BISC 307 – Spring 2009
Exam 3 Answers
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
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.
explain your answer.
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.
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
cardiac muscle cells?
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.
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
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.
increased return to the left side of the heart through the pulmonary vein increases pressure on the
In addition, decreased flow of blood from the placenta causes a decrease in pressure on
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