Exam 3 Posted Answers

Exam 3 Posted Answers - BISC 220, Spring 2008, Exam 3...

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BISC 220, Spring 2008, Exam 3 Answers 1. Contractions of the uterus during labor are stimulated by the pituitary hormone oxytocin. The secretion of oxytocin is stimulated by contractions of the uterus. Which one of the following best describes the interaction between the pituitary gland and the uterus in this case? (c) a. The uterus produces the response in a negative feedback loop. b. The pituitary is the control center in a negative feedback loop. c. The pituitary and uterus are interacting in a positive feedback loop. d. The interaction between the pituitary and the uterus illustrates how negative feedback maintains homeostasis. 2. Blood pressure in the left ventricle is lower than blood pressure in the pulmonary vein… (c) a. during ventricular systole. b. when the semilunar valve between the left ventricle and aorta is open. c. when the ventricles are relaxed. d. never, i.e., pressure in the left ventricle is never lower than pressure in the pulmonary vein. 3. Which one of the following statements about cardiac output is correct? (c) a. Cardiac output is normally higher for the left ventricle. b. Cardiac output is normally higher for the right ventricle. c. Cardiac output of both ventricles is normally equal. d. Cardiac output equals stroke volume divided by heart rate. 4. Is the sum of blood flow in both pulmonary arteries normally less than, the same as, or more than blood flow in the aorta? Explain your answer. ANS: The sum of blood flow in both pulmonary arteries is normally the same as blood flow in the aorta. The right and left sides of the heart are in series. So, blood pumped by the right side into the pulmonary arteries forms the input to the left side, which pumps blood into the aorta. The output of the two sides of the heart must normally be exactly equal, or blood will back up and cause abnormally high pressure in either the pulmonary or systemic circulation. 5. Which one of the following statements about veins is true? (c) a. Veins always carry blood partially depleted in oxygen. b. Blood pressure in veins is always slightly higher than blood pressure in venules. c. Veins always transport blood toward the heart. d. Because veins have thinner walls than arteries, exchange of respiratory gases can occur across the walls of veins but not arteries. 6. The application of constant pressure to an edematous part of the body is an effective way of reducing the swelling. Which one of the following best explains why this works? (a) a. The sum of the pressures forcing fluid into capillaries exceeds the pressure forcing fluid out of capillaries. b. The applied pressure causes local release of histamine, which increases tissue drainage. Page 1 of 6
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c. The fluid is sufficiently compressible that applying pressure reduces its volume directly. d. The applied pressure opens precapillary sphincters.
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Exam 3 Posted Answers - BISC 220, Spring 2008, Exam 3...

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