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Biology 449 - Animal Physiology |
Fall 2005 |
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 is worth 2˝ points.
1. One of these things is not like the others…One of these things just doesn’t belong… Which of these fluids would be considered to have a very different ionic composition than the other three?
a. Intracellular fluid.
b. Extracellular fluid.
c. Interstitial fluid.
d. Blood plasma.
e. All of these fluids have very similar ionic composition.
2. When we say that an organism is an open system, we mean that
a. the organism is acellular.
b. the organism cannot differ chemically from the environment.
c. matter and energy can enter and leave the organism.
d. the organism exhibits regulation.
e. the organism likes to share its feelings.
3. During exercise, there is an increase in heart rate to support increased blood flow to working muscles as their oxygen use increases. If the anticipation of exercise caused an increase in heart rate shortly before exercise actually began, this would most likely be an example of
a. a negative feedback loop.
b. a positive feedback loop.
c. a setpoint change.
d. an on/off response.
e. a feedforward mechanism.
4. A lizard maintaining its body temperature by moving in and out of the sun would be engaging in
a. physiological regulation.
b. behavioral regulation.
c. anatomical regulation.
d. conformation.
e. Two of the above.
5. In the Fick equation, the term in the denominator is
a. the distance of diffusion.
b. the area of diffusion.
c. the net diffusion flux.
d. the permeability constant.
e. the difference in concentration.
6. A 1.0M solution of KCl is on one side of a membrane (side A) while a 1.0M solution of NaCl is on the other side (side B). If the membrane is equally permeable to K+ and Na+ then we would expect that
a. there would be a movement of K+ to side B but no net movement of Na+.
b. there would be a movement of Na+ to side A but no net movement of K+.
c. there would be movement of a small amount of both K+ and Na+ until counteracted by the appearance of a charge across the membrane.
d. there would be movement of both K+ and Na+ until the concentration of each was equal on both sides.
e. there would be no net movement of K+ or Na+.
7. If we know that solution A is hypertonic relative to solution B, then we know that
a. A is hyperosmotic relative to B.
b. A is isosmotic relative to B.
c. water will move from A to B if the barrier is water permeable.
d. water will move from B to A if the barrier is water permeable.
e. Two of the above.
8. The molecule that would most easily pass through a cell membrane would be one that was
a. large.
b. charged.
c. ionic.
d. hydrophilic.
e. lipophilic.
9. Heart rate is controlled by the
a. cerebellum
b. thalamus
c. hypothalamus.
d. brain stem.
e. spinal cord.
10. Action potentials in a neuron normally appear in the
a. dendrites.
b. soma.
c. axon.
d. b and c.
e. a, b, and c.
11. You would use the Goldman equation rather than the Nernst equation to determine a membrane potential if
a. the valance of the ions was +2 or -2 or more.
b. the membrane was part of a living cell.
c. the temperature differs from 37°C.
d. the membrane can show action potentials.
e. more than one ion is crossing the membrane.
12. The difference between repolarization and hyperpolarization of a cell membrane is
a. repolarization is a positive change in voltage while hyperpolarization is a negative change.
b. repolarization is a negative change in voltage while hyperpolarization is a positive change.
c. repolarization is a change back towards resting voltage while hyperpolarization is a negative change from resting voltage.
d. repolarization is a negative change from resting voltage while hyperpolarization is a change back towards resting voltage.
e. These terms are synonymous.
13. The drop in voltage following the peak of an action potential is driven by
a. the opening of sodium channels.
b. the closing of sodium channels.
c. the opening of potassium channels.
d. the closing of potassium channels.
e. Two of the above. (b and c)
14. Axons with better cable properties have faster propagation of action potentials because
a. the depolarization caused by each action potential is conducted further along the axon before dropping below threshold.
b. each action potential shows a stronger depolarization.
c. each action potential is shorter in duration.
d. each action potential is longer in duration.
e. action potentials are more frequent.
15. The neurotransmitter released from the pre-synaptic axon reaches the receptor proteins in the post-synaptic neurons by
a. permeation.
b. diffusion.
c. active transport.
d. gap junctions.
e. the direct contact between the two neurons.
16. A post-synaptic ligand-gated ion channel that allows more chloride ions to flow into the cell would cause what effect on post-synaptic potential?
a. Excitation (positive change).
b. Inhibition (negative change).
c. No change.
d. It is impossible to know.
e. Blue.
17. Which of the following is not a catecholamine?
a. Epinephrine.
b. Norepinephrine.
c. Serotonin.
d. Dopamine.
e. All of these are catecholamines.
18. A sensory neuron that shows changes in the frequency of action potentials it produces while exposed to a constant stimulus is said to be undergoing
a. adaptation.
b. adjustment.
c. amplification.
d. interoception.
e. lateral inhibition.
19. Range fractionation provides for which of the following in the sensory system?
a. An increased signal-to-noise ratio.
b. A strong response to changing stimuli.
c. Strong amplification of weak stimuli.
d. Transduction of a wider limit of stimuli than would be possible with a single receptor.
e. Reception by a single neuron over a wide sensory field.
20. The ability of the semi-circular canals to detect rotational movement depends in part on
a. the presence of otoliths.
b. the inertia of the fluid filling the canals.
c. the activation of baroreceptors.
d. Two of the above.
e. All of the above.
21. A deficiency of phosphodiesterase in a vertebrate rod cell would probably cause
a. constant hyperpolarization of the photoreceptor.
b. constant depolarization of the photoreceptor.
c. rapid alternation between depolarization and hyperpolarization in the photoreceptors.
d. inactivation of rhodopsin.
e. inactivation of transducin.
22. A chemical messenger which targets the cell that released it is known as a(n)
a. autocrine agent.
b. exocrine agent.
c. hormone.
d. paracrine agent.
e. A chemical messenger would never affect the cell that released it.
23. Steroid hormones have their effects on cells by
a. opening or closing ligand-gated ion channels.
b. activating G-protein pathways.
c. activating membrane-bound enzyme complexes.
d. altering the transcription rate for certain gene products.
e. altering the rate of protein degredation.
24. A
person whose anterior pituitary was not making could not make
adrenocorticotropic hormone would probably have
a. lower than normal levels of corticotropin releasing hormone (CRH) and cortisol.
b. higher than normal levels of CRH and cortisol.
c. higher than normal levels of CRH and lower than normal levels of cortisol.
d. normal levels of CRH and higher than normal levels of cortisol.
e. normal levels of CRH and lower than normal levels of cortisol.
25. A lack of dietary iodine makes it impossible to produce
a. thyrotropin releasing hormone.
b. thyroid stimulating hormone.
c. thyroxine.
d. triiodothyronine.
e. Two of the above. (c and d)
Short answer: Write a concise answer to each of the following questions. Your answers should fit in the spaces provided and should address only the question asked. Diagrams must be accompanied by written explanations. Each question is worth 6 points.
26. As part of an exobiological expedition, you are conducting a physiological study on the waffle-backed silt-sucker. Specifically, you are investigating the regulation of the compound halitocin in the blood of the silt-sucker. Here is what you know:
a. The Barcroft organ of the animal releases increasing amounts of halitocin from its storage vesicles into the blood stream as the level of the compound dyspepsine in the blood increases.
b. The Guitierrez organ releases decreasing amounts of emetisol as levels of halitocin in the blood increase.
c. The Malik organ releases increasing amounts of dyspepsine as the level of the emetisol in the blood increases.
Given this information, indicate which function in a standard negative feedback loop each of the following is most likely to serve:
Barcroft organ – Effector
Guitierrez organ – Sensor
Malik organ – Integrating center (possibly with setpoint)
Dyspepsine – Efferent pathway
Emetisol – Afferent pathway
27. Describe
the activity of the two gates in the voltage-gated sodium channels of a
neuronal axon. You should include the trigger for each event, the relative timing
of these events and the consequences for sodium ion flow.
There are two gates in these sodium channels – a fast activation gate and a
slow inactivation gate. Initially the activation gate is closed and the
inactivation open. Membrane voltage rising above threshold causes both gates
to switch states, but the activation gate opens faster than the inactivation
gate closes, so the channel is briefly open, allowing ion low before the
inactivation can fully close. Once channel is closed again it will stay closed
until membrane voltage drops back below threshold, when the activation gate
re-closes and the inactivation re-opens. Again, the activation gate is faster,
so at least one gate is closed throughout this period and no ion flow occurs.
28.
Consider a neural synapse with two presynaptic neurons, one of which
produces excitatory post-synaptic potentials and the other of which produces
inhibitory post-synaptic potentials. Describe the types of summation that
might occur, and how each might affect the initiation of action potentials in
the post-synaptic neuron.
With two pre-synaptic neurons, both temporal and spatial summation could
occur. The excitatory neuron might be able to trigger an AP in the
post-synaptic neuron with a single epsp, but if not then a series of
sufficiently rapid epsp’s could result in temporal summation of the excitatory
effects to the threshold voltage. Temporal summation of the ipsp’s could also
occur, which would hyperpolarize the membrane more than a single ipsp would.
Spatial summation would result in the epsp’s and ipsp’s canceling each other to
some degree. A series of epsp’s that would have reached threshold could be
prevented from triggering an AP if one or more ipsp’s occurred at the same
time.
29. Provide a brief description of the mechanisms that result in membrane depolarization for each of the following four types of taste receptors:
Salt – The sodium ions of the salt enter the cells directly through sodium channels, depolarizing the membrane.
Sweet – Sweet molecules primarily activate G-protein systems that ultimately close K+ channels, resulting in depolarization.
Sour – In sour receptors, H+ ions change Vm by blocking K+ channels.
Bitter – Bitter compounds block K+ channels directly or activate receptors in a G-protein complex. [The G-protein pathways can work in a number of ways to trigger neurotransmitter release.]
30. Describe
the events in the scala media of the mammalian cochlea during the transduction
of sound. A diagram may be used but is not necessary.
The scala media is physically moved as pressure changes in the scala
vestibuli – down towards the scala tympani when pressure increases and up
towards the vestibuli as the pressure decreases. The mechanical structure of
the media is such that the tectorial membrane, which is connected to the top of
the stereo cilia of the hair cells, slides horizontally relative to the organ
of Corti, which supports the base of the hair cells. This means that the cilia
are alternately bent first to one side then the other, which changes the
membrane potential of the hair cells. This in turn changes the amount of
neurotransmitter released. The more neurotransmitter released by each hair
cell, the more frequent the action potentials in the afferent neuron that
synapses with it.
31. Complete the following table for the hypothalamic-pituitary system with the appropriate hormones, target organs and effects. (Note that this is not a complete table.) Be sure to provide the full name of each hormone, not the abbreviation.
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Target Organ or Tissue |
| Gonadotropin releasing hormone |
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Follicle stimulating hormone | |
Gonads → Sex hormone release, gamete development |
| Luteinizing hormone |  |
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| Prolactin releasing hormone | |
Prolactin | |
Breasts → Breast development, milk production |
| Growth hormone releasing hormone | |
Growth hormone |
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Body tissues → Cell division & hypertrophy, protein synthesis |
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Liver → IGF-I release |