| Biology 449 - Animal Physiology | Spring 2004 |
Midterm 1 - Key
Answers in italics
Multiple choice: As always, choose the best answer for each multiple-choice question. Answer on your scantron form. Each question (except #1) is worth 3 points.
1. Fill in your scantron form: (1 point)
· Write and bubble in your name in the upper left (last name first).
· If you wish to retrieve your exam score through the course web site, write and bubble in a secret code (i.e. a password) in the “Special Codes” section. Be sure you remember it!
· Follow any additional instructions provided in class.
· Sign your form in the upper right.
a. I swear I did it all just like you asked.
b. – e. I laugh at your free point!
2. The noun “homeostasis” is closest in meaning to which of the following terms?
a. “The internal environment”
b. “Regulation”
c. “Negative feedback loop”
d. “Positive feedback loop”
e. “Donnan equilibrium”
3. With regard to thermoregulation in humans, which of the following mechanisms will tend to decrease the rate of heat loss a person experiences?
a. Increased shivering.
b. Increased sweating.
c. Decreased blood flow to the skin.
d. Decreased metabolic rate.
e. Two of the above.
4. In healthy people, if the level of glucose in the blood increases above normal levels, a group of cells in the pancreas known as beta cells begin to secrete the hormone insulin in larger amounts. Among other effects, increased insulin causes most cells in the body to begin using more glucose for metabolism, helping to decrease blood sugar levels. In this negative feedback system, glucose is
a. the afferent pathway.
b. the integrating center.
c. the efferent pathway.
d. the effector.
e. the regulated variable.
5. The Fick equation takes into account all of the following except
a. the distance across which diffusion takes place.
b. the difference in concentration between the two volumes.
c. the surface area over which diffusion takes place.
d. the charge of the diffusing particles.
e. Two of the above.
6. Two volumes of water, A and B, each contain a number of ions and are separated by a membrane impermeable to water. If the concentration of Na+ is higher in A than B, and the membrane is permeable to Na+, we know that
a. Na+ will show net diffusion from A to B.
b. Na+ will show net diffusion from B to A.
c. Na+ will show no net diffusion.
d. Either a or c.
e. It is impossible to say without more information.
7. Two volumes of water, A and B, are “exposed” to one another across a membrane permeable to water. If water moves from A to B, we can say with certainty that at the start of the experiment
a. A was hyperosmotic relative to B
b. A was hyposmotic relative to B
c. A was hypertonic relative to B
d. A was hypotonic relative to B
e. Two of the above.
8. Which of the following is true about carrier proteins in the cell membrane?
a. They only move substances down their concentration gradients.
b. They always require ATP.
c. They are involved in secondary active transport.
d. They are involved in permeation.
e. They may be ionotropic or metabotropic.
9. The coordination of muscular activity takes place mainly in the
a. thalamus.
b. hypothalamus.
c. cerebellum.
d. cerebrum.
e. brainstem.
10. The glial cells probably
a. do nothing of importance.
b. just serve as insulators for axons.
c. just clean up foreign material in the nervous system.
d. do much more than was thought just ten years ago.
e. b and c.
11. Based on the information you learned in class, the generation of a potential across a cell membrane requires that the membrane is permeable to at least how many ions?
a. Zero.
b. One.
c. Two.
d. Three.
e. It depends on the valance of the ions.
12. During a normal action potential, the hyperpolarization of the membrane is the result of
a. Na+ channels opening.
b. Na+ channels closing.
c. K+ channels opening.
d. K+ channels closing.
e. elastic recoil.
13. You have an isolated neuron in a bath of artificial body fluid, so that it can generate normal action potentials. You then add a mystery substance, X, to the fluid, and when you trigger the next action potential you see that the cell membrane stays depolarized indefinitely. Which of the following might explain this?
a. X interferes with normal opening of voltage-gated Na+ channels.
b. X interferes with normal closing of voltage-gated Na+ channels.
c. X interferes with normal opening of voltage-gated K+ channels.
d. X interferes with normal closing of voltage-gated K+ channels.
e. Two of the above.
14. Which of the following would be least likely to increase the speed of action potential propagation in an axon?
a. Improving the cable properties of the axon.
b. Increasing the axon diameter.
c. Saltatory conduction.
d. Myelination.
e. Decreased refractory period.
15. Gap junctions could best be described as
a. ionotropic receptors
b. metabotropic receptors.
c. G-proteins.
d. spaces between Schwann cells.
e. pores.
16. If the amount of neurotransmitter released by a pre-synaptic neuron were increased, which of the following would you always expect to be true?
a. The post-synaptic neuron should become more depolarized than it normally would.
b. The post-synaptic neuron should become more hyperpolarized than it normally would.
c. More ion channels would be open in the post-synaptic membrane.
d. More ion channels would be closed in the post-synaptic membrane.
e. More receptor proteins would be activated in the post-synaptic membrane.
17. Spatial summation is best defined as
a. The cumulative effect of multiple epsp’s from a single presynaptic neuron.
b. The cumulative effect of multiple ipsp’s from a single presynaptic neuron.
c. The cumulative effect of multiple epsp’s from two or more presynaptic neurons.
d. The cumulative effect of multiple ipsp’s from two or more presynaptic neurons.
e. The cumulative effect of multiple epsp’s and/or ipsp’s from two or more presynaptic neurons.
18. Which of the following would be classified as an amino acid neurotransmitter?
a. Dopamine
b. Glutamate
c. Acetylcholine
d. Epinephrine
e. Enkephalin
19. One effective mechanism discussed in class for amplifying the response a receptor cell shows to a small stimulus involves
a. increasing the size of the receptor membrane region of the cell.
b. making the receptor membrane thinner.
c. using a G-protein complex to initiate a cascade of enzyme activation.
d. increasing the diameter of the axon carrying the transduced signal.
e. increasing the length of the axon carrying the transduced signal.
20. A tonic neural receptor would typically show its strongest response to
a. a weak stimulus.
b. an intermediate stimulus.
c. a strong stimulus.
d. a sudden increase in the stimulus.
e. a sudden decrease in the stimulus.
21. Which type of taste receptor might have neurotransmitter release triggered by either the blockage of K+ channels or the release of intracellular calcium stores?
a. Salt.
b. Sour.
c. Sweet.
d. Bitter.
e. All of the above.
22. Otoliths are part of a sensory system that responds primarily to
a. linear velocity.
b. linear acceleration.
c. rotational velocity.
d. rotational acceleration.
e. the sound of fingernails on a blackboard.
23. The hair cells of the cochlea are stimulated most directly by
a. the movements of the bone of the middle ear.
b. the movements of the oval window.
c. the expansion and contraction of the cochlea.
d. the changes in pressure in the cochlear fluid.
e. the movements of the tectorial membrane.
24. If a glandular tissue secretes a fluid it would be classified as a(n)
a. autocrine gland.
b. endocrine gland.
c. exocrine gland.
d. paracrine gland.
e. really disgusting gland.
25. Intracellular receptors for lipophilic hormones, once activated, have their effect by
a. activating G-protein complexes.
b. serving as modifiers of enzymes that control metabolic processes.
c. activating or deactivating proteins that control translation rates.
d. blocking pores in the nuclear membrane to prevent movement of RNA.
e. attaching to DNA and controlling gene expression.
26. The hormones released be the anterior pituitary would be classified as
a. glandular hormones.
b. neurohormones.
c. neurosecretory hormones.
d. exocrine products.
e. autocrine agents.
Short answer: Write
a concise answer to each of the following questions. Your answers should fit
in the spaces provided. Each question is worth 4 points.
27. The major fluid volume of the vertebrate body (including humans) can be divided into two major compartments. Below, provide the names of these two major compartments, and for each indicate whether the each indicated ion is found in high or low concentration.
Compartment Na+ K+ Cl-
Intracellular fluid Low High Low
Extracellular fluid High Low High
28. Explain
what a feed-forward system is, and give an example, either biological or
man-made.
A feed-forward system is one that allows a negative feedback loop (in other
words, a regulatory system) to anticipate changes before they occur. It would
typically involve a sensor that monitors something other than the primary
regulated variable, where this second variable would typically change before
the regulated variable. The example from lecture concerns thermoregulation. The
main regulated variable is core body/blood temperature. However, temperature
sensors in the skin respond more directly to air temperature, and a change in
air temperature would typically precede a change in body temperature.
29. Describe the process of synaptic transmission in a typical fast chemical synapse. A diagram may be helpful, but be sure you explain what is occurring. You do not need to discuss the issues of neural integration or summation.
When an action
potential arrives at the pre-synaptic neuron, it triggers the opening of voltage-gated
Ca2+ channels, which allows Ca2+ to enter the cytosol.
The increase in intracellular Ca2+ causes synaptic vesicles containing
neurotransmitter to fuse with the cell membrane adjacent to the synaptic cleft.
The released neurotransmitter diffuses across the cleft and binds to receptor
proteins, triggering, for example, the opening of Na+ channels.
These effects on ion channels are direct (ionotropic) in the case of fast
synapses (versus indirect or metabotropic in the case of slow synapses), and
can trigger excitatory or inhibitory post-synaptic potentials. The receptor
proteins are “turned off” again when neurotransmitter levels in the cleft
drop, due to diffusionary loss, reuptake, or enzymatic breakdown.
30. In the nervous system, how is information encoded when it is sent along the axon? (For example, how does a sensory neuron carry information about the strength of the stimulus affecting it?) What makes this system the only practical one for encoding this information, given the nature of axon function?
Information is coded via the frequency of
action potentials traveling down the axon. The reason for this is that action
potentials are more-or-less invariant in both voltage change (i.e. the amount
of depolarization) and duration. Because of this, individual action potentials
cannot carry any useful information. Only the frequency with which those
action potentials occur can be used as the “code” that signals stimulus strength,
for example.
31. Describe the process of light transduction in a rod cell, up to the point of neurotransmitter release from the cell. Again, a diagram may be helpful, but be sure you explain what is occurring.
In the dark,
retinal is in its cis form and in this state can bind to opsin. Under
these conditions, cGMP is present in higher levels in the cell and activates
special Na+ channels, so Na+ ions can enter the
photoreceptor and depolarize it. This depolarization causes the release of
relatively large amounts of neurotransmitter.
In the light, the
retinal is changes to the trans form and dissociates from the opsin.
The opsin then actives transducin, which in turn activates phosphodiesterase.
The PDE then converts cGMP into 5’-GMP, causing Na+ channels to
close. The decreased Na+ permeability causes the membrane to hyperpolarize,
reducing the rate of neurotransmitter release.
32. Fill
in the following table for the hypothalamic-pituitary system with the
appropriate hormones or effects. (Note that this is not a complete table.) Be
sure to use the full names of each hormone, not the abbreviations. You may,
however, use “h.” for “hormone.”
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Target Organ/Tissue |
Gonadotropin releasing h. |
  |
Follicle stimulating h. |
 |
Gonads |
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Luteinizing h. |
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Corticotropin relasing h. |
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Adrenocorticotropic h. |
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Adrenal cortex |
Thyrotropin releasing h. |
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Thyroid stimulating h. |
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Thyroid gland |
Somatostatin |
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Inhibits growth h. |
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