BISC220Lg Exam 3 Practice

BISC220Lg Exam 3 Practice - BISC220Lg Exam 3 Practice 1....

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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? 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. Positive feedback circuits trigger mechanisms that amplify rather than diminish the stimulus. Negative feedback is a response that reduces or counteracts the stimulus to maintain homeostasis. 2. Blood pressure in the left ventricle is lower than blood pressure in the pulmonary vein… 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. The answer is C. Blood flows down pressure gradients, from high to low pressure. The blood from the pulmonary vein flows into the left atrium and then into the left ventricle. In order for this direction of blood flow to occur, the left ventricle must have a lower pressure than the left atrium which must have a lower pressure than the pulmonary vein as well. Therefore the answer must be C. The answer cannot be. ..because. ..: A - during ventricle systole the ventricles are contracting and have a very high pressure B - if the semilunar valve between the left ventricle and the aorta is open that means that the pressure in the ventricle exceeded the pressure in the aorta opening the valve and allowing blood to flow down the pressure gradient. D - if the pressure in the left ventricle was always higher than the pressure in the pulmonary vein than blood would not flow into the ventricle but from the ventricle to the vein which we know does not happen. 3. Which one of the following statements about cardiac output is correct? 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. The pressures are different, but the outputs are the same. 4. Which one of the following statements about veins is true? a. Veins always carry blood partially depleted in oxygen. b.
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This note was uploaded on 04/21/2009 for the course BISC 220L taught by Professor Herrera,mcclure during the Spring '07 term at USC.

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BISC220Lg Exam 3 Practice - BISC220Lg Exam 3 Practice 1....

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