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Explain the structural differences of the contractile units inskeletal, cardiac, and smooth muscle. Why would calcium channelblocking hypertension drug have an effect on blood vessels andcardiac muscle but not affect coordination or the ability tooperate skeletal muscle tasks?

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Casey Durgan
Casey DurganLv2
28 Sep 2019

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1. What factors determine the contraction of skeletal muscle? How is skeletal muscle contraction and relaxation different from cardiac muscle? How smooth muscle can regulate blood flow and perfusion?

2. Why is the cardiac action potential propagated more slowly in an AV node cell then in an atrial or ventricular myocyte? How can be AV conduction affected by hypokalemia? How hypokalemia can affect cardiac rhythm?

3. What physiological factors influence capillary blood flow? How can this be changed during stress conditions? How capillary blood flow changes during exercise?

4. What are the major compensatory responses to blood loss? List the most important hormones involved. How vasopressin can regulate blood flow?

5. An individual has an episode of gastroenteritis with vomiting and diarrhea. How will this affect his intracellular and extracellular fluid compartments volume and osmolality? What acid-base abnormality will he develop? What treatment regarding water balance would be necessary?

1. Be able to define the following terms: releasing hormone,inhibiting hornone, trooic hormone, nontropic hormones,neurosecretory cells.

2. What are hormones?

3. What are two specific differences between the endocrine andnervous systems?

4. What are the four different types of cell signaling?

5. What are the three types of hormonal control pathways? Givean example of each.

6. What is local regulator?

7. What type of feedback is a common feature of pathways thatcontrol homeostasis?

8. What are the three major classes of molecules that functionas hormones? Which are water-souble and which are lipid-souble?

9. Signaling by a hormone involves three key events. What arethey?

10. What is the correlation between solubility of a hormone andthe location of its receptors?

11. In addition to receptor location, water-soluble andlipid-soluble hormones also exhibit additional differences in theirresponse pathways. What are these differences?

12. What is signal transduction pathway?

13. Why can the same hormone have different effects on differentbody tissues?

14. Liver cells and the blood vessels of skeletal muscle cellshave identical surface receptors for epinephrine, yet the responeof these two cells types is dramatically different. Explain howthis is possible.

15. In the "fight or fight response" the release of epinephrinefrom the adrenal medulla cause skeletal muscle blood vessels todilate while simultaneously constricting blood vessels of theintestine. Explain how this is possible.

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A new class of agents has been developed which alters the conductance of ion channels. Unfortunately, it is not clear what ion channels are being affected or what the effect is on conductance. To investigate this, you examine an isolated vertebrate nerve- skeletal muscle preparation which allows you to stimulate the nerve and examine the resulting muscle contraction. Consider each set of results and reply to the questions.

a) You stimulate the nerve in the presence of Agent X and the muscle contraction is stronger and more prolonged than when the agent is not present. There is no change in the muscle when exposed to Agent X in the absence of nerve stimulation.

i) What channels might be affected and how?

ii) Design experiments which could differentiate between the options you have listed.

b) When you add Agent Y to the fluid bath in which the nerve-muscle preparation is being maintained, the muscle contracts spontaneously without you having to stimulate the nerve. When atropine is applied to the fluid bath, however, the muscle does not react to the presence of Agent Y.

i) What is/are the most likely targets and how are they being altered by Agent Y?

ii) Design a set of experiments to determine the actual target and effect of Agent Y

c) Agent Z also causes spontaneous contraction of the muscle. However, atropine does not block this effect. What is/are the most likely target(s) and effect(s) of Agent Z?

d) Agent Q is known to increase calcium conductances.

i) What results would you expect to see when Agent Q is added to your preparation?

ii) Agent Q turns out to be ionized under normal physiological pH, such as found in your bathing fluid. Does this help determine the target/mode of action of Agent Q? If so, how?

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