prob_set7a_solns - Solns prob set #7a Page 1 of 4 Solutions...

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Solutions to Problem Set #7 for BEFORE the 2nd midterm exam 4. When cardiac muscle fibers are mildly stretched, they contract with greater vigor and more blood is ejected from the heart. Cardiac muscle fibers become mildly stretched when venous return increases, so increased venous return leads to more vigorous contraction and increased cardiac output. The heart thus modifies its contractile strength to compensate if extra blood returns from the venous side of the circulation. (Point of interest: the connective tissue in the heart makes the heart very difficult to stretch beyond a certain point, so a length-tension diagram of the whole heart will not show the tension dropping all the way back to zero for long stretch, as you see in the length-tension curve for skeletal muscle. It is impossible to stretch the living heart that much.) If venous return drops, the cardiac muscle fibers are less stretched and they contract with less vigor. Therefore, if less blood returns to the heart, contraction of the heart is less vigorous and a lower volume of blood is pumped out of the ventricles. 8. See the cardiac cycle diagram in your course outline or see Figure 14-26 on p. 499 of your text. 9. a. Fluid transfer = k[(P cap - P int )) - (¼ cap - ¼ int )] From the graph, at the arterial end of the capillary, P cap = 30 mmHg. P int is very close to 0 under all normal circumstances. Therefore, the net fluid transfer across the arterial end of the capillary = k[30 - 0 - 25 + 15] = 20 x k. A
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This note was uploaded on 10/16/2011 for the course BIPN 100 taught by Professor French during the Fall '07 term at UCSD.

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prob_set7a_solns - Solns prob set #7a Page 1 of 4 Solutions...

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