: Electrical Signals in Neurons
Learning Outcome: 8.6
Bloom’s Taxonomy: Knowledge
33) Ion channel inactivation is
1. A) closing of the channel in response to decrease in the stimulus.
2. B) closing of the channel even when the stimulus continues. 3. C) any type of
channel closing.
4. D) None of the answers are correct. Answer:
B
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
34) The total amount of neurotransmitter released at the axon terminal is directly
related to
1. A) the amplitude of the action potential.
2. B) the length of the axon.
3. C) the total number of action potentials.
4. D) the amplitude of the graded potential.
Answer: C
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.11
Bloom’s Taxonomy: Comprehension
35) Which of the following is the most common location where action potentials
originate?
1. A) dendrites
2. B) cell body
3. C) axon hillock
4. D) synaptic cleft
5. E) synaptic bouton
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
36) The rising phase of the action potential is due to
1. A) Na+flow into the cell only.
2. B) Na+flow out of the cell only.
3. C) K+flow out of the cell only.
4. D) K+flow into the cell only.
5. E) Na+flow out of the cell and K+flow into the cell.
Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
37) The falling phase of the action potential is due primarily to
1. A) Na+flow in the cell only.
2. B) Na+flow out of the cell only.
3. C) K+flow out of the cell only.
4. D) K+flow into the cell only.
5. E) Na+flow out of the cell and K+flow into the cell.
Answer: C
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
38) The point during an action potential when the inside of the cell has become
more positive
than the outside is known as the
1. A) depolarization.
2. B) rising phase.
3. C) falling phase.
4. D) overshoot.
5. E) peak.
Answer: D Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
39) Choose all of the items that are incorrectly matched.
1. A) inactivation gate — closed at rest
2. B) activation gate — open at rest
3. C) inactivation gate — closed during repolarization
4. D) activation gate — opens during depolarization
5. E) All of the answers are incorrectly matched.
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
40) The absolute refractory period of an action potential
1. A) only ensures one-way travel down an axon.
2. B) only allows a neuron to ignore a second signal sent that closely follows the
first.
3. C) only prevents summation of action potentials.
4. D) ensures one-way travel down an axon and allows a neuron to ignore a
second signal sent that closely follows the first.
5. E) ensures one-way travel down an axon, allows a neuron to ignore a second
signal sent that closely follows the first, and prevents summation of action
potentials.
Answer: E
Section: Electrical Signals in Neurons
Learning Outcome: 8.9
Bloom’s Taxonomy: Comprehension
41) In order to signal a stronger stimulus, action potentials become
1. A) higher in amplitude only.
2. B) more frequent only.
3. C) longer-lasting only.
4. D) higher in amplitude and more frequent.
5. E) higher in amplitude and longer-lasting.
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
42) All of the following must occur before a second action potential can begin,
EXCEPT
1. A) the Na+and K+ions that moved in/out of the cell must move back to their
original compartments.
2. B) the Na+inactivation gate must open and the Na+activation gate must close.
3. C) the absolute refractory period must occur.
4. D) the Na+and K+ions that moved in/out of the cell must move back to their
original
compartments; the Na+ inactivation gate must open; and the Na+ activation gate
must close.
5. E) None of the answers are correct.
Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.9
Bloom’s Taxonomy: Comprehension
43) Voltage-regulated channels are located
1. A) within the cytosol only.
2. B) in the membranes of dendrites only.
3. C) in the membranes of axons only.
4. D) on the neuron cell body only.
5. E) in the membranes of dendrites, in the membranes of axons, and on the
neuron cell body. Answer: E
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
44) The sodium-potassium exchange pump
1. A) must re-establish ion concentrations after each action potential.
2. B) transports sodium ions into the cell during depolarization.
3. C) transports potassium ions out of the cell during repolarization.
4. D) moves sodium and potassium in the direction of their chemical gradients.
5. E) requires ATP to function.
Answer: E
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
45) The all-or-none principle states that
1. A) all stimuli will produce identical action potentials.
2. B) all stimuli great enough to bring the membrane to threshold will produce
action potentials of identical magnitude.
3. C) the greater the magnitude of the stimuli, the greater the intensity of the
action potential.
4. D) only sensory stimuli can activate action potentials.
5. E) only motor stimuli can activate action potentials.
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge 46) When voltage-gated Na+ channels of a
resting neuron open,
1. A) Na+enters the neuron.
2. B) Na+leaves the neuron.
3. C) the neuron depolarizes.
4. D) Na+enters the neuron and the neuron depolarizes.
5. E) Na+leaves the neuron and the neuron depolarizes.
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
47) When voltage-gated K+ channels of a resting neuron open,
1. A) K+enters the neuron.
2. B) K+leaves the neuron.
3. C) the neuron depolarizes.
4. D) K+enters the neuron and the neuron depolarizes.
5. E) K+leaves the neuron and the neuron depolarizes.
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
48) In the membrane of a resting nerve cell, when chemically gated Cl- channels
open,
1. A) Cl- ions enter the cell.
2. B) Cl- ions leave the cell.
3. C) the cell becomes depolarized.
4. D) Cl- ions enter the cell and the cell becomes depolarized.
5. E) Cl- ions leave the cell and the cell becomes depolarized.
Answer: A Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
49) Ion concentrations are first significantly affected after ________ action
potential(s).
1. A) one
2. B) a few dozen
3. C) a few hundred
4. D) a few thousand
5. E) a few million
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
50) Action potentials are primarily associated with the membranes of
1. A) dendrites only.
2. B) cell bodies only.
3. C) axons only.
4. D) dendrites and axons.
5. E) cell bodies and axons.
Answer: C
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
51) Which of the following will best increase the conduction rate of action
potentials?
1. A) Increase the diameter of the axon, decrease the resistance of the axon
membrane to ion
leakage. 2. B) Increase the diameter of the axon, increase the resistance of the
axon membrane to ion
leakage.
3. C) Decrease the diameter of the axon, decrease the resistance of the
axon membrane to ion leakage.
4. D) Decrease the diameter of the axon, increase the resistance of the
axon membrane to ion leakage.
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Comprehension
52) Which of the following does NOT influence the time necessary for a nerve
impulse to be conveyed by a particular neuron?
1. A) length of the axon
2. B) presence or absence of a myelin sheath
3. C) diameter of the axon
4. D) presence or absence of nodes of Ranvier
5. E) whether axon is sensory or motor
Answer: E
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Comprehension
53) Graded potentials may
1. A) initiate an action potential.
2. B) depolarize the membrane to the threshold voltage.
3. C) hyperpolarize the membrane.
4. D) be called EPSPs or IPSPs.
5. E) All of the statements are true.
Answer: E Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
54) Some neurotoxins work essentially the same way as some local anesthetics,
which is to
1. A) inactivate the enzyme that destroys the neurotransmitter only.
2. B) bind to Na+channels and inactivate them only.
3. C) prevent depolarization by blocking Na+entry into the cell only.
4. D) inactivate the enzyme that destroys the neurotransmitter and bind to
Na+channels and inactivate them.
5. E) bind to Na+channels and inactivate them and prevent depolarization by
blocking
Na+entry into the cell.
Answer: E
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
55) The major determinant of the resting potential of all cells is
1. A) Ca2+concentration in the blood and interstitial fluid.
2. B) Na+concentration in the blood and interstitial fluid.
3. C) K+gradient between the blood and interstitial fluid.
4. D) K+concentration inside cells.
5. E) Na+concentration inside cells.
Answer: C
Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Knowledge
56) The term hyperkalemia specifically indicates too much potassium in which
fluid compartment?
1. A) blood
2. B) intracellular
3. C) interstitial
4. D) extracellular
5. E) All of the answers are correct.
Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Knowledge
57) A chemical synapse ALWAYS includes which of the following?
1. axon terminal
2. presynaptic cell
3. synaptic cleft
4. postsynaptic cell
5. dendrite
6. A) 1, 2, 3, 4, 5
7. B) 1, 2, 3, 4
8. C) 2, 3, 4
9. D) 2, 3, 4, 5
10. E) 1, 3, 4
Answer: B
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.11
Bloom’s Taxonomy: Knowledge
58) Which type of synapse is most prevalent in the nervous system?
1. A) chemical
2. B) electrical
3. C) mechanical
4. D) processing 5. E) radiative
Answer: A
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.11
Bloom’s Taxonomy: Knowledge
59) The ion necessary to initiate the release of acetylcholine into the synaptic cleft
is
1. A) sodium.
2. B) potassium.
3. C) calcium.
4. D) chloride.
5. E) zinc.
Answer: C
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.12
Bloom’s Taxonomy: Knowledge
60) To increase the amount of neurotransmitter released onto a postsynaptic cell,
the presynaptic cell would have to
1. A) send action potentials with higher voltage (higher amplitude).
2. B) send action potentials with longer durations.
3. C) send action potentials with higher frequency.
4. D) do nothing; no change is possible since the all-or-none law is in effect.
Answer: C
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13 Bloom’s Taxonomy: Comprehension
61) Which is/are the most common inhibitory neurotransmitter(s) of the CNS?
1. A) GABA only
2. B) glycine only
3. C) glutamate only
4. D) GABA and glycine
5. E) All of the answers are correct.
Answer: D
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.12
Bloom’s Taxonomy: Knowledge
62) The inhibitory neurotransmitters of the CNS, GABA and glycine, act by
opening ________ channels.
1. A) only Na+
2. B) only Cl-
3. C) only K+
4. D) only Ca2+
5. E) Na+and K+
Answer: B
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.12
Bloom’s Taxonomy: Knowledge
63) Excitatory neurotransmitters of the CNS usually act by opening ________
channels.
1. A) Na+
2. B) K+
3. C) Cl- 4. D) H+
5. E) Ca2+ Answer:
A
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.12
Bloom’s Taxonomy: Knowledge
64) Which of the following is NOT a known drug effect on synaptic function?
1. A) interfere with neurotransmitter synthesis
2. B) alter the rate of neurotransmitter release
3. C) prevent neurotransmitter inactivation
4. D) prevent neurotransmitter binding to receptors
5. E) change the type of neurotransmitter found in the synaptic vesicle
Answer: E
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Comprehension
65) The site of information integration in the nervous system is the
1. A) chemical synapse. 2.
B) electrical synapse.
3. C) trigger zone.
4. D) dendritic membrane.
5. E) axon terminal.
Answer: C
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Comprehension 66) Once the stimulus alters the receptor on
the cell’s membrane, what happens next?
1. A) Ion channels open, allowing ions to enter or exit.
2. B) The membrane permeability is altered.
3. C) A second messenger is activated on the inside of the cell.
4. D) Any of these actions could happen next.
Answer: D
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Comprehension
67) Once the action potential reaches the axon terminal, what happens next?
1. A) exocytosis of a neurocrine
2. B) release of the neurotransmitter into the synaptic cleft
3. C) release of a neurohormone into the blood
4. D) Any of the above could happen next.
Answer: D
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Comprehension
68) Calcium is important in the synapse because it
1. A) is necessary for acetylcholine synthesis.
2. B) signals the exocytosis of the neurotransmitter.
3. C) binds to receptors on the postsynaptic cell, opening ion channels, and
triggering graded potentials.
4. D) leaves the axon terminal, hyperpolarizing the cell.
Answer: B Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Knowledge
69) In response to binding a neurotransmitter, a postsynaptic cell can
1. A) only open chemically gated ion channels, causing graded potentials known
as fast synaptic
potentials.
2. B) only close ion channels via G proteins and second messenger systems,
producing slow responses.
3. C) only regulate protein synthesis and affect the metabolic activities of the
postsynaptic cell.
4. D) open chemically gated ion channels, causing graded potentials known as fast
synaptic
potentials and regulate protein synthesis and affect the metabolic activities of the
postsynaptic cell.
5. E) open chemically gated ion channels, causing graded potentials known as fast
synaptic
potentials, close ion channels via G proteins and second messenger systems,
producing
slow responses, and regulate protein synthesis and affect the metabolic activities of
the postsynaptic cell.
Answer: E
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Comprehension
70) The neurotransmitter thought to be involved in learning and memory is
1. A) norepinephrine.
2. B) glutamate.
3. C) acetylcholine.
4. D) GABA. 5. E) glycine.
Answer: B
Section: Integration of Neural Information Transfer Learning Outcome: 8.14
Bloom’s Taxonomy: Knowledge
71) In order for a synapse to be an effective means of cellular communication,
slow removal or inactivation of neurotransmitter molecules from the synapse
is important.
1. A) True
2. B) False
Answer: B
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Knowledge
72) Identify the FALSE statement.
1. A) EPSPs that reach threshold can initiate an action potential.
2. B) The trigger zone is the integrating center of the neuron.
3. C) IPSPs depolarize the membrane.
4. D) All of the statements are true.
Answer: C
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14
Bloom’s Taxonomy: Comprehension
73) An excitatory postsynaptic potential (EPSP)
1. A) depolarizes a neuron, decreasing the likelihood of an action potential.
2. B) hyperpolarizes a neuron, decreasing the likelihood of an action potential.
3. C) depolarizes a neuron, increasing the likelihood of an action potential.
4. D) hyperpolarizes a neuron, increasing the likelihood of an action potential.
Answer: C
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14
Bloom’s Taxonomy: Knowledge
74) Inhibitory postsynaptic potentials (IPSPs)
1. A) result in local depolarizations.
2. B) result in local hyperpolarizations.
3. C) increase membrane permeability to sodium ions.
4. D) prevent the escape of potassium ions.
5. E) prevent the escape of calcium ions.
Answer: B
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14
Bloom’s Taxonomy: Knowledge
75) When two or more graded potentials arrive at the trigger zone, which of the
following could happen?
1. A) An excitatory and inhibitory signal can cancel each other out.
2. B) Two excitatory stimuli may be additive, and summation could occur.
3. C) Two inhibitory stimuli may be additive, resulting in lower excitability.
4. D) An excitatory and inhibitory signal can cancel each other out and two
excitatory stimuli may be additive, and summation could occur.
5. E) An excitatory and inhibitory signal can cancel each other out; two excitatory
stimuli
may be additive, and summation could occur; and two inhibitory stimuli may be
additive, resulting in lower excitability.
Answer: E
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14 Bloom’s Taxonomy: Comprehension
76) Presynaptic facilitation makes a pathway
1. A) less likely to be in use, just through hyperpolarization of selected neurons.
2. B) more likely to be in use, just through depolarization of selected neurons.
3. C) capable of alteration, just through training and conditioning.
4. D) less likely to be in use, just through hyperpolarization of selected neurons
and capable of alteration, just through training and conditioning.
5. E) more likely to be in use, just through depolarization of selected neurons and
capable of alteration, just through training and conditioning.
Answer: E
Section: Integration of Neural Information Transfer
Learning Outcome: 8.16
Bloom’s Taxonomy: Comprehension
77) Spatial summation refers to
1. A) electrical signals reaching neurons from outer space.
2. B) multiple graded potentials arriving at one location simultaneously.
3. C) repeated graded potentials reaching the trigger zone one after the other.
4. D) suprathreshold potentials triggering action potentials that are extra large.
5. E) All of the answers are correct.
Answer: B
Section: Integration of Neural Information Transfer
Learning Outcome: 8.15
Bloom’s Taxonomy: Comprehension
78) If a hyperpolarizing graded potential and a depolarizing graded potential of
similar magnitudes arrive at the trigger zone at the same time, what is most likely to
occur?
1. A) An action potential is fired off more quickly than usual.
2. B) Nothing. They will cancel each other out.
3. C) The cell becomes hyperpolarized.
4. D) The cell becomes easier to excite.
5. E) The cell dies.
Answer: B
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14
Bloom’s Taxonomy: Comprehension
79) When multiple, possibly even conflicting signals reach a neuron, the neuron
evaluates the
signals and may respond or not. This property is called
1. A) temporal summation.
2. B) spatial summation.
3. C) postsynaptic integration.
4. D) graded potentials.
5. E) EPSPs.
Answer: C
Section: Integration of Neural Information Transfer
Learning Outcome: 8.15
Bloom’s Taxonomy: Comprehension
80) When a second EPSP arrives at a single synapse before the effects of the first
have disappeared, what occurs? 1. A) spatial summation
2. B) temporal summation
3. C) inhibition of the impulse
4. D) hyperpolarization
5. E) decrease in speed of impulse transmission
Answer: B
Section: Integration of Neural Information Transfer Learning Outcome: 8.15
Bloom’s Taxonomy: Comprehension
81) The pattern of synaptic connectivity where a large number of presynaptic
neurons provide
input to a single postsynaptic neuron, is known as
1. A) divergence.
2. B) convergence.
3. C) integration.
4. D) saltatory conduction.
5. E) potentiation.
Answer: B
Section: Integration of Neural Information Transfer
Learning Outcome: 8.16
Bloom’s Taxonomy: Comprehension
82) During childhood, growth and development of the brain PRIMARILY occurs
by increasing
1. A) neuron numbers only.
2. B) neuron size only.
3. C) number of dendrites and synapses only.
4. D) neuron numbers and neuron size.
5. E) neuron size and number of dendrites and synapses.
Answer: E
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Comprehension
83) The rearrangement of connections at synapses, which occurs throughout life, is
termed
1. A) elasticity.
2. B) intelligence.
3. C) plasticity. 4. D) senility.
5. E) synchronicity.
Answer: C
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14
Bloom’s Taxonomy: Knowledge
84) A damaged neuron has a better chance of survival and repair if the ________
is/are undamaged.
1. A) cell body
2. B) axon
3. C) dendrites
4. D) Schwann cells
5. E) axon and dendrites
Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Comprehension
85) Repair of damaged neurons can be assisted by certain neurotrophic factors
secreted by the 1. A) cell body only.
2. B) axon only.
3. C) dendrites only.
4. D) Schwann cells only.
5. E) axon and dendrites.
Answer: D
Section: Cells of the Nervous System Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
86) The tip of an embryonic nerve cell’s axon is called a
1. A) kissing cone.
2. B) stem tip.
3. C) growth cone.
4. D) growth tip.
5. E) None of the answers are correct.
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
Match the glial cell to the nervous system division in which it is found.
1. central nervous system
2. peripheral nervous system
87) Schwann cells
Answer: B
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
88) oligodendrocytes Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
89) microglia
Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
90) satellite cells
Answer: B
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
91) ependymal cells
Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
92) astrocytes
Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
Match the term with its description (answers may be used more than once).
1. ependymal cells
2. astrocytes
3. satellite cells
4. Schwann cells
5. oligodendrocytes
6. microglia
93) highly branched cells that transfer nutrients between blood vessels and
neurons
Answer: B
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
94) specialized immune cells that are confined to the CNS
Answer: F
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
95) cells that form supportive capsules around cell bodies
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
96) cells that create a selectively permeable epithelial layer to separate fluid
compartments of the
CNS
Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
97) cells in the CNS that form myelin
Answer: E
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
98) cells in the PNS that form myelin
Answer: D
Section: Cells of the Nervous System
Learning Outcome: 8.4 Bloom’s Taxonomy: Knowledge
99) cells that are a source of neural stem cells
Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
100) cells that myelinate several axons
Answer: E
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
101) cells that myelinate only one axon each; multiple cells per axon
Answer: D
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
Match the part of the neuron to its description (answers may be used more than
once).
1. dendrites
2. axon
3. cell body
102) may be covered with myelin
Answer: B
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
103) receive(s) most of the incoming synapses
Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
104) occupy(ies) the least amount of cell volume
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
105) make(s) proteins necessary for repair of damaged neuron
Answer: C Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
106) contribute(s) most to membrane surface area of cell
Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
107) supported by satellite cells
Answer: C
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
108) where most graded potentials originate
Answer: A
Section: Cells of the Nervous System
Learning Outcome: 8.3
Bloom’s Taxonomy: Knowledge
109) location of voltage-gated ion channels
Answer: B Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
Match the type of signal to its description (answers may be used more than once).
1. graded potential
2. action potential
3. both
110) may be hyperpolarizing
Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
111) originate(s) at the trigger zone
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
112) originate(s) on dendrites and cell bodies Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
113) can involve ion channels regulated by chemicals
Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
114) require(s) a minimum stimulus to occur
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
115) size increases if stimulus strength increases
Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
116) result(s) from influx of sodium Answer: C
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
117) The gaps between adjacent Schwann cells on an axon are called ________.
Answer: nodes of Ranvier
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
118) The potential difference across a membrane or other barrier is a measure of
the ________
across the barrier.
Answer: voltage
Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Knowledge
119) The sum of all of the electrical and chemical forces active across the
membrane is known as the ________.
Answer: driving force
Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Knowledge
120) The two types of electrical signals in neurons are ________.
Answer: graded potentials and action potentials
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
121) The minimum amount of stimulus required to depolarize an excitable
membrane and generate an action potential is known as the ________.
Answer: threshold
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
122) The ________ principle states that the properties of the action potential are
independent of the relative strength of the depolarizing stimulus.
Answer: all-or-none
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
123) The time during which an excitable membrane cannot respond to further
stimulation regardless of the stimulus strength is the ________.
Answer: absolute refractory period
Section: Electrical Signals in Neurons Learning Outcome: 8.9
Bloom’s Taxonomy: Knowledge
124) The period of time during which an excitable membrane can respond again,
but only if the stimulus is greater than the initial stimulus is the ________.
Answer: relative refractory period
Section: Electrical Signals in Neurons
Learning Outcome: 8.9
Bloom’s Taxonomy: Knowledge
125) At a(n) ________ synapse, a neurotransmitter is released to affect the
postsynaptic cell.
Answer: chemical
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.11
Bloom’s Taxonomy: Knowledge
126) In a(n) ________ synapse, there is a direct physical connection between cells.
Answer: electrical
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.11
Bloom’s Taxonomy: Knowledge
127) A ________ is a compound that influences a postsynaptic cell’s response to a
neurotransmitter.
Answer: neuromodulator Section: Cell-to-Cell Communication in the Nervous
System
Learning Outcome: 8.14
Bloom’s Taxonomy: Knowledge
128) The addition of stimuli arriving in rapid succession to produce an action
potential is called
________.
Answer: temporal summation
Section: Integration of Neural Information Transfer
Learning Outcome: 8.15
Bloom’s Taxonomy: Knowledge
129) The addition of several stimuli arriving from different locations on the same
cell to produce an action potential is called ________.
Answer: spatial summation
Section: Integration of Neural Information Transfer
Learning Outcome: 8.15
Bloom’s Taxonomy: Knowledge
130) Name the two factors that influence the membrane potential.
Answer:
1. the concentration gradients of ions across the membrane
2. the membrane permeability to those ions
Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Knowledge Indicate true or false. If FALSE, substitute a
word or phrase for the boldfaced word(s) that will make the statement TRUE.
131) Schwann cells are the primary type of glial cell associated with the central
nervous system.
Answer: False, peripheral nervous system
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
132) The gaps between Schwann cells are called synapses.
Answer: False, nodes of Ranvier
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
133) An influx of Na+ ions depolarizes the membrane of an axon.
Answer: True
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
134) The absolute refractory period is important in unidirectional propagation of
action
potentials.
Answer: True Section: Electrical Signals in Neurons
Learning Outcome: 8.9
Bloom’s Taxonomy: Knowledge
135) If the graded potential increases in amplitude, then the frequency of the action
potentials fired also increases.
Answer: True
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
136) In spatial summation the same stimulus is repeated until a threshold level of
depolarization is reached.
Answer: False, temporal summation
Section: Integration of Neural Information Transfer
Learning Outcome: 8.15
Bloom’s Taxonomy: Knowledge
137) Microvilli are present on cells that, because of their function, benefit from an
increased
membrane surface area. Which structure(s) on a neuron provide a comparable
benefit?
1. A) cell body
2. B) dendrites
3. C) axon
4. D) varicosities
5. E) collaterals
Answer: B Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Application
138) A home satellite dish receives signals from a satellite, allowing your
television to display
TV shows. Which part of a neuron is analogous to the satellite dish?
1. A) cell body
2. B) dendrites
3. C) axon
4. D) varicosities
5. E) collaterals
Answer: B
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Application
139) These CNS glial cells may be a source of treatment for neural degenerative
disorders.
1. A) Schwann cells
2. B) astrocytes
3. C) microglia
4. D) oligodendrocytes
5. E) ependymal cells
Answer: E
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
140) In terms of embryonic origin, neurons are most closely related to ________
cells.
1. A) skeletal muscle 2. B) cardiac muscle
3. C) connective tissue
4. D) epithelial
Answer: D
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Comprehension
141) If the resting axon’s membrane becomes more permeable to potassium ions,
1. A) the inside of the membrane will become more positively charged.
2. B) the membrane will depolarize more rapidly.
3. C) it will take a stimulus of larger magnitude to initiate an action potential.
4. D) the hyperpolarization at the end of the action potential will not occur.
Answer: C
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
142) If the sodium-potassium pumps in the cell membrane of a neuron fail to
function, over time
1. A) the extracellular concentration of potassium ion will increase.
2. B) the intracellular concentration of sodium ion will increase.
3. C) the membrane resting potential will become more positive than normal.
4. D) All of the answers are correct.
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.8 Bloom’s Taxonomy: Comprehension
143) How would the absolute refractory period be affected if voltage-gated sodium
channels remained inactivated?
1. A) It would be longer than normal.
2. B) It would be shorter than normal.
3. C) It would be the same whether the channels remained inactivated or not.
4. D) None of the answers are correct. Answer: A
Section: Electrical Signals in Neurons
Learning Outcome: 8.9
Bloom’s Taxonomy: Comprehension
144) Identify the FALSE statement.
1. A) Under normal conditions, all action potentials in a given cell are identical.
2. B) Between nodes of Ranvier, signal conduction is decremental.
3. C) The amplitude of the action potential depends on the amplitude of the graded
potential that precedes it.
4. D) The voltage-gated sodium and potassium channels begin to open during the
depolarization.
Answer: C
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Comprehension
145) When the neuron is at rest, which statement is true?
1. A) The activation gate is closed.
2. B) The inactivation gate is open.
3. C) No Na+crosses the membrane is the only observation. 4. D) The activation
gate is closed and the inactivation gate is open.
5. E) The activation gate is closed and no Na+crosses the membrane.
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
146) In the first phase of triggering an action potential in a neuron, Na+ ions flow
in and
1. A) only trigger a negative feedback loop.
2. B) only trigger a positive feedback loop.
3. C) only activate the sodium/potassium pump.
4. D) trigger a negative feedback loop and activate the sodium/potassium pump.
5. E) trigger a positive feedback loop and activate the sodium/potassium pump.
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
147) What stops the rising phase of the action potential?
1. A) The K+gate closes.
2. B) The Na+activation gate opens.
3. C) The Na+inactivation gate closes.
4. D) The Na+inactivation gate opens.
5. E) The sodium activation gate closes.
Answer: C
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
148) The inactivation gate
1. A) quickly opens and closes after depolarization.
2. B) is coupled to the movement of the activation gate, but is much slower.
3. C) depends on a change of +100 mV from rest to be signaled to close.
4. D) depends on a loss of Na+permeability to be triggered.
5. E) depends on a loss of K+permeability to be triggered.
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
149) During the relative refractory period, an initial threshold-level depolarization
is usually not sufficient to trigger an action potential. Why?
1. A) Only some Na+channels have returned to their resting position.
2. B) Only K+channels are still open, so Na+entry is offset by K+
3. C) Only a few K+channels have returned to their resting position.
4. D) The statement is incorrect; a threshold-level depolarization always triggers
an action potential.
5. E) Some Na+channels have returned to their resting position and K+channels
are still
open, so Na+ entry is offset by K+
Answer: E
Section: Electrical Signals in Neurons
Learning Outcome: 8.9
Bloom’s Taxonomy: Comprehension
150) The following are the main steps in the generation of an action potential:
1. sodium channels are inactivated
2. more voltage-regulated potassium channels open and potassium moves out of
the cell,
initiating repolarization
3. sodium channels regain their normal properties
4. a graded depolarization brings an area of an excitable membrane to threshold 5.
a temporary hyperpolarization occurs
6. sodium channel activation occurs
7. sodium ions enter the cell and further depolarization occurs
The proper sequence of these events is
1. A) 4, 6, 7, 3, 2, 5, 1.
2. B) 4, 6, 7, 1, 2, 5, 3.
3. C) 6, 7, 4, 1, 2, 3, 5.
4. D) 2, 4, 6, 7, 1, 3, 5.
5. E) 4, 2, 5, 6, 7, 3, 1.
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
151) When comparing action potentials to graded potentials, an/two important
distinguishing characteristic/s is/are
1. A) graded potentials can undergo summation.
2. B) action potentials can undergo summation.
3. C) that the rate of action potentials is limited by the refractory period.
4. D) graded potentials can undergo summation and the rate of action potentials is
limited by the refractory period.
5. E) action potentials can undergo summation and the rate of action potentials is
limited by the refractory period.
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
152) When more action potentials arrive at the axon terminal, how are
neurotransmitters affected?
1. A) More molecules are released into the synapse.
2. B) Different molecules are released into the synapse.
3. C) Fewer molecules are released into the synapse.
4. D) There is no effect—all signals are identical.
Answer: A
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Comprehension
153) When more action potentials arrive at the axon terminal, how is the
postsynaptic cell affected?
1. A) Neurotransmitter release increases, but does not change the graded
potentials that follow.
2. B) Neurotransmitter release does not change, thus the postsynaptic cell
behaves the same way it always behaves.
3. C) Neurotransmitter release increases, thereby increasing the frequency
or magnitude of graded potentials in the postsynaptic cell.
4. D) Neurotransmitter release does not change, but voltages applied to the
postsynaptic cell increase.
Answer: C
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Comprehension
154) If a stimulating electrode is placed in the middle of a resting axon and an
above-threshold
voltage is applied to the electrode action potentials
1. A) will not occur.
2. B) will start at that point and proceed only toward the axon terminal.
3. C) will start at that point and proceed only toward the cell body. 4. D) will start
at that point and travel in both directions in the axon.
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.9
Bloom’s Taxonomy: Application
155) Conduction occurs along an axon because
1. A) outflow of K+triggers the adjacent channels to open.
2. B) inflow of Na+triggers the adjacent channels to open.
3. C) once Na+enters the cell, the entire membrane depolarizes simultaneously.
4. D) axonal transport “walks” voltage changes along the membrane.
Answer: B
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Comprehension
156) Conduction speed is (or can be) enhanced by
1. A) myelin.
2. B) altering extracellular sodium concentration.
3. C) increasing the temperature.
4. D) altering extracellular potassium concentration.
5. E) myelin and increasing the temperature.
Answer: E
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Knowledge
157) When sodium channels open during an action potential, the opening is caused
by 1. A) binding of sodium ions.
2. B) binding of potassium ions.
3. C) presence of calcium.
4. D) presence of positive charge.
Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
158) The primary problem in hyperkalemia is
1. A) that neurons are harder to excite because their resting potential is
hyperpolarized.
2. B) that neurons are hyperexcitable because their resting potential is closer to
threshold.
3. C) that neurons respond too quickly to smaller graded potentials.
4. D) neurons are harder to excite because their resting potential is hyperpolarized
and neurons respond too quickly to smaller graded potentials.
5. E) neurons are hyperexcitable because their resting potential is closer to
threshold and neurons respond too quickly to smaller graded potentials.
Answer: E
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Comprehension
159) Graded potentials can
1. A) only act as signals over short distances.
2. B) only act as signals over long distances.
3. C) only cause or prevent an action potential.
4. D) act as signals over short distances and cause or prevent an action potential.
5. E) act as signals over long distances and cause or prevent an action potential.
Answer: D Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
160) The following are steps involved in transmission at the cholinergic synapse:
1. Chemically regulated ion channels on the postsynaptic membrane are activated.
2. Calcium ions enter the axon terminal.
3. An action potential depolarizes the axon terminal at the presynaptic membrane.
4. Acetylcholine is released from storage vesicles by exocytosis.
5. Acetylcholine binds to receptors on the postsynaptic membrane.
The correct sequence for these events is
3. A) 4, 2, 1, 5, 3.
4. B) 3, 2, 4, 5, 1.
5. C) 2, 4, 1, 3, 5.
6. D) 2, 5, 4, 1, 3.
7. E) 1, 2, 3, 4, 5.
Answer: B
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Comprehension
161) Arrange the following events in the proper sequence:
1. Efferent neuron reaches threshold and fires an action potential.
2. Afferent neuron reaches threshold and fires an action potential.
3. Effector organ responds by performing output.
4. Integrating center reaches decision about response.
5. Sensory organ detects change in the environment.
6. A) 2, 3, 5, 1, 4
7. B) 5, 2, 4, 1, 3
8. C) 5, 1, 4, 2, 3 9. D) 5, 3, 4, 2, 1
10. E) 3, 1, 4, 2, 5
Answer: B
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14
Bloom’s Taxonomy: Comprehension
162) How would blocking retrograde transport in an axon affect the activity of a
neuron?
1. A) The neuron would not be able to produce neurotransmitters.
2. B) The neuron would not be able to produce action potentials.
3. C) The cell body would not be able to export products to the axon terminals.
4. D) The cell body would not be able to respond to changes in the distal end of
the axon.
5. E) The neuron would be unable to depolarize when stimulated.
Answer: D
Section: Cells of the Nervous System
Learning Outcome: 8.3
Bloom’s Taxonomy: Comprehension
163) The basis of neural integration is
1. A) addition of postsynaptic potentials overlapping in time and space.
2. B) command signals from central pattern generators.
3. C) spontaneous activity in pacemaker neurons.
4. D) the area under the curve of postsynaptic potentials overlapping in time and
space.
Answer: A
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14
Bloom’s Taxonomy: Comprehension
164) Caffeine, nicotine, and alcohol all have effects on
1. A) action potential conduction.
2. B) long-term potentiation.
3. C) synaptic activity.
4. D) neurotransmitter degradation.
5. E) neurotransmitter reuptake.
Answer: C
Section: Integration of Neural Information Transfer
Learning Outcome: 8.17
Bloom’s Taxonomy: Knowledge
165) Tom’s father suffers a stroke that leaves him partially paralyzed on his right
side. What type
of glial cell would you expect to find in increased numbers in the damaged area of
the brain that is affected by the stroke? 1. A) astrocytes
2. B) Schwann cells
3. C) oligodendrocytes
4. D) microglia
Answer: D
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Application
166) Tetrodotoxin is a toxin that blocks voltage-gated sodium channels. What
effect does this
substance have on the function of neurons?
1. A) Neurons depolarize more rapidly.
2. B) Action potentials lack a repolarization phase.
3. C) The absolute refractory period is shorter than normal.
4. D) The neuron is not able to propagate action potentials.
5. E) The toxin does not interfere with neuron function because the
voltageregulated
sodium channels would still function. Answer: D
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Application
167) Inhibition of neural activity can result from
1. A) presynaptic events only.
2. B) postsynaptic events only.
3. C) presynaptic events and postsynaptic events.
Answer: C
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.16
Bloom’s Taxonomy: Knowledge
168) Presynaptic facilitation occurs when
1. A) extracellular concentration of sodium increases.
2. B) extracellular concentration of potassium increases.
3. C) calcium channels in the presynaptic membrane are inhibited.
4. D) calcium channels in the presynaptic membrane remain open longer.
5. E) temporal summation occurs.
Answer: D
Section: Integration of Neural Information Transfer
Learning Outcome: 8.16
Bloom’s Taxonomy: Knowledge
169) Learning and memory are thought to be due to a synaptic phenomenon known
as 1. A) inhibition.
2. B) excitation.
3. C) modulation.
4. D) facilitation.
5. E) long-term potentiation.
Answer: E
Section: Integration of Neural Information Transfer
Learning Outcome: 8.17
Bloom’s Taxonomy: Knowledge
170) Products from the cell body of a neuron are transported to the axon
terminals by ________.
Answer: (anterograde) axoplasmic transport
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
171) A change in the conditions in the axon terminal can cause a change in the
environment of the cell body as a result of ________. Answer: retrograde
transport
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
172) Graded potentials that increase the likelihood of an action potential bring
the
________
closer to threshold.
Answer: membrane potential Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
173) Graded potentials that arrive at postsynaptic neurons are called ________ if
they make that cell more likely to fire.
Answer: excitatory
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
174) Graded potentials that arrive at postsynaptic neurons are called ________ if
they make that cell less likely to fire.
Answer: inhibitory
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Knowledge
175) For ________ to occur, a second potential must arrive before a previous
one has been completed.
Answer: summation
Section: Integration of Neural Information Transfer
Learning Outcome: 8.15
Bloom’s Taxonomy: Knowledge 176) When two or more graded potentials arrive
at the trigger zone within a short period of time, their effects are additive and
________ occurs.
Answer: summation
Section: Integration of Neural Information Transfer
Learning Outcome: 8.15
Bloom’s Taxonomy: Knowledge
177) Receptors that work through second messenger systems are called ________
receptors.
Answer: metabotropic
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14
Bloom’s Taxonomy: Knowledge
178) Briefly explain the gross organization of the nervous system in either
paragraph form or
using a concept map. Be sure to discuss the central, peripheral, and enteric
nervous system and the divisions and branches discussed in the text.
Answer: Answers will vary. There are three divisions: the central nervous system
(CNS), the
peripheral nervous system (PNS), and the enteric nervous system. The CNS
consists of the brain
and spinal cord and acts as the integrating center for neural reflexes. The brain is
also where
thoughts and consciousness are formed. The PNS includes the afferent branch,
which monitors
the internal and external environment and sends signals to the CNS, and the
efferent branch,
which carries signals from the CNS to effector cells throughout the body. Within
the efferent
branch, there is the somatic motor division, which controls skeletal muscle, and the
autonomic
division. The autonomic division, or visceral nervous system, controls the smooth
and cardiac
muscles and exo- and endocrine glands. It is further divided into the sympathetic
and parasympathetic branches.
Section: Organization of the Nervous System
Learning Outcome: 8.1
Bloom’s Taxonomy: Comprehension
179) Draw a motor neuron, being sure to include and label the following parts:
axon(s),
dendrite(s), cell body, axon collateral(s), axon terminal(s), myelin sheath, and other
components as applicable.
Answer: See Figure 8.2 in the chapter
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Knowledge
180) Why are mitochondria necessary at axon terminals?
Answer: Energy is required in order to move synaptic vesicles to the cell
membrane.
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Comprehension
181) Why is it necessary for fast axonal transport to go both forward and
backward?
Answer: The organelles and cellular components transported to the axon terminal
must also be
returned to the cell body for recycling. Fast retrograde recycling may also be used
for nerve growth factor transport to the cell body.
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Comprehension
182) Compare and contrast action and graded potentials. Your answer should
include a definition
of each, types, characteristics, ionic basis, functions, and anything else necessary to
answer the
question. Answer: Action potentials are stereotyped changes in axon membrane
potential that function in
long-distance communication between neurons and their target cells. Graded
potentials are
variable membrane potential changes, usually in dendrites of multipolar neurons,
that function in
either short-distance communication or changing the probability of an action
potential.
Action potentials result from opening of voltage-regulated ion channels, which
occurs at or
above a threshold voltage. Graded potentials are not regenerative and result from
the opening of
ion channels in response to neurotransmitter or a specific stimulus such as sound
or odor, in the case of sensory receptors.
The rising phase results from influx of sodium, and the falling phase from efflux of
potassium.
Other characteristics include the after-hyperpolarization, all-or-none nature,
conduction without
decrement, independence of amplitude and duration from stimulus strength,
refractory period,
faster velocity in larger diameter or in myelinated axons. Graded potentials can be
depolarizing,
if the ion channel is a sodium channel, or hyperpolarizing in the case of potassium
or chloride
channels. Depolarizations increase the probability that threshold voltage will be
attained and an
action potential will result. Hyperpolarizations decrease the probability of a
resulting action
potential. Amplitude and duration are proportional to stimulus intensity, and
graded potentials are conducted with decrement.
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Comprehension
183) Compare and contrast fast and slow synaptic potentials, including detailed
mechanisms used and what kinds of cells they occur in.
Answer: Fast synaptic potentials begin quickly and last only a few milliseconds;
this category
includes EPSPs and IPSPs. Slow synaptic potentials take longer to begin and last
longer
commonly involve G-protein coupled receptors; this type of response is important
in growth, development, and long-term memory.
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14 Bloom’s Taxonomy: Comprehension
184) How does the function of dendritic spines in the CNS differ from dendrites in
the PNS?
Answer: Dendritic spines have polyribosomes to make their own proteins, send
signals to other
neurons, and are involved in learning, memory, and various pathologies. PNS
dendrites receive external information and transfer it within the neuron.
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Comprehension
185) Compare and contrast Schwann cells and oligodendrocytes.
Answer: Both insulate axons by creating myelin. Schwann cells, found in the PNS,
are
associated with a single axon. One axon may have many Schwann cells wrapped
around it leaving small gaps of unmyelinated areas called nodes of Ranvier.
Oligodendrocytes are found in the CNS and form myelin around portions of
several axons.
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Comprehension
186) Write out the Nernst and GHK equations, and explain the significance of
each.
Define equilibrium
potential.
Answer: This is discussed in the “Electrical Signals in Neurons” section of the
chapter. The
Nernst equation is used to calculate the equilibrium potential for individual ions,
while the GHK
equation calculates the predicted resting membrane potential of a cell. The
equilibrium potential
is the voltage at which there is no net movement of a particular ion across the
membrane,
because the force of the concentration gradient is exactly balanced by the force of
the electrical
gradient.
Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Knowledge
187) What is a channelopathy, and what are some examples?
Answer: See the first “Clinical Focus” box in the chapter.
Section: Electrical Signals in Neurons
Learning Outcome: 8.6
Bloom’s Taxonomy: Knowledge
188) What causes a graded potential to degrade?
Answer: Current leakage across the membrane and resistance of the cytoplasm are
two factors.
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Comprehension
189) Name two ways a cell changes its membrane permeability to ions. (Hint: One
way is relatively slow.) Answer:
1. opens or closes existing channels
2. inserts or removes membrane channels
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
190) If both Na+ and K+ channels are activated by depolarization, why do we see
more Na+ flux
during the rising phase of an action potential? Answer: Although both channels are
activated by depolarization, the Na+ channels open quickly
allowing rapid Na+ entry into the cell. The peak of Na+ permeability coincides
with the peak of the action potential, while the K+ channels open more slowly
and don’t reach their peak ion permeability until the falling phase of the action
potential.
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
191) What is the trigger zone? Where is the trigger zone found in efferent,
afferent, and interneurons? Do the terms trigger zone and axon hillock have the
same meaning? Explain.
Answer: The trigger zone is an area of the neuron that contains a high membrane
concentration
of voltage-gated Na+ channels and is near an area that lacks these. In order for
action potentials
to occur, graded potentials reaching the trigger zone must depolarize the membrane
to the
threshold voltage. In efferent and interneurons, the trigger zone is the axon hillock
(also called
the initial segment). In afferent neurons, the trigger zone is located where the
dendrites join the
axon (immediately adjacent to the receptor), rather than at the axon hillock. The
axon hillock is
an anatomical region, whereas the trigger zone is defined by its function rather than
its location.
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Knowledge
192) “A refractory period occurs following all types of potentials.” Is this
statement TRUE or
FALSE? What structures are actually refractory? Why or why not?
Answer: False. The refractory period occurs after action potentials and is a
distinguishing characteristic, and results from properties of the voltage-gated
sodium channels. Graded
potentials do not involve channels that have refractory periods. Two stimuli that
reach a dendrite
at nearly the same time will increase the graded potential produced, whereas if two
suprathreshold depolarizations reach the trigger zone at nearly the same time, the
first will cause an action potential and the second will be ignored, because of the
refractory period.
Section: Electrical Signals in Neurons
Learning Outcome: 8.9 Bloom’s Taxonomy: Comprehension
193) The text states “all action potentials are identical to one another.” There is
an exception, however, where an action potential can have a smaller than
normal amplitude. When does this occur and how?
Answer: During the relative refractory period, a smaller than normal action
potential can occur.
During this period potassium channels are still open causing repolarization. If a
wave of
depolarization occurs, Na+ can enter the cells through the newly reopened Na+
channels, but this depolarization is offset by the K+ efflux.
Section: Electrical Signals in Neurons
Learning Outcome: 8.9
Bloom’s Taxonomy: Comprehension
194) Explain the kiss-and-run model of synaptic vesicle exocytosis, and how it
differs from the classic model.
Answer: With the kiss-and-run model the synaptic vesicles fuse to the presynaptic
membrane at
a fusion complex. When the neurotransmitter is released through the fusion
complex into the
synaptic cleft the vesicles then pull away from the complex and re-enter the vesicle
pool in the
cytoplasm. With the classical model the vesicle becomes incorporated into or
becomes part of the cell membrane.
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Comprehension
195) Discuss the membrane permeabilities of major ions and how they contribute
to the overall resting membrane potential of neurons.
Answer: The average resting membrane potential is -70 mV. It is primarily
determined by the
concentration gradient of K+ and the membrane permeabilities of K+, Na+, and Cl.
The
equilibrium potential for K+ predicted by the Nernst equation is -90 mV. The
resting membrane potential is more permeable to K than Na. However,
because the cell’s resting potential is more
positive than -90mV there must be another contributing ion, and it is the Na+ leak
channels that
allow positive Na+ ions into the cell which cause the resting potential to be slightly
more
positive. Section: Electrical Signals in Neurons
Learning Outcome: 8.5
Bloom’s Taxonomy: Comprehension
196) If potassium channels in a neuron were blocked, would it be possible to
produce an action potential? If so, describe the probable appearance of these
components of a graph: threshold, rising phase, peak, falling phase, undershoot.
If not, explain.
Answer: Assuming sodium channels are functioning normally, there would still be
an action
potential. Threshold would be unaffected, because it is a property of sodium
channels. A peak
voltage will be reached when the sodium channels become inactivated; this voltage
may be
higher than normal since usually there is a partial canceling of the rising voltage as
potassium
exits. Without a potassium current, the falling phase would be much slower, being
dependent on
the sodium-potassium pump removing the sodium ions that came in. The
undershoot would be absent because it is a result of potassium current.
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
197) Explain why the voltage-gated Na+ channels can close while the cell is
depolarized even
though the depolarization was the initial stimulus for the channel opening. Include
a discussion on refractory periods and explain why action potentials travel in only
one direction.
Answer: The channels have two gates: activation and inactivation gates. (See Fig.
8.10.) At rest,
the activation gate is closed and the inactivation gate is open. Upon depolarization
both gates
move: the activation gate opens allowing Na+ to enter the cell and the inactivation
gate (with a delay of 0.5 msec) closes stopping the influx of Na+.
At this point during the action potential, the peak has been reached and
repolarization occurs due
to the K+ ions leaving the cell. During this time, even if another wave of
depolarization
occurred, the Na+ channels cannot be opened because the activation gate is already
open and the
inactivation gate is closed. This is the absolute refractory period, when another
action potential
absolutely cannot occur because the Na+ channels have not reset to their original
positions. The
relative refractory period occurs after some of the Na+ channels have reset, but a
higher than normal depolarizing graded potential is necessary to cause another
action potential.
Refractory periods also explain why action potentials cannot move backward.
(See Fig. 8.15.)
The part of the axon experiencing the action potential has open Na+ channels. An
increase in
Na+ inside the cell causes depolarization and perpetuates the action potential
toward the axon
terminal due to local current flow. The area of the axon toward the trigger zone,
where the action
potential (AP) occurred a moment earlier, is in the absolute refractory period and
will not experience another action potential even with a depolarization.
Section: Electrical Signals in Neurons
Learning Outcome: 8.8, 8.9
Bloom’s Taxonomy: Comprehension
198) Explain the two reasons why graded potentials lose strength as they
move through the cell.
Why don’t action potentials lose strength?
Answer: As a depolarization wave moves through the cell, some of the positive
charge is lost to
the extracellular fluid through leak channels. Additionally there is cytoplasmic
resistance. Action
potentials do not lose strength because they are regenerated in each patch of
membrane.
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Comprehension
199) Compare and contrast the EPSP, IPSP, and action potential as to ions
involved, all-or-none law application, specific cellular locations, and specific
cell types involved.
Answer: EPSPs and IPSPs are graded potentials in postsynaptic cells resulting
from the action
of neurotransmitters at synapses, which are usually on dendrites of multipolar
neurons, but could
also be on the synaptic region of any target cell. EPSPs increase the probability that
a
postsynaptic action potential will result, because they involve an influx of sodium,
which
depolarizes the membrane potential, bringing it closer to threshold. IPSPs decrease
the
probability that a postsynaptic action potential will result, because they involve
either an influx
of chloride or an efflux of potassium, either of which hyperpolarizes the membrane
potential, moving it farther from threshold.
Action potentials occur in axons of neurons, or in muscle cell membranes. They
may result from
PSPs or in the case of sensory neurons, specific stimuli such as sound or odor,
which cause a type of graded potential called a receptor potential. Action potentials
begin when graded
potentials depolarize the membrane potential to threshold. The rising phase of an
action potential
results from sodium influx, and the falling phase from potassium efflux. Action
potentials, but not graded potentials, are an all-or-none phenomenon.
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14
Bloom’s Taxonomy: Comprehension
200) Define temporal and spatial summation. Where does the summation occur?
Are these
processes mutually exclusive, or can they occur at the same time in a typical
multipolar neuron?
What key property of neurons do these forms of summation demonstrate?
Answer: See Figs. 8.24 and 8.25 in the chapter. Temporal summation is the
addition of graded
potentials that overlap in time; that is, a second potential arrives before the first one
from that
source has finished. Spatial summation occurs when there is simultaneous arrival
of graded
potentials originating from more than one synaptic input. Summation occurs at the
trigger zone.
Typically a multipolar neuron has many active synapses at a given time, with
multiple potentials being produced at each. Summation demonstrates
postsynaptic integration.
Section: Integration of Neural Information Transfer
Learning Outcome: 8.15
Bloom’s Taxonomy: Comprehension
201) Your study partner has concluded that a single action potential, once initiated,
spreads down
the length of an axon, non-decrementally; similarly, a single graded potential
spreads down the
length of a dendrite, but with decrement. Is she completely correct? Explain. How
can the mechanism of decremental and non-decremental conduction help her sort
this out? How is the
process different in myelinated vs. unmyelinated neurons? How may the dominoes
analogy help her to understand signal propagation?
Answer: While she is correct about graded potentials, she is incorrect about action
potentials. A
GP is initiated at a synapse, for example, and spreads in all directions but loses
strength as the
ions diffuse; no additional ions are crossing the membrane to boost this signal. An
AP is initiated
at a trigger zone, then a second, identical AP is triggered in the next patch of
membrane as more
ions enter the cell; thus, there was no decrement of the AP. Between membrane
patches, the
signal is decremental for the same reasons that GPs decrease with spread, but
sufficient to
stimulate the next AP. In myelinated axons, the subsequent APs are farther apart
than in unmyelinated axons. A row of dominoes, if spaced appropriately, can be
felled by pushing on
just the first one. That domino falls and does not spread to the end of the row, but it
causes its neighboring, identical domino to fall, and so on.
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Analysis
202) Polio is an uncommon disease in most developed countries, but prior to
widespread use of
the polio vaccine, it was very common. Polio is caused by a virus that infects
somatic motor
neurons and destroys them. From this information, would you expect a polio
victim to lose sensation, motor control, other organ function, and/or cognitive
function? Explain. While most victims of polio survive, some do not. What is the
most likely cause of death?
Answer: If only motor neurons are affected, the primary result should be paralysis
or inability to
control skeletal muscles. Because respiration involves skeletal muscles, some
victims die of suffocation.
Section: Organization of the Nervous System
Learning Outcome: 8.1
Bloom’s Taxonomy: Analysis
203) In a laboratory situation, a nerve can be stimulated by applying voltage from a
stimulator. If
a stimulus was applied in the middle of a nerve roughly halfway between the cell
bodies and the
axon terminals, would resulting action potentials travel only from the stimulus
point to the axon
terminal? Why or why not? How is this similar to or different from the basic
characteristics of an
action potential discussed in this chapter? What does this tell you about the nature
of the axon?
Answer: Action potentials would travel in both directions from the stimulus point,
simultaneously toward the cell bodies and toward the axon terminals. This is
because the axon
segments on each side of the stimulus point are presumably not refractory when the
stimulus is
delivered, thus there is nothing to prevent the action potentials from traveling in
both directions.
In normal transmission, the action potential begins where the axon starts, and
travels only away
from that point, not toward, because the membrane becomes refractory for a period
of time after
the action potential occurs. Thus, the axon is quite capable of transmitting action
potentials in
either direction, even though normally it is prevented from doing so. Section:
Electrical Signals in Neurons
Learning Outcome: 8.9
Bloom’s Taxonomy: Application
204) Dr. Zoydburger has discovered a toxin produced in the venom of a poisonous
marine
invertebrate. Tests on lab mammals indicate that this toxin prevents sodium
channel inactivation.
How would this affect the action potentials produced in the neurons of a poisoned
mammal?
Answer: Without sodium channel inactivation, the action potential would not
repolarize as
quickly, thus any function dependent upon the action potential would be prolonged,
including
neurotransmitter release and postsynaptic response. Also, the refractory period
would not exist, thus action potentials would travel back up the axon, and down
again, repeatedly.
Section: Electrical Signals in Neurons
Learning Outcome: 8.8, 8.9
Bloom’s Taxonomy: Application
205) Your study partner in your physiology class insists that axons conduct graded
potentials,
and that they play a vital role in production of the action potential. Do you agree or
disagree?
Defend your answer.
Answer: Your study partner is correct. This is easiest to explain in the context of
the myelinated
axon. Voltage-regulated ion channels, which produce the action potential, are
located only at
nodes of Ranvier. This means that the intervening regions do not generate action
potentials. After
an action potential is produced at one node, the ions diffuse from this node to the
next in a
decremental manner, but produce sufficient depolarization at the next node to
produce an action potential there.
Section: Electrical Signals in Neurons
Learning Outcome: 8.7
Bloom’s Taxonomy: Application
206) A compound action potential is recorded using electrodes on a nerve. How
does a nerve
differ from an axon? Amplitude and duration of a compound action potential vary
according to the stimulus intensity applied to the nerve. Given that there is no
such variation in the action potential of a single axon, how can you explain this?
Answer: A nerve consists of many axons. A regular action potential is produced
by a single
axon, whereas a compound action potential is recorded by equipment from a nerve
when
multiple axons are producing action potentials, and the voltages add together.
Increasing
stimulus intensity increases the number of axons contributing to the compound
action potential.
This is because different axons have different threshold voltages, so increasing the
voltage stimulates a larger number of axons.
Section: Electrical Signals in Neurons
Learning Outcome: 8.2, 8.8
Bloom’s Taxonomy: Analysis
207) Explain the processes that lead to the exocytosis of neurotransmitter from a
presynaptic
cell. Which components are recycled? Which ion is important in triggering
exocytosis?
Answer: Action potential arrives in synaptic terminal, and stimulates opening of
voltage-
regulated calcium channels. The resulting calcium influx triggers exocytosis of
synaptic vesicle
contents. The phospholipids of the vesicle membranes are recycled, either from
fusion of
vesicles then later formation of new vesicles from the same molecules; or from the
kiss-and-run
model, in which the vesicle phospholipids are not incorporated into the membrane
at all, but remain as vesicles that can be refilled with neurotransmitter.
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.13
Bloom’s Taxonomy: Comprehension
208) How do the following relate to nervous system development and/or healing?
Synaptic plasticity, neuroglia,
neurotrophic factors.
Answer: Synaptic plasticity is the changeability of synapses, necessary for
development and
continued learning in the nervous system. Neuroglia play an important role in
healing of
damaged neural tissue. Schwann cells in the PNS facilitate regrowth of severed
axons. CNS glia
seal off and scar a damaged region. Neurotrophic factors are important in
maintaining active synapses.
Section: Organization of the Nervous System
Learning Outcome: 8.1 Bloom’s Taxonomy: Application
209) The disease rabies is caused by a virus that attacks the central nervous system.
The virus is
normally introduced when an infected animal bites another, breaking the surface of
the skin and
allowing the entry of saliva containing the virus. Since the virus cannot move by
itself, how does it get to neurons in the central nervous system?
Answer: Circulation of the lymph may spread the virus throughout the body.
Retrograde axonal transport brings the viral particles to the nerve cell bodies
in the spinal cord.
Section: Cells of the Nervous System
Learning Outcome: 8.2
Bloom’s Taxonomy: Application
210) In multiple sclerosis, there is progressive and intermittent damage to the
myelin sheath of
central axons. One symptom is poor motor control of the affected area. Why does
destruction of the myelin sheath affect motor control?
Answer: Loss of myelin slows or stops impulse conduction, preventing descending
tracts from
regulating spinal motor neurons, and leading to loss of coordination and the ability
to correct for gravity, movement, and so on.
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Comprehension
211) Multiple sclerosis (MS) is one of the better known diseases resulting from
demyelination of
axons (in MS, only CNS axons are affected). Some of the earliest symptoms of the
disease are
difficulty in focusing the eyes, such as in reading, and difficulty in maintaining
balance, and
frequently not being able to make adjustments in posture to avoid falling. How do
these symptoms “fit” with what you know about nerve impulses, myelin sheaths,
and the location of gated ion channels in the membranes of axons?
Answer: Symptoms listed all involve loss of motor control. The CNS axons
involved in
initiating and controlling movement are generally myelinated, thus loss of
myelination slows or
eliminates conduction of action potentials in these cells. Early on, many signals
arrive normally at spinal motor neurons to produce movement, but enough signals
are missing to cause noticeable alterations in motor control.
In other words, loss of myelin slows or stops impulse conduction and leads to loss
of
coordination and the ability to correct for gravity, movement, and so on. Gated ion
channels should be intact at the nodes of Ranvier, but missing elsewhere along
the axon. Nodes are
generally far enough apart that without myelin, sufficient positive current from one
active node
does not arrive at the next node to bring it to threshold as quickly as normal or at
all, and impulse conduction slows or stops.
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Application
212) What factors determine the maximum frequency of action potentials
conducted by an axon?
Answer: Maximum frequency is mostly dependent upon the duration of the
absolute refractory
period, which determines the upper limit. The diameter of the axon, amount of
myelination
present, and the magnitude of the Na+ and K+ gradients across the axonal
membrane all affect action potential velocity may also play a secondary
role.
Section: Electrical Signals in Neurons
Learning Outcome: 8.4
Bloom’s Taxonomy: Knowledge
213) Compare and contrast the communication mechanisms between the nervous
and endocrine
systems. In other words, how do neurons and neurotransmitters signal to their
postsynaptic cells,
compared to the way endocrine glands and hormones communicate with their
target cells?
Answer: (Note to instructor: Students must have already completed the endocrine
chapter(s) in order to answer this.)
Neurotransmitters usually do not enter the cell, thus must combine with receptors
on the membrane, using mechanisms similar to the amino acid-derivative
hormones. Similarities
include opening channels in the postsynaptic cell membrane, leading to
depolarization of the
neuron. In endocrine target cells, the arrival of the stimulus begins a different
sequence of events, such as triggering an enzyme cascade, and second
messenger systems. Section: Cell-to-Cell Communication in the Nervous
System
Learning Outcome: 8.13
Bloom’s Taxonomy: Application
214) You and your lab partner have prepared a frog nerve for gathering data on
action potentials.
You connect an electronic stimulator to the nerve and ask your partner to gradually
increase the
voltage until you see an action potential. Your partner says that the voltage knob is
stuck, that is,
it will not increase the voltage. Is there another way to trigger action potentials
using this stimulator? If so, what do you tell your partner to do?
Answer: Your lab partner can increase the stimulus frequency instead. A higher
frequency of
stimuli can result in temporal summation of graded potentials such that the lower
voltages sum to threshold.
Section: Integration of Neural Information Transfer
Learning Outcome: 8.15
Bloom’s Taxonomy: Comprehension
215) A lab technician has inadvertently substituted lithium for sodium in a solution
of saline for
use by students in neurophysiology labs. If a frog nerve was bathed in this solution,
what would happen upon stimulation of the nerve?
Answer: Assuming the specificity of the voltage-regulated sodium and potassium
channels is
absolute, the axons will be unable to generate action potentials. The sodium
channels will open
and close, but there will be no ionic current through them. The students will still
see hyperpolarization, as the potassium efflux should be unaffected by lithium.
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Analysis
216) Explain the differences in axon regeneration in the CNS and PNS, and the
implications for
recovery from injury. What experiments might scientists try based on these
differences? Answer: Schwann cells, present in the PNS but not the CNS,
facilitate regrowth of severed
axons. This means that people do not recover as well from CNS injury compared to
PNS injury.
It is possible that there is something fundamentally different in CNS axons
compared to PNS
axons that accounts for this effect. To test for this, Schwann cells could be
transplanted into the
spinal cord or brain and CNS axons observed for regrowth. Such experiments have
been done,
and it is the case that CNS axons are capable of regrowth in the presence of
Schwann cells.
Identification of chemical or physical factors in the Schwann cells would advance
this field of research.
Section: Cells of the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Application
217) Create diagrams (of the cells) and graphs (of the potentials) to illustrate the
two different
situations described below in a multipolar neuron with a threshold voltage of 15
mV above
resting potential. In each, indicate decrement of graded potentials (by drawing the
same GP at different points as it spreads along the neuron), as well as
summation.
Situation 1: There are three simultaneously active synapses on the multipolar
neuron, two
producing EPSPs and one an IPSP. At least one of the EPSPs is larger than 15 mV
at the synapse. The neuron does NOT generate an action potential.
Situation 2: There are two simultaneously active synapses, one producing an EPSP
and the other an IPSP. The neuron generates an action potential.
Answer: (Note to instructor: It is best to have demonstrated this in class or on a
handout at some time prior to the exam.)
Diagrams and graphs should resemble those in Figure 8.7 in the chapter, except
that the number
of synaptic inputs shown will be greater (see Fig. 8.24), and a set of graphs should
be drawn for
each input. Diagrams of a multipolar neuron with the different synapses indicated
should be
produced. There should be a total of three to five synapses, depending on whether
or not the
student assumes the three synapses described for situation 1 are different from
those for situation
2. The graph of summation should resemble Figure 8.24c,d. In situation 1, the
student should
choose amplitudes that sum to a value below +15 mV (the PSP that was 15 mV at
the synapse is
smaller when it reaches the trigger zone). In situation 2, the student should choose
amplitudes that sum to a value equal to or above +15 mV.
Section: Integration of Neural Information Transfer
Learning Outcome: 8.14 Bloom’s Taxonomy: Application
218) We have finally discovered life on Venus. NASA scientists are investigating a
newly
discovered life form: a single-celled organism found in the swampy canals. You
have been
contracted by NASA to perform an electrophysiology study. Using intracellular
electrodes to
measure the electrical charge inside the cell, you find it has a resting membrane
potential of -45
mV when the outside fluid is arbitrarily set to 0 mV. Additionally, you have
determined ion concentrations and listed them below.
[ ] in
mOsm/L
Cell Swamp
K+ 5 150
Na+ 15 175
Cl- 40 40
For fun, you have used new molecular biology techniques to insert protein
channels into the cell membrane that allow only Na+ and Cl- to pass. Predict
which ion(s) will move. Tell what
direction it (they) will move and what force(s) is/are acting on it (them).
Answer: K+ cannot move because, without potassium channels, the membrane is
not permeable
to it. Na+ will move into the cell because both its chemical and electrical gradients
favor
movement in. Cl- leaves the cell due to the electrical gradient (the negative resting
potential repels it).
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Analysis
219) Use the Nernst equation to predict the membrane potential for each ion.
Answer: EK+ = 61 log 150/5 = 90.10 mV, ENa+ = 61 log 175/15 = 65.08 mV,
ECl- = -61 log
40/40 = 0 m
Section: Electrical Signals in Neurons Learning Outcome: 8.5
Bloom’s Taxonomy: Application
220) If an axon has an absolute refractory period of 2 msec, what is the maximum
frequency of action potential (AP) production in that neuron?
Answer: X AP/2 msec × 1000 msec/1 sec = 500 APs per second.
Section: Electrical Signals in Neurons
Learning Outcome: 8.4
Bloom’s Taxonomy: Analysis
221) Draw and label an action potential, in the form of a graph.
Answer: Graph should be similar to Figure 8.9 in the chapter.
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension
222) Draw a graph showing change in membrane permeability (don’t worry about
including the
units of permeability) to sodium and potassium during the course of an action
potential. For reference, superimpose a graph of the action potential.
Answer: Graph should resemble Figure 8.9 in the chapter.
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Comprehension 223) Draw a graph showing what would
happen to resting membrane potential over time, if the
sodium/potassium pump were not functioning. How would this affect a neuron’s
ability to
produce action potentials? What does this imply about the quantity of ions that
normally cross
the membrane during the course of an action potential?
Answer: It would be appropriate for the student to draw action potentials on the
graph beginning
at the point where the resting potential drifts up to threshold, and decreasing in
frequency as the
resting potential approaches. Very gradually, a cell’s resting membrane potential
would increase
until it reached and stabilized there. At that point the ions would be in equilibrium,
and no
further net flow of charge would occur. There would be no effect on ability to
generate action
potentials initially, but with the disappearance of the differential distribution of
sodium and
potassium upon which the action potential depends, action potentials would
gradually come to a
stop. This points out the fact that during any single action potential, so few ions
cross the
membrane that there is no significant change in ion concentrations. Thousands of
action potentials would be required before the absence of the sodium-potassium
pumps would be noticeable.
Section: Electrical Signals in Neurons
Learning Outcome: 8.8
Bloom’s Taxonomy: Application
224) The amplitude of an action potential depends in part on the amount of sodium
in the
extracellular fluid. Stanley Student has carefully impaled a neuron with an
intracellular electrode.
He tests the role of extracellular sodium by changing the concentration in the
bathing fluid and recording an action potential after each change. The data he
generated are shown in the table, where amplitude listed is the peak amplitude of
the action potential; make an appropriate graph.
Conc. Sodium (mOsM) Amp. (mV)
100 90 120
91 140 92
160 94 180
96
200 10
Answer:
Section: Electrical Signals in Neurons Learning Outcome: 8.4
Bloom’s Taxonomy: Application
225) Draw graphs showing the effects of hypokalemia and hyperkalemia on action
potential production. Don’t worry about exact millivolt values — the point is
to show that you understand the effects of these conditions relative to normal.
Answer: Graphs should resemble Figure 8.17 in the chapter.
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Application
226) In the graphs below, identify normokalemia, hyperkalemia, and hypokalemia.
Answer: See Figure 8.17 in the chapter.
Section: Electrical Signals in Neurons
Learning Outcome: 8.10
Bloom’s Taxonomy: Comprehension
227) Draw graphs showing the effect on action potentials in a cell following
effective doses of
each of the listed neurotoxins. Assume that the cell is normally brought to
threshold by an
electrical stimulus applied to it, so that any abnormality is due to the toxin. Precise
values for
voltage and duration are not important, just a general trend in how the action
potential may be different from normal.
1. puffer fish poison (blocks voltage-gated sodium channel activation)
2. tetraethylammonium (blocks voltage-gated potassium channels)
3. ouabain (blocks sodium-potassium pumps)
4. sea anemone toxin (blocks voltage-gated sodium channel inactivation)
Answer: 1. no action potential; membrane potential would show a stimulus pulse
that reaches threshold, however
2. prolonged action potential, as repolarization is slowed in absence of potassium
efflux;
peak may be higher as well
3. normal action potential
4. prolonged action potential, as sodium influx lasts longer; peak may be higher as
well
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.4
Bloom’s Taxonomy: Application
228) Draw graphs showing the effects on action potentials in a postsynaptic cell of
effective
doses for each of the listed toxins. Assume that the cell is normally brought to
threshold by the stimuli applied to its inputs, so that any abnormality is due
to the toxin.
1. curare (prevents receptor from binding neurotransmitter)
2. botulinum toxin (prevents neurotransmitter release)
Answer: In both cases, action potential is prevented, because the postsynaptic
potential is
blocked. Membrane potential would remain at resting potential, because even a
subthreshold postsynaptic potential fails to appear in the absence of
neurotransmitter action.
Section: Cell-to-Cell Communication in the Nervous System
Learning Outcome: 8.6
Bloom’s Taxonomy: Application
229) Explain the roles that the AMPA and NMDA receptors play in long-term
potentiation.
Answer: Both AMPA and NMDA receptors are located on the postsynaptic cells
(dendrites) and require binding of the excitatory neurotransmitter glutamate for
activation. When glutamate binds to the AMPA receptor, the channel opens and Na
enters the cell. This causes depolarization of the immediate postsynaptic cell or
dendrite. This depolarization causes Mg2+ ions to be “kicked out” of the NMDA
receptor channel; hence, Mg2+ is no longer acting as a channel blocker. If at the
same time glutamate is bound to the NMDA receptor then the channel gate is open
and Ca2+ enters the cell. The entry of Ca2+ triggers 2nd messenger pathways that
result in an increase in the number of glutamate receptors inserted into the post-
synaptic membrane. This increases the probability of an increase in the
postsynaptic response or depolarization to glutamate that is referred to as long-term
potentiation.
Section: Integration of Neural Information Transfer Learning Outcome: 8.9
Bloom’s Taxonomy: Comprehension
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