Exam 3 Posted Answers

Exam 3 Posted Answers - BISC 307 Spring 2009 Exam 3 Answers...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
BISC 307 – Spring 2009 Exam 3 Answers 5 pts. 1. Match each of the events of the ovarian cycle (on the left) with the day of the cycle (on the right) when that event occurs. Each day should be used only once. _____ 1. Progesterone from the corpus luteum peaks (d) a. Day 1 _____ 2. Estrogen positive feedback peaks (c) b. Day 7 _____ 3. One follicle becomes dominant (b) c. Day 13 _____ 4. Estrogen and progesterone are both decreasing (e) d. Day 21 _____ 5. Increase in FSH stimulates follicles to begin secreting estrogen (1) e. Day 26 7 pts. 2. There are 5 principal reproductive hormones in women: GnRH, FSH, LH, estrogen, and progesterone. State which of these could be used for hormone replacement therapy to treat the symptoms of menopause, and which (if any) could not be used for this purpose. Briefly explain your answer. ANS: Estrogen and progesterone could be used to treat the symptoms of menopause, but GnRH, FHS, and LH could not be used. During menopause, the ovaries no longer contain follicles capable of responding to FSH or LH. Therefore neither of these hormones will have any effect. Likewise GnRH, which stimulates release of FSH and LH, will not have any effect. Since the symptoms of menopause are caused by insufficient estrogen and progesterone, only direct replacement of these hormones would be effective. 5 pts. 3. Which one of the following changes would cause the greatest increase in O 2 consumption in cardiac muscle cells? (d) a. a decrease in aortic pressure b. a decrease in heart rate c. a decrease in contractility d. an increase in size of the heart e. a decrease in Na + influx during the action potential 8 pts. 4. In most places in the body, local hypoxia causes arterioles to dilate, which increases the flow of blood and oxygen to the hypoxic area. In the lung, however, the opposite is true, i.e., hypoxia causes constriction of pulmonary arterioles. Describe how this behavior of pulmonary arterioles helps explain why the foramen ovale in a baby’s heart closes quickly (within a minute) of birth. ANS: Because the lungs are not ventilated during fetal life, tissue there is relatively hypoxic and so pulmonary arterioles are constricted. This causes a high resistance in the pulmonary circulation, so little or no blood flows into the lungs. Instead, the higher pressure of the right side of fetal heart causes blood to pass from the right atrium to the left atrium through the foramen ovale. At birth, when the newborn baby inflates its lungs to take the first breaths, oxygenation of the lung triggers sudden dilation of pulmonary arterioles. The resistance of the pulmonary circulation falls, and so blood from the right ventricle flows into the lungs. The increased return to the left side of the heart through the pulmonary vein increases pressure on the left side. In addition, decreased flow of blood from the placenta causes a decrease in pressure on Page 1 of 5
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
the right side of the heart. This reversal of the pressure gradient between the right and left sides
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/28/2011 for the course BISC 307 taught by Professor Herrera during the Spring '08 term at USC.

Page1 / 5

Exam 3 Posted Answers - BISC 307 Spring 2009 Exam 3 Answers...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online