Name: __________________________
Biology 449 - Animal Physiology
Fall 2011
Midterm 1 – Key
Fill in your scantron form as follows:
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Write and bubble in your name in the upper left (last name first).
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.
1. Which of the following descriptions best characterizes Claude Bernard?
a. “The father of modern physiology”
b. “The guy with the peas”
c. “Darwin’s bulldog”
d. “Napoleon’s caddy”
e. “The crotchety veterinarian with a heart of gold”
2. Consider a scenario in which the concentration of a physiologically regulated substance falls
below its setpoint. Which of the following would be a useful response?
a.
b.
c.
d.
e.
Increasing the influx of the substance
Increasing the efflux of the substance
Decreasing the efflux of the substance
a and b
a and c
3. In physiological systems, positive feedback loops
a.
b.
c.
d.
e.
are the most common type of feedback loop.
are used to predict a change in a variable before it occurs.
must ultimately be shut down to avoid runaway changes in a variable.
are only found in neurons.
help boost the self-esteem of control pathways.
4. The Fick equation is very useful for determining the rate of diffusion of a substance, except
that it doesn’t incorporate the effects of
a.
b.
c.
d.
e.
the charge (or valance) of the substance.
the difference in the concentration of the substance between the two sides.
the distance the substance has to diffuse.
the surface area over which diffusion occurs.
All of the above are part of the Fick equation.
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5. A substance will have an easier time crossing a cell membrane by simple diffusion the
_______________ it is.
a.
b.
c.
d.
e.
bigger
more charged
more lipophilic
Two of the above make it easier to cross a cell membrane.
All of the above make it easier to cross a cell membrane.
6. Which of the following statements regarding the movement of water molecules across a cell
membrane is true?
a. Aquaporins move water across membranes through primary active transport.
b. Water can be moved against its concentration gradient by cotransport with Na+ in a
carrier protein.
c. The movement of water across a cell membrane generates a membrane voltage.
d. Water can be moved across cell membranes against an overall osmotic gradient
by manipulating local osmolarities in a favorable direction.
e. Water never crosses cell membranes in any way.
7. The spinal cord is part of the
a.
b.
c.
d.
e.
afferent nervous system.
autonomic nervous system.
central nervous system.
enteric nervous system.
somatic nervous system.
8. A type of glial cell that provides myelination of neurons is the
a.
b.
c.
d.
e.
astrocytes.
ependymal cells.
interneurons.
microglia.
Schwann cells.
9. The reason that a cell membrane at rest has a membrane potential of about -70mV is that
a.
b.
c.
d.
e.
only K+ can cross the membrane.
only Na+ can cross the membrane.
the membrane is more permeable to K+ than Na+.
the membrane is more permeable to Na+ than K+.
the membrane is equally permeable to both ions.
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10. When an axon first reaches threshold potential, the voltage-gated Na+ channels show which
of the following responses?
a.
b.
c.
d.
e.
Activation gates quickly open; inactivation gates slowly close.
Activation gates quickly close; inactivation gates slowly open.
Activation gates slowly open; inactivation gates quickly close.
Activation gates slowly close; inactivation gates quickly open.
They puff up like popcorn.
11. Imagine that the normal voltage-gated K+ channels in an axon are replaced with an altered
form that open quickly, rather than slowly, once threshold is reached. (They still close
slowly.) Which of the following might be expected to happen?
a.
b.
c.
d.
e.
The action potential would have a higher peak voltage than normal.
The action potential would have a lower peak voltage than normal.
The membrane would stay depolarized for much longer than normal.
K+ would flow into the cell rather than out of it.
The cable properties of the axon would improve.
12. Recall that Cl- levels are higher outside of cells than within. A neurotransmitter than that
opened Cl- channels would have
a.
b.
c.
d.
e.
no effect on membrane voltage.
excitatory effects.
inhibitory effects.
supernatural effects.
potentially serious side effects, including spontaneous exsanguination, limb
autotomization, and the hallucination that you are a physiology student.
13. The process of spatial summation
a.
b.
c.
d.
e.
can only depolarize postsynaptic neurons.
can only hyperpolarize postsynaptic neurons.
must involve only one neuron.
must involve only two neurons.
None of the above is true.
14. A tonic receptor is a sensory cell that
a.
b.
c.
d.
e.
shows rapid adaptation to a continuous level of stimulation.
shows little or no adaptation to continuous level of stimulation.
shows a large dynamic range.
shows a small dynamic range.
shows range fractionation.
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15. If we say that a sensory cell has a small receptive field, we mean
a.
b.
c.
d.
e.
it detects stimuli over only a small amount of surface area or volume.
it can respond to only a narrow range of stimulus intensities.
it can inhibit adjacent afferent neurons.
it does not respond to painful levels of stimulation.
it responds to only a few stimulus modalities.
16. A person lacking hair cells would be unable to
a.
b.
c.
d.
e.
detect linear acceleration.
detect rotational movements.
detect vibrations through her skin.
Two of the above. (a and b)
All of the above.
17. Which of the following give the correct order of transfer of sound energy in the human ear?
a.
b.
c.
d.
e.
Middle ear ossicles, oval window, tympanic membrane, tectorial membrane
Oval window, middle ear ossicles, tectorial membrane, tympanic membrane
Tympanic membrane, middle ear ossicles, oval window, tectorial membrane
Tectorial membrane, oval window, tectorial tympanic, middle ear ossicles
Tectorial membrane, middle ear ossicles, oval window, tympanic membrane
18. Imagine that a virus attacks the cochlea of an individual’s ear, killing all the hair cells in the
distal half (the end closest to the tip rather than the base). This ear would have a hard time
detecting
a.
b.
c.
d.
e.
sounds of high volume (loud sounds).
sounds of low volume (quiet sounds).
sounds of high frequency (high-pitched sounds).
sounds of low frequency (low-pitched sounds).
sound of any kind.
19. The human eye relies on refraction of light to focus images. This refraction is accomplished
by the
a.
b.
c.
d.
e.
cornea.
iris.
lens.
a and c
b and c
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20. Which of the following statements about rod photoreceptors is incorrect?
a.
b.
c.
d.
e.
Rods are depolarized when exposed to light.
Retinal is converted from the cis to trans form when struck by light.
Activated phosphodiesterase converts cGMP to 5’-GMP.
Phosphodiesterase is activated by transducin.
The ability of opsin to activate transducin depends on the form of the associated
retinal.
Short answer: 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.
Some answers in this section are summary versions that indicate the general nature of the
expected answer rather than all the details necessary to receive full credit.
21. Oxygen delivery to tissues in your body is obviously important, and if oxygen levels in your
blood drop too low, certain responses are seen. Oxygen levels in your blood match the levels
in your lungs, so low oxygen levels in the blood lead to an increase in ventilation (breathing)
to increase oxygen levels in the lungs (and hence blood). Ventilation is controlled by the
medulla through nerves in the somatic nervous system. The medulla receives information on
current oxygen levels through afferent neurons coming from chemoreceptors in the
circulatory system.
Based on this description, identify each of the following components in the negative
feedback loop controlling oxygen levels:
Sensor: Chemoreceptor (for oxygen)
Afferent pathway: Afferent neurons
Integrating center: Medulla
Efferent pathway: Somatic nerves
Effector: Lungs, or ventilation of lungs
Regulated variable: Blood oxygen levels
22. Consider our dear old friends, solution A and solution B. They are, of course, separated by a
semipermeable membrane.
a. The membrane is permeable only to water. If A is a 100 mMol solution of urea, and B is a
100 mMol solution of NaCl, which way will the water move, and why?
100 mMol urea = 100 mOsm
100 mMol NaCl = 200 mOsm
Water will move from A to B because of the higher osmolarity in B
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b. This time, A is a 100 mMol solution of urea, and B is a 100 mMol solution of glucose. The
membrane is permeable to urea as well as water. How will each substance move in this
system, and why?
Initially, both sides are 100 mOsm
Urea will diffuse down its concentration gradient from A to B, increasing osmolarity in
B. Water will follow along the osmotic gradient as a result.
23. Describe the mechanism by which action potentials propagate along an unmyelinated axon.
Explain what keeps the action potential propagating in a single direction.
Each AP depolarizes adjacent regions of the membrane; regions raised above threshold
will then show AP’s of their own, which trigger further AP’s. AP’s cannot propagate in
the “backwards” direction because those regions are in the refractory period and
cannot undergo AP’s.
24. Describe the process of synaptic transmission for a chemical synapse. Assume the
postsynaptic neuron has ionotropic receptors that allow Na+ influx when activated. Your
description should begin with the arrival of the action potential at the presynaptic terminal,
and end with a qualitative description of the effects on the postsynaptic neuron. You do not
need to describe what happens to the neurotransmitter after it binds to the receptors.
AP arriving at the terminal causes opening of VG Ca2+ channels. Ca2+ influx releases
synaptic vesicles from cytoskeleton; these bind to docking proteins and release NT into
the synaptic cleft. NT diffuses across cleft to receptors in postsynaptic neuron, binding
to them and causing them to open. Na+ entry depolarizes/excites the postsynaptic
membrane.
25. Name the five known types of taste reception and indicate the particular chemical or class of
chemicals each senses. Choose one well-characterized receptor mechanism and describe
how it works.
Salt – Na+
Sweet – Sugars
Sour – H+
Umami – Amino acids
Bitter – Toxic and other substances (this answer was expected to be vague)
The description will depend on the tastant selected, but an obvious choice is salt. Na+
enters through channel proteins, depolarizing the membrane. This opens VG Ca2+
channels, allowing Ca2+ influx, which causes NT release from the taste receptor by the
same mechanism described for neural synapses above.
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