426
UNIT 3
Regulation and Integration of the Body
11
Multiple Choice/Matching
(Some questions have more than one correct answer. Select the best
answer or answers from the choices given.)
1.
Which of the following structures is not part of the central
nervous system?
(a)
the brain,
(b)
a nerve,
(c)
the spinal cord,
(d)
a tract.
2.
Match the names of the supporting cells found in column B with
the appropriate descriptions in column A.
Column A
____ (1)
myelinates nerve fibers
in the CNS
____ (2)
lines brain cavities
____ (3)
myelinates nerve fibers
in the PNS
____ (4)
CNS phagocyte
____ (5)
helps regulate the ionic
composition of CNS
extracellular fluid
12.
Identify the neuronal circuits described by choosing the correct
response from the key.
Key:
(a)
converging
(b)
diverging
Review Questions
Column B
(a)
astrocyte
(b)
ependymal cell
(c)
microglial cell
(d)
oligodendrocyte
(e)
satellite cell
(f)
Schwann cell
3.
What type of current flows through the axolemma during the
steep phase of repolarization?
(a)
chiefly a sodium current,
(b)
chiefly a potassium current,
(c)
sodium and potassium
currents of approximately the same magnitude.
4.
Assume that an EPSP is being generated on the dendritic
membrane. Which will occur?
(a)
specific Na
1
channels will open,
(b)
specific K
1
channels will open,
(c)
a single type of channel
will open, permitting simultaneous flow of Na
1
and K
1
,
(d)
Na
1
channels will open first and then close as K
1
channels open.
5.
Te velocity of nerve impulse conduction is greatest in
(a)
heavily
myelinated, large-diameter fibers,
(b)
myelinated, small-diameter
fibers,
(c)
nonmyelinated, small-diameter fibers,
(d)
nonmyelinated, large-diameter fibers.
6.
Chemical synapses are characterized by all of the following
except
(a)
the release of neurotransmitter by the presynaptic
membranes,
(b)
postsynaptic membranes bearing receptors that
bind neurotransmitter,
(c)
ions flowing through protein channels
from the presynaptic to the postsynaptic neuron,
(d)
a fluid-filled
gap separating the neurons.
7.
Biogenic amine neurotransmitters include all but
(a)
norepin-
ephrine,
(b)
acetylcholine,
(c)
dopamine,
(d)
serotonin.
8.
Te neuropeptides that act as natural opiates are
(a)
substance P,
(b)
somatostatin and cholecystokinin,
(c)
tachykinins,
(d)
enkephalins.
9.
Inhibition of acetylcholinesterase by poisoning blocks
neurotransmission at the neuromuscular junction because
(a)
ACh is no longer released by the presynaptic terminal,
(b)
ACh synthesis in the presynaptic terminal is blocked,
(c)
ACh
is not degraded, hence prolonged depolarization is enforced on
the postsynaptic cell,
(d)
ACh is blocked from attaching to the
postsynaptic ACh receptors.
10.
Te anatomical region of a multipolar neuron that has the lowest
threshold for generating an AP is the
(a)
soma,
(b)
dendrites,
(c)
axon hillock,
(d)
distal axon.
11.
An IPSP is inhibitory because
(a)
it hyperpolarizes the
postsynaptic membrane,
(b)
it reduces the amount of
neurotransmitter released by the presynaptic terminal,
(c)
it prevents calcium ion entry into the presynaptic terminal,
(d)
it changes the threshold of the neuron.
(c)
parallel aFer-discharge
(d)
reverberating
____ (1)
Impulses continue around and around the circuit until
one neuron stops firing.
____ (2)
One or a few inputs ultimately influence large numbers
of neurons.
____ (3)
Many neurons influence a few neurons.
____ (4)
May be involved in exacting types of mental activity.
Short Answer Essay Questions
13.
Explain both the anatomical and functional divisions of the
nervous system. Include the subdivisions of each.
14.
(a) Describe the composition and function of the cell body.
(b) How are axons and dendrites alike? In what ways (structurally
and functionally) do they differ?
15.
(a) What is myelin? (b) How does the myelination process differ
in the CNS and PNS?
16.
(a) Contrast unipolar, bipolar, and multipolar neurons
structurally. (b) Indicate where each is most likely to be found.
17.
What is the polarized membrane state? How is it maintained?
(Note the relative roles of both passive and active mechanisms.)
18.
Describe the events that must occur to generate an AP. Relate
the sequence of changes in permeability to changes in the ion
channels, and explain why the AP is an all-or-none phenomenon.
19.
Since all APs generated by a given nerve fiber have the same
magnitude, how does the CNS “know” whether a stimulus is
strong or weak?
20.
(a) Explain the difference between an EPSP and an IPSP.
(b) What specifically determines whether an EPSP or IPSP will
be generated at the postsynaptic membrane?
21.
Since at any moment a neuron is likely to have thousands
of neurons releasing neurotransmitters at its surface, how is
neuronal activity (to fire or not to fire) determined?
22.
Te effects of neurotransmitter binding are very brief. Explain.
23.
During a neurobiology lecture, a professor repeatedly refers
to group A and group B fibers, absolute refractory period, and
myelin sheath gaps. Define these terms.
24.
Distinguish between serial and parallel processing.
25.
Briefly describe the three stages of neuron development.
26.
What factors appear to guide the outgrowth of an axon and its
ability to make the “correct” synaptic contacts?
Critical Thinking
and Clinical Application
Questions
1.
Mr. Miller is hospitalized for cardiac problems. Somehow,
medical orders are mixed up and Mr. Miller is infused with a
K
1
-enhanced intravenous solution meant for another patient
who is taking potassium-wasting diuretics (i.e., drugs that cause
excessive loss of potassium from the body in urine). Mr. Miller’s
potassium levels are normal before the IV is administered. What
do you think will happen to Mr. Miller’s resting membrane
potentials? ±o his neurons’ ability to generate APs?
2.
Local anesthetics block voltage-gated Na
1
channels. General
anesthetics are thought to activate chemically gated Cl
2
channels,
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