Name: __________________________
Biology 449 - Animal Physiology
Spring 2008
Midterm 1
Fill in your scantron form as follows:
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Write and bubble in your name in the upper left (last name first).
Follow any additional instructions provided in class.
Sign your form on the upper right. By so doing you verify that you are abiding
by Creighton’s policy on academic honesty.
Multiple choice: As always, choose the best answer for each multiple-choice question.
Answer on your scantron form. Each question is worth 3 points.
Which if the following ideas was one of Claude Bernard’s important contributions to the
development of physiological thought?
a.
b.
c.
d.
e.
Many body cells have to deal directly with the external environment.
The body’s internal environment is actively regulated.
Most mammals rely primarily on behavioral regulation to control body temperature.
Positive feedback loops are very common in physiological systems.
Dogs shouldn’t eat sugary snacks.
Consider the regulation of sodium levels in an animal. If Na+ levels begin to increase, which of
the following responses might be seen?
i. increased Na+ influx
iii. increased Na+ efflux
f.
g.
h.
i.
j.
ii. decreased Na+ influx
iv. decreased Na+ efflux
i and iii
i and iv
ii and iii ←
ii and iv
None of the above.
In a positive feedback loop, if a variable decreases slightly from its initial (or reference) value,
then
k.
l.
m.
n.
o.
it will be returned to its initial value.
it will decrease further and further from its initial value.
it will increase above its initial value, becoming greater and greater.
it will oscillate between negative and positive deviations from its intial value.
it will remain at its new value indefinitely.
1
Which of the following is not true about the rate of diffusion of an uncharged particle X from one
location to another?
p.
q.
r.
s.
t.
The rate is influenced by the surface area for diffusion.
The rate is influenced by the thickness of the barrier to diffusion.
The rate is influenced by the concentration difference in X between the two locations.
The rate is influenced by the concentration of other particles in the two locations.
All of the above are true.
Two isosmotic solutions are put on either side of a membrane that is permeable to water. Which
of the following could by itself result in the movement of water from the solution on one side
of the membrane to the other?
u.
v.
w.
x.
y.
The molecular weight of the solutes is higher on one side than the other.
The solutes on one side are ionic and the others are not.
One of the solutes shows net diffusion from one side to the other.
The hydrostatic pressure is higher on one side than the other.
Two of the above could cause water to move from one side to the other. (c and d)
As seen in the examples we have encountered so far in lecture, the movement of small ions like
sodium and potassium down their concentration gradient across a cell membrane is mainly
via
z. simple diffusion through the lipid bilayer.
aa. permeation through channel proteins.
bb. facilitated transport through carrier proteins.
cc. primary active transport through carrier proteins.
dd. secondary active transport through carrier proteins.
The component of the peripheral nervous system that brings information from sensory receptors
to the central nervous system is the
ee. afferent division.
ff. autonomic nervous system.
gg. efferent division.
hh. enteric nervous system.
ii. somatic nervous system.
Which of the following provides myelination for the central nervous system?
jj. Astrocytes
kk. Ependymal cells
ll. Microglia
mm. Oligodendrocytes
nn. Upholstrocytes
2
If a typical cell membrane at its normal resting potential is given a brief (1 ms) negative stimulus
to hyperpolarize it, and then nothing else is done to the membrane,
oo. it will tend to return to its normal resting potential fairly quickly (a few milliseconds).
pp. it will return to its normal resting potential after a long delay (several minutes).
qq. it will stay hyperpolarized at the same voltage indefinitely.
rr. it will become more and more hyperpolarized as time goes on.
ss. it will show a compensatory depolarization above its normal resting potential.
The rapid decline in membrane voltage seen during the repolarization phase of an action
potential is due in large part to
tt. the opening of voltage-gated sodium channels when their activation gates open.
uu. the closing of voltage-gated sodium channels when their activation gates close.
vv. the closing of voltage-gated sodium channels when their inactivation gates close.
ww. the closing of voltage-gated sodium channels when the membrane drops below
threshold.
xx. the closing of potassium channels when the membrane drops below threshold.
In the context of neurons, the “relative refractory period” is
yy. the period when the membrane is repolarizing following the peak of the action
potential.
zz. the period following an action potential when another action potential cannot be
initiated.
aaa. the period following an action potential when another action potential can only
be initiated with difficulty (i.e. the threshold potential is higher).
bbb. the period when neurotransmitter levels in the synaptic cleft are declining.
ccc. the period when G-proteins are being reset to their resting state.
The reason action potential propagation is faster in a myelinated axon than in an unmyelinated
axon is because in myelinated axons
ddd. action potentials have higher peak voltages.
eee. voltage-gated sodium channels open more quickly.
fff. voltage-gated potassium channels open more quickly.
ggg. action potentials don’t occur in the myelinated regions.
hhh. each action potential depolarizes a greater length of axon above threshold.
Which of the following would have inhibitory (i.e. hyperpolarizing) effects on a post-synaptic
neuron?
iii. An increased influx of positive ions.
jjj. A decreased influx of positive ions.
kkk. A decreased efflux of positive ions.
lll. An increased efflux of negative ions.
mmm. Two of the above would have inhibitory effects on the neuron.
3
Consider two presynaptic excitatory neurons, A and B, that synapse with a postsynaptic neuron
Z. B has a greater excitatory effect than A. If action potentials arrive at the axon terminal of
A and B at the same time, which of the following best describes the effect on Z?
nnn. The excitatory effect would be equal to that of A alone.
ooo. The excitatory effect would be equal to that of B alone.
ppp. The excitatory effect would be the sum of those of A and B.
qqq. The excitatory effect would be the difference of those of A and B.
rrr. The excitatory effect would be the multiple of those of A and B.
Which of the following is an unmodified amino acid that acts as a neurotransmitter?
sss. Acetylcholine
ttt. Dopamine
uuu. Epinephrine
vvv. Glutamate
www. Serotonin
A receptor cell that shows little or no adaptation to a stimulus of constant intensity would be
labeled as
xxx.
yyy.
zzz.
aaaa.
bbbb.
a baroreceptor.
a mechanoreceptor.
a phasic receptor.
a proprioceptor.
a tonic receptor.
The otolith organs (the utricle and the saccule) rely on which characteristic of the otoliths being
different than the surrounding tissue?
cccc.
dddd.
eeee.
ffff.
gggg.
Electrical charge
Color
Density
Reduction potential
Size
When the oval window of the inner ear moves, it most directly affects the pressure in the
hhhh. scala media.
iiii. scala typmani.
jjjj. scala vestibuli.
kkkk. tectorial membrane.
llll. tympanic membrane.
4
A person is listening to a series of electronically generated tones. Consider the set of hairs cells
in the organ of Corti that respond the most strongly to the first tone. If the stereocilia of these
hair cells are being bent more and more with each new tone, this would mean the sound is
changing in what way?
mmmm. The duration of the tones was increasing.
nnnn. The frequency of the tones was increasing.
oooo. The vibrato or “warbling” of the tones was increasing.
pppp. The volume of the tones was increasing.
qqqq. The tones aren’t changing, but the listener’s anticipation of the tones is.
Consider a rod-type photoreceptor with a mutant form of transducin that cannot activate
phosphodiesterase under any circumstances. Which of the following statements about this
photoreceptor would most likely be true?
rrrr. It would show the normal depolarized state in the dark, and stay depolarized in
the light.
ssss. It would show the normal hyperpolarized state in the dark, and stay
hyperpolarized in the light.
tttt. It would show the normal depolarized state in the light, and stay depolarized in the
dark.
uuuu. It would show the normal hyperpolarized state in the light, and stay
hyperpolarized in the dark.
vvvv. The process of phototransduction would reverse, and it would begin glowing.
Short answer begins on the next page. Write a concise answer to each of the following
questions. Your answers should fit in the spaces provided. Diagrams are welcome but
must be accompanied by written explanations. Each question is worth 8 points.
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2. Using any negative feedback loop we have discussed in class, describe how the loop works,
and label the components with their role in the loop (effector, etc.). Two notes: First, you
don’t need to label any components that weren’t identified in lecture (i.e. it may not be
possible to individually identify all the parts of a loop in every example). Second, you need
only describe one effector, even if multiple ones are involved in the loop.
3. The answers to the following two questions should involve verbal descriptions rather than
mathematical calculations. If you are unsure what is meant by this, please ask!
a. What is the main difference between the Nernst equation and the Goldmann equation? In
other words, what is each good for?
b. Explain (again in qualitative rather than quantitative terms) why resting membrane potentials
for vertebrate cells are usually about -70mv. In other words, why aren’t they zero or
+70mV?
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4. Describe the process of synaptic transmission for a chemical synapse with ionotropic
receptors. Addendum provided during exam: Start from the arrival of the AP at the
presynaptic axon terminal and end at the point at which the ionotropic receptors are
activated. You do not need to discuss what happens to the NT after this point.
5. Explain what is meant by the dynamic range of a sensory receptor. Explain also how range
fractionation is used to help compensate for limitations in this range, and provide an example
of fractionation.
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6. Choose two of the following three classes of taste receptors and explain one of the
transduction mechanisms found in that class: salt, sour, bitter.
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