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Ch. 47 - Animal Reproduction and Development
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook
All textbooksFreeman 8th EditionCh. 47 - Animal Reproduction and DevelopmentProblem 13
Chapter 47, Problem 13

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In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?
Scientists confirmed the pill's mechanism of action by measuring plasma hormone levels in women before and after they went on the pill (* means P<0.05, ** means P<0.01, and *** means P<0.001). Do the data shown here support the hypothesis that the pill affects hormonal signaling?

Verified step by step guidance
1
Understand the mechanism of action of oral contraceptives: The pill typically contains synthetic hormones similar to progesterone and/or estradiol. These hormones work primarily by inhibiting the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland, which prevents ovulation.
Analyze the data presented in the image: The graph shows hormone concentrations before and while using the pill. The hormones measured are FSH, LH, estradiol, and progesterone. The statistical significance is indicated by asterisks, where * means P<0.05, ** means P<0.01, and *** means P<0.001.
Interpret the FSH and LH data: The graph shows a significant decrease in FSH and LH levels while using the pill compared to before using the pill. This supports the mechanism of action where the pill suppresses these hormones to prevent ovulation.
Evaluate the estradiol and progesterone data: Estradiol and progesterone levels are also significantly lower while using the pill. This indicates that the pill affects the hormonal signaling pathways, reducing the natural production of these hormones.
Conclude whether the data supports the hypothesis: The significant reduction in hormone levels while using the pill, as shown in the graph, supports the hypothesis that the pill affects hormonal signaling, confirming its mechanism of action in preventing ovulation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hormonal Regulation of the Menstrual Cycle

The menstrual cycle is regulated by a complex interplay of hormones, primarily involving follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, and progesterone. FSH stimulates the growth of ovarian follicles, while LH triggers ovulation. The balance of these hormones is crucial for normal reproductive function, and any disruption can affect fertility and menstrual regularity.
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Mechanism of Action of Oral Contraceptives

Oral contraceptives, commonly known as 'the pill', primarily work by delivering synthetic hormones that mimic natural hormones like progesterone and estradiol. These hormones prevent ovulation by inhibiting the release of FSH and LH from the pituitary gland, thereby preventing the ovarian follicles from maturing and releasing eggs. This mechanism effectively reduces the likelihood of pregnancy.
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Hormonal Signaling and Feedback Loops

Hormonal signaling involves the release of hormones into the bloodstream, which then bind to specific receptors on target cells to elicit a response. In the context of the menstrual cycle, feedback loops regulate hormone levels; for instance, high levels of estradiol can inhibit FSH and LH production. The data presented in the image suggest that the pill alters these hormone levels, supporting the hypothesis that it affects hormonal signaling.
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Related Practice
Textbook Question

The BMI z-score is a relative measure of body mass index (BMI) that takes into account age. Higher values represent heavier individuals for a given height. The table here shows the BMI z-score of pre- and post-pubertal girls at three ages.

Which of the following conclusions can you draw from the data?

a. At a given age, there are more girls with low BMI z-scores than with high BMI z-scores.

b. At a given age, girls with high BMI z-scores are more likely to have begun puberty than girls with low BMI z-scores.

c. Girls 11, 12, and 13 years of age are equally likely to have begun puberty.

d. There is no relationship between BMI z-score and age of beginning puberty.

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Textbook Question

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In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?

Which of the following is the most effective form of contraception?

a. Condom

b. Diaphragm

c. Withdrawal

d. The pill

548
views
Textbook Question

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In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?

Use your knowledge of the hormonal regulation of reproduction to predict the effect of a daily synthetic progesterone pill on (a) pituitary secretion of LH and FSH, and (b) ovarian secretion of estradiol and progesterone.

542
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Textbook Question

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In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?

Use the information in the graph to explain how the pill affects each of the following: (a) maturation of a follicle, (b) thickening of the uterine lining during the follicular phase, (c) probability of ovulation, and (d) volume of menstrual fluid.

662
views
Textbook Question

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In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?

Use Table 47.2 to compare and contrast the mechanisms of action of emergency contraception and mifepristone to that of the pill. Which methods act as contraception and which act to terminate a pregnancy? Explain.

581
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Textbook Question

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In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?

Imagine that four different contraceptives are under development. One blocks ovulation, one blocks fertilization, one blocks cleavage, and one blocks implantation. In the United States, which contraceptive is likely to be the least controversial to bring to market? Why?

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