Download figures from Lin et al.

BBio 351: Principles of Anatomy & Physiology I
Exam 3 (mostly neuro/sensory)
Fall 2015
Name: ____Dr. C___________________
Grading: all point deductions were made from a maximum of 105 points; everyone was then
given an additional 5-point bonus. Example for 30 points deducted: 105 – 30 = 75. 75 + 5 = 80.
Part A: short answer
1. Consider the paper “Parallel neural pathways mediate CO2 avoidance responses in
Drosophila” by H.-H. Lin et al. (Science 340: 1338-1341, 2013; see handout for figures).
a. In this study, what are projection neurons (PNs)? [3 pts.]
 Projection neurons convey sensory information from the antennal lobes to the
deeper parts of the brain (lateral horns, superior dorsofrontal protocerebrum, etc.)
b. What do PNv-3’s do in Drosophila, according to this study? [3 pts.]
 PNv-3’s suppress the PNv-1-mediated avoidance of low CO2 (0.5%).
c. Explain how specific experimental measurements made by Lin et al. led to the
conclusion in part B (the previous question). Be as specific and as detailed as possible.
[4 pts.]
 Figure 4E shows that when PNv-3’s are activated (by blue-light activation of ChR2
channels, in this case), avoidance of 0.5% CO2 is suppressed.
d. What do PNv-2’s do in Drosophila, according to this study? [3 pts.]
 PNv-2’s mediate avoidance of high CO2 (2%).
e. Explain how specific experimental measurements made by Lin et al. led to the
conclusion in part D (the previous question). Be as specific and as detailed as possible.
[4 pts.]
 Cite either or both of the following:
o Figure 2C: turning OFF the PNv-2’s (via the shits1 mutation) reduces the
behavior of avoiding 2% CO2.
o Figure 3B: turning ON the PNv-1’s (via the ChR2 ion channels) increases
avoidance behavior. This, combined with earlier data on CO2 sensitivity,
indicates that these neurons mediate avoidance of CO2.
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BBio 351: Principles of Anatomy & Physiology I
Fall 2015
2. Fill in the top graph of the panel below with the approximate progression of an action
potential that begins at a time of 1 millisecond. Then graph the approximate values of P Na (the
term from the Goldman-Hodgkin-Katz equation) and extracellular [Na+] during an action
potential over this same time period. [3 pts. per panel = 9 pts.]
Top panel:
 1 pt. for starting at a
baseline around -70 mV
 1 pt for peaking at about
+30/40 mV
 1 pt. for returning to a
baseline around -70 mV
Middle panel:
 1 pt. for starting low (-0.5
for starting at 0)
 1 pt. for going to high
during the rising phase of
the action potential
 1 pt. for returning to low
at the peak of the action
potential or shortly
thereafter
Bottom panel:
 1 pt. for concentration
being ≥100 mM
 2 pts. for concentration
staying constant
3. Synapses between motor neurons and muscle cells are similar to synapses between two
neurons; however, no temporal or spatial summation is needed to make the muscle cell “fire”
(depolarize and contract). Make an educated guess as to how the cellular/molecular anatomy
of these synapses eliminates the usual need for summation. [3 pts.]
 Multiple answers are possible. The key is to offer some rationale as to why the muscle
cell’s “threshold” is always reached. For example, lots of neurotransmitter is released,
so the muscle cell always depolarizes fully.
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BBio 351: Principles of Anatomy & Physiology I
Fall 2015
4. At right are graphs of the
same photoreceptor’s response
to two different flashes of light,
both starting at time = 1
millisecond. Which flash was
bigger? Explain how you can
tell OR why you can’t tell.
[4 pts.]
 Photo receptors
hyperpolarize in
response to photons [2
pts.]
 Since the magnitude of
hyperpolarization was
greater in B, more light
was received [2 pts.]
5. For each of the two histology images below (taken from medcell.med.yale.edu and
ntp.niehs.nih.gov), say what kind of tissue you think it is and why you think that. Your choices
are: epididymis, ovary, pancreas, penis, spinal cord, thyroid gland, uterus. [3 pts. each = 6 pts.]
[For each: 1 pt. for ID, 2 pts. for explanation]
LEFT: thyroid gland. Large cell-free colloid spaces surrounded by follicular cells with blue nuclei.
RIGHT: pancreas. Little islands of lightly stained tissue (endocrine) amidst a sea of mostly
darker stained tissue (exocrine).
6. Evaluate the accuracy of the following statement: “The brain distinguishes among different
pitches (frequencies) of sounds based on which hair cells are stimulated by those sounds.
Specifically, the longer, thicker hair cells respond best to low frequencies, while the shorter,
thinner ones respond best to high frequencies.” [4 pts.]
The problem with this statement is that the hair cells are all similar in morphology; it is the
basilar membrane that varies in thickness, and that has different sections responding to
different frequencies. The first sentence of the statement is correct, though; different hair cells
do correspond to different frequencies because they are connected to different sections of the
basilar membrane.
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BBio 351: Principles of Anatomy & Physiology I
7. Label the following structures of
on the diagram of a ventral view of
a sheep brain (taken from E.N.
Marieb et al., Human Anatomy &
Physiology Laboratory Manual). [2
pts. per structure = 12 points]






Cranial nerve II
Cranial nerve VIII
Medulla
Olfactory bulb
Optic chiasm
Pons
Fall 2015
Olfactory
bulb
Cranial nerve II
Optic chiasm
Optic chiasm
Pons
Cranial nerve VIII
Medulla
8. What is it like to have a conversation with a patient with damage to Wernicke’s area? What
does this indicate about the function of Wernicke’s area? [5 pts.]
 The patient will babble randomly and nonsensically rather than responding to the
questions asked. [2.5 pts.]
 The function of Wernicke’s area is comprehension of language. [2.5 pts.]
9. Explain the molecular/cellular basis by which lidocaine causes anesthesia. Which
components of which cells are affected? Which process(es) is/are altered or prevented? [5
pts.]
 Channels blocked are Na+ channels.
 Channels blocked are voltage-gated/in axons.
 Action potentials do not occur in these neurons.
 Sensory neurons are blocked, so sensory information doesn’t reach the brain.
10. If you artificially inject current midway between the axon hillock and axon terminus, can
you get an action potential to spread toward the axon hillock? Why or why not? [4 pts.]
 Yes you can! If initial injection is in the middle of the axon, “upstream” Na+ channels are
not in their refractory period and can open, spreading the signal back toward the axon
hillock.
11. An alien lands on Earth and is found to be exactly like humans in every way. The alien’s
neurons have a Na+ equilibrium potential (ENa) of +55 mV, according to the Nernst equation.
What is the significance of this value? That is, what happens (or doesn’t happen) at this specific
value? [4 pts.]
 Either (or both) of the following:
o At this membrane potential, there is no net flow of the ion into or out of the cell.
o At this membrane potential, the electrical gradient is exactly equal and opposite
to the chemical gradient, so that the two cancel each other out.
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BBio 351: Principles of Anatomy & Physiology I
Fall 2015
Part B: multiple choice (please choose the single best answer; 2 pts. apiece)
12. In the diagram at right (from
http://kentsimmons.uwinnipeg.ca;
original source unknown) which
labeled structure is the white matter
of the spinal cord?
a. 083-YES b. 084 c. 085 d. 086
13. The white matter of the spinal
cord mostly contains
a. Axons-YES
b. Cell bodies
c. Dendrites
d. Non-neuronal receptor cells
e. Synapses
14. Which of the following helps explain why edges are accentuated by lateral inhibition?
a. Edges are detected by phasic receptors, which are more sensitive than tonic ones.
b. Lateral receptors have higher receptor densities (smaller receptive fields) than medial ones.
c. Only the edges cause IPSPs mediated by lateral inhibition.
d. The stronger the stimulus sensed by a given receptor/sensory neuron, the more that it will
inhibit adjacent receptors/sensory neurons.-YES
15. In mammals, depth perception and sound localization both require
a. Auditory receptors
b. Cranial nerve II
c. Convergence and comparison of inputs from both sides of the body-YES
d. The frontal cortex
e. All of the above
16. Which of the following accurately describes one of Ca2+’s roles in photoreceptors?
a. enters photoreceptors via ion channels; inhibits cGMP production by guanylate cyclase-YES
b. enters photoreceptors via ion channels; stimulates cGMP production by guanylate cyclase
c. exits photoreceptors via ion channels, thus depolarizing the cell membrane
d. exits photoreceptors via ion channels, taking photons with it and thus promoting adaptation
17. Which of the following is a way in which hair cells differ from most sensory receptors?
a. Extracellular [K+] is high, so K+ is near equilibrium, and there is little flow of K+ in or out.
b. Extracellular [K+] is high, so there is not much of a chemical gradient, and K+ follows the
electrical gradient inward.-YES
c. Extracellular [K+] is high, so there is not much of a chemical gradient, and K+ follows the
electrical gradient outward.
d. Extracellular [K+] is low, so K+ follows the chemical gradient outward.
e. The membrane potential is highly positive at rest, pushing K+ outward.
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BBio 351: Principles of Anatomy & Physiology I
Fall 2015
18. The main ion channels responsible for changes in the membrane potential of hair cells are
a. ligand-gated b. mechanically gated-YES c. voltage-gated d. bill-gated e. not gated
19. How do G proteins contribute to the function of photoreceptors?
a. G proteins are stimulated by rhodopsin to activate a phosphodiesterase, which consumes
cGMP.-YES
b. G proteins directly receive photons and change their shape in response to the photons.
c. G proteins sequester calcium, thus promoting adaptation.
d. The channel through which “dark current” Na+ ions pass is a G protein.
e. All of the above
20. Binding of epinephrine to _____________ on/in _________ causes vasodilation.
a. alpha receptors; skeletal muscle cells
b. alpha receptors; cardiac muscle cells
c. beta-2 receptors; smooth muscle cells-YES
d. hormones; adrenal medulla cells
e. transcription factors; smooth muscle cells
21. The physical abnormality of the woman at right
(picture by Martin Finborud via Wikipedia) is due to
excessive production of a hormone by the
a. anterior pituitary-YES
b. hypothalamus
c. thalamus
d. thymus
e. thyroid gland
22. GnRH production by the hypothalamus in mammals
may be influenced by which factors?
a. estrogen
b. melatonin
c. both estrogen and melatonin-YES
d. neither estrogen nor melatonin
23. Which of the following IS true of sensory receptors that are neurons, but is NOT true of
sensory receptors that are NOT neurons?
a. Only the neurons change their membrane potential in response to stimuli.
b. Only the neurons fire action potentials.-YES
c. Only the neurons have ion channels.
d. Only the neurons release neurotransmitter.
e. All of the above.
24. The 12 cranial nerves are collectively included in the ______ nervous system(s).
a. afferent b. efferent c. afferent AND efferent-YES d. [neither afferent nor efferent]
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BBio 351: Principles of Anatomy & Physiology I
Fall 2015
25. How can you distinguish among odorants such as those at right (image
from NobelPrize.org)?
a. They all bind to the same olfactory receptor protein, but taste buds
contribute additional input that helps you distinguish them.
b. They all bind to the same olfactory receptor protein, but with different
affinities (strengths).
c. Each odorant binds to one unique receptor protein expressed by a particular
receptor cell.
d. Each odorant binds to multiple receptor proteins on different receptor cells,
and the brain identifies each odorant based on the combinations of receptors
that are activated.-YES
e. Each odorant is endocytosed by olfactory receptor cells and used as a
neurotransmitter, which then passes into the brain, which recognizes it.
26. The medulla and pons directly receive which of the following types of sensory information?
a. auditory-YES b. olfactory c. visual d. B & C e. A, B, & C
27. The following arrangement constitutes a circuit that is capable of “remembering” a previous
stimulus:
a. a linear arrangement of neurons (1 pre-synaptic neuron synapses with 1 post-synaptic
neuron)
b. a neuron that synapses back onto itself, thus stimulating itself-YES
c. one pre-synaptic neuron branching to form synapses with several post-synaptic neurons
d. a post-synaptic neuron that receives all of its inputs at the cell body, rather than the
dendrites
e. several pre-synaptic neurons converging onto one post-synaptic neuron
Below: figures from Lin et al., Science 2013
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BBio 351: Principles of Anatomy & Physiology I
Fall 2015
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