1 BISC 307, Exam 3 Answers Spring 2015 1. Which one of the following hormones is incorrectly paired with its action? (c) a. GnRH  controls release of FSH and LH b. Luteinizing hormone  stimulates ovulation c. Progesterone  stimulates development of ovarian follicles d. Chorionic gonadotropin  maintains secretions from corpus luteum e. Estrogen  development of primary and secondary female sex characteristics 2. Which one of the following statements is false? (d) a. Granulosa cells surround the ovulated oocyte. b. Continuous release of GnRH would decrease release of FSH and LH. c. Progesterone levels are higher in the second half of the ovarian cycle. d. The degeneration of Müllerian ducts in male fetuses is a direct effect of testosterone. e. If a man with autoimmune disease developed antibodies that blocked FSH receptors, circulating levels of inhibin would be lower than normal. 3. Indicate whether each of the following statements is true or false by writing the word “True” or “False” in the blank. Do not write T or F. ANS: a-T, b-F, c-T, d-F ____________ a. Frequent soaking in hot tubs or heated Jacuzzis can reduce male fertility. ____________ b. Estrogens control the development of the reproductive organs in the female fetus. ____________ c. FSH stimulates granulosa cells directly, while LH stimulates granulosa cells indirectly. ____________ d. In the first half of the ovarian cycle, follicles secrete only estrogen; in the second half of the cycle, they secrete only progesterone. 4. The following statements pertain to the fetal circulation. Indicate whether each statement is true or false by writing the word “True” or “False” in the blank. Do not write T or F. ANS: a-T, b-F, c-T, d-T ____________ a. PO2 in the descending aorta is less than in the ductus venosus. ____________ b. Umbilical arterial blood has a higher PO2 than umbilical venous blood. ____________ c. It is possible for blood in the vena cava to reach the aorta without going through the left ventricle or left atrium. ____________ d. Shortly after birth, clamping the umbilical cord increases the total resistance of the baby’s systemic circulation. 5. Which organ(s) in the body receive(s) the most blood flow? (d) a. the digestive tract d. the lungs b. the kidneys e. the brain c. the heart f. the liver2 6. The graph on the right shows average daily levels of pituitary gonadotropin secretion in males and females throughout the lifespan. Briefly answer the following questions about the events depicted. Label the parts of your answer: a, b, c, d. a. What event triggers the increase in gonadotropin secretion around age 10? b. In males, why does gonadotropin secretion stop increasing in the late teen years and remain constant until about age 30? c. In males after age 30, why is there a slow, progressive increase in gonadotropin secretion? d. In females, why is there a steep increase in gonadotropin secretion in the early 40s? 7. The figure on the right shows a ventricular myocyte action potential. For each of the events listed below, write the appropriate letter(s) in the blanks to indicate when that event occurs. Do not guess; points will be subtracted for wrong answers. Don’t worry, you can’t get less than zero!  ____________ a. Time(s) when Na+ channels are open. ____________ b. Time(s) when K+ channels are open. ____________ c. Time(s) when Ca2+ channels are open. ANS: a-b; b-a,e,f; c-c,d Answer in box. ANS: a. Pulsatile release of gonadotropin releasing hormone (GnRH) from the hypothalamus. b. In males, testosterone secretion reaches its maximum level in the late teen years and remains high until around age 30. Testosterone feeds back and inhibits gonadotropin secretion, preventing further increases in the latter. c. After age 30 in males, there is a slow, progressive decrease in testosterone secretion, which relieves the negative feedback suppression of gonadotropin secretion. d. By the early 40s in women, there is depletion of the supply of follicles that are able to enter the ovarian cycle. So, estrogen levels begin to fall sharply. The sudden relief of negative feedback suppression causes a sharp increase in gonadotropin secretion.3 8. Indicate whether each of the following statements is true or false by writing the word “True” or “False” in the blank. Do not write T or F. ANS: a-F, b-T, c-T, d-F ____________ a. Slowing of action potential conduction through the sinoatrial node will slow the heart rate. ____________ b. Drugs that block K+ channels would be expected to prolong the plateau phase of the cardiac muscle action potential. ____________ c. Ca2+ ions are transported out of cardiac muscle cells by the Na+/Ca2+ exchanger. ____________ d. Small doses of quinidine, a drug that blocks fast Na+-channels, will increase the conduction velocity of the cardiac myocyte action potential. 9. Activity in sympathetic nerves to the atrioventricular (AV) node increases the conduction velocity of the pacemaker action potential through the AV node. Which one of the following is the most direct consequence of this increase in conduction velocity? (c) a. The atria and the ventricles contract simultaneously. b. Ventricular systole lasts longer than ventricular diastole. c. The time delay between atrial contraction and ventricular contraction is reduced. d. The rate of rise of the depolarization of the pacemaker action potential is diminished. 10. Indicate whether each of the following statements is true or false by writing the word “True” or “False” in the blank. Do not write T or F. ANS: a-T, b-T, c-F, d-T ____________ a. Atrial contraction plays a bigger role in ventricular filling as heart rate increases. ____________ b. The left atrioventricular (mitral) valve opens when left ventricular pressure falls below left atrial pressure. ____________ c. The time period between closure of the left atrioventricular valve and opening of the aortic valve is called the period of isovolumic ventricular relaxation. ____________ d. Throughout the ejection phase, aortic pressure is very similar to left ventricular pressure because the opening of the aortic valve is large and thus presents little resistance to blood flow. 11. Capillary blood pressure is normally about 30 mm Hg. However, capillaries in the feet may have blood pressure greater than 100 mm Hg in a standing individual. Briefly describe how capillaries, which are very