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BIOL
260 Human Physiology, Fall 2009, Prof. Stark
First
Hourly Exam, September 25, Short Answer
1. A model for the exponential decrement of voltage along the length of the axon was shown in the first lecture. I said ³along the length of the axoplasm, there is resistanceŠout in the extracellular space there is resistance but not much.² Why isn¹t there much?
Because there is not a confined space
2. ³The action potential depolarizes the axon ahead of it to the threshold (for the action potential, and how far this spreads is described by an exponential drop-off.² What does myelin do to this distance?
Increases it
3. The drugs that some athletes abuse are sometimes called anabolic steroids. What does the word ³anabolic² imply?
Anabolic refers to build-up
4. ³The adrenal is two glandsŠThe adrenal medulla releases adrenaline.² The other partŠ Answer either (1) what is it called? Or (2) what does it release?
1 adrenal cortex 2 cortisol (and others)
5. Regarding the regulation of blood flow to your periphery, for instance your hands, how would this contribute to temperature regulation?
Radiate more heat if vasodilation
6. Goiter. Answer either (1) This is caused by too MUCH of what hormone? Or (2) Why is there too much of this hormone?
1 TSH 2 insufficient T3 & T4 -> insufficient negative feedback
7. What is different about the circulatory system of the hypothalamus - anterior pituitary than most other parts of the body?
Portal system
8. ³11-cis retinal (a bent form of the aldehyde of vitamin A) is the chromophore of rhodopsin.² In terms of the molecule¹s interaction with visible light, what does this mean.
Gives the protein its property of absorbing visible light
9. ³The two half leaflets of the membrane, as seen in freeze-fracture, are called P- and E-faces.² Answer either (1) why P and E? or (2) describe why these two halves are distinct from each other.
1 protoplasmic (on the cell side) exoplasmic (the external side), 2 turns out that the proteins are usually seen on the P-face
10. ³Diacyl glycerol.² Explain how this name, by itself, would tell you what would have had to happen to a membrane phospholipid to make diacyl glycerol.
2 farry acids (acyl groups) attached to a glycerol means that the polar head group had been chopped off
11. Tell me how autoradiography of a TLC (thin layer chromatography) plate can help you identify the numerous phospholipids of the cell membrane.
A TLC plate separates lipids, labeling with radioactive phosphate allows exposure of an audorad
12. ³IP3 is a ligand forŠ² answer either (1) What kind of molecule? Or (2) Where is the molecule (that it is a ligand for)?
1 channel for calcium ion 2 on a smooth ER that sequesters calcium
13. The Voltage across the membrane is –RT/F times a number. R is in units of Joules/(mole x degreeKelvin) and F is in units of Coulombs/mole. Of course, we could use the term ³Volts² for membrane Voltage. Alternatively use the information provided above to state what other units could be used for membrane Voltage.
Joules per Coulomb
14. From the 1930¹s to the 1950¹s, why did Cole and Curtis, also Hodgkin and Huxley, choose the squid instead of the frog to characterize action potential conductances?
The axon is big
15. I stimulate an axon with a ³square wave² (an immediate step upward of voltage). Does the axon act as a high-pass filter or a low-pass filter? Justify.
Slow upsweep implies low pass (high cutoff)
16. ³The sum of potentials, batteries and current flowing through resistors, around a loop of a circuit is zero. Also the sum of currents flowing into the junction in a circuit is zero.² Whose laws are these?
Kirchoff¹s
17. In an equivalent circuit of the Goldman equation, there are batteries and resistors. What particular feature do these (in the Goldman model) resistors have?
They are variable resistors (potentiometers)
18. What was concluded about the properties of the axon during an action potential on the basis of Cole and Curtis¹s AC Wheatstone bridge experiment?
Resistance goes down
19. Structurally, how are Schwann cells and oligodendrocytes different?
Schwann myelinate one axon, og. Do a few (hence oligo-)
20. Molecularly. What does it look like when inactivation of a channel occurs?
A stopper plugs up the channel
21. In what way was multiple sclerosis modeled as an autoimmune disease?
A basic protein in myelin, usually sequestered from immune surveillance induces immune attack on myelin
22. Tetrodotoxin (from puffer fish) would kill you by what mechanism?
Blocks sodium channels and hence the action potential
23. Sherrington said that the spinal motor neuron was the final common pathway of the nervous system. How does this relate to excitation and inhibition in the spinal motor neuron vs. the muscle cell?
b/c there is only excitation on the end plate, the neuron is the last chance to integrate IPSPs and EPSPs
24. ³Botulinum and tetanus toxins cleave synaptobrevin.² In terms of nerve function, why would they kill you?
Prevent vesicle release
25. What would be the cause of death if you were poisoned by malathion, an inhibitor of acetylcholinesterase?
Heart would stop
26. At one time, the precursor of norepinephrine was considered to be just that, a step in the pathway to norepinephrine synthesis. Now it is considered an important transmitter. Answer either (1) What is it called? (2) Where does it come from in the brain? Or (3) Its deficiency is the cause of what disorder?
1 dopamine 2 substantia nigra 3 Parkinsons
27. ³The alpha subunit stimulates adenylate cyclase.² Answer either (1)The alpha subunit of what heterotrimeric molecule? (2) What stimulated this heterotrimeric molecule? Or (3) What does the adenylate cyclase make when it is stimulated?
1 G protein 2 G protein coupled receopto 3 cAMP
28. Caffeine: Answer either (1) What does it do chemically? Or (2) What neurotransmitter¹s action is potentiated by its action?
1 block the PDE that inactivates cAMP 2 NE
29. Why does the inner layer of the blood vessel (the endothelium) come up in an explanation of erection?
Endothelial NOS makes NO
30. ³The autonomic nervous system is a motor system.² Thus the CNS (central nervous system) location of the cell body of origin (not the ganglion) is in the gray matter of the spinal cord and also (finish this sentence).
The brain
31. In the somatic motor system, connecting to striated muscle, we refer to the ³neuromuscular junction.² For the autonomic nervous system, we are more non-committal with the term ³neuroeffector junction² instead. Why?
b/c it could also be glands
32. For nicotine, answer either (1) Where (anatomically) does it affect the autonomic nervous system? Or (2) What neurotransmitter is involved?
1 the ganglia 2 acetylcholine
33. Via beta-1-adrenergic receptors, the sympathetic nervous system increases the contractility of heart muscle and (in what other way does it affect the heart?).
increase rTE
34. Why would people have used a muscarinic receptor blocker as a cosmetic?
Dilated pupils are appealing
35. Give an explanation, from developmental biology, of why there are many nuclei in a skeletal muscle fiber.
36. Why would a body builder want to exercise before a show?
Hyperemia would make muscles look larger
37. If we were to compare fully extended vs. contracted striated muscle in histology, how, if at all, would the I-band look different?
Shorter in contracted
38. In muscle contraction, which needs to bind to muscle protein first, calcium ions or ATP? Justify your answer.
Calcium. ATP cannot replace ADP until myosin can see the binding sites on actin
39. ³The problem is that the action potential is on the muscle cell membrane quite some distance from most of the sarcomeres.² How is that problem solved?
t-tubules get action potential around
40. ³Action potentials are all or none. In contrast, muscle twitches² (finish this sentence and mention what happens when there are a whole lot of twitches).
Twitches can have summation and if enough twitches add, there is tetanus
41. ³The turkey leg has dark meat, and the reason it looks dark is² finish this sentence.
Hemoglobin, myoglobin, cytochromes
42. In addition to muscle glycogen and blood glucose, what material from where supplies calories for muscle?
Fat in muscle, fatty acids in blood
43. Describe how the blood stream succeeds in delivering oxygen to muscle by describing how that looks on the oxyhemoglobin dissociation curve.
Since mgb is to the left of hgb, hgb offloads oxygen to mgb
44. In what way does the source of calcium ions differ between smooth muscle and striated muscle?
From extracellular smooth, SR striated
45. When activated, what effect does myosin light chain kinase (MLCK) have on contraction of smooth muscle.
Phosphorylates myosin allowing cross bridges and myson and actin to slide.
46. What does the dehydration synthesis have to do with the comparison with monosaccharides and glycogen?
Puts units together in macromolecule
47. I rationalized that you might call a releasing hormone from the hypothalamus to the pituitary (through the portal system) a ³peptide.² Why peptide rather than protein?
Very short
48. Urea, answer one: (1) Referring to energy metabolism, why do we make this? Or (2) What are the precursors?
1 nitrogenous waste when a.a.used as calories 2 NH3 (ammonia) and carbon dioxide
49. ³Fatty acids are chopped down two carbons at a time.² Where, specifically, does this 2-carbon segment go to generate ATP.
Right to acetyl co-A in Krebs
50. When the insulin receptor dimerizes upon activation by insulin, answer either (1) What is the result of this enzyme¹s activity? (2) What molecule does this enzyme act on? Or (3) Where did the phosphate come from?
1 phosphate gets added to tyrosine 2 the insulin receptor itself 3 ATP
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