Podcast
Questions and Answers
Which phase of the menstrual cycle is most variable in length?
Which phase of the menstrual cycle is most variable in length?
What is the primary hormone responsible for the positive feedback effect that triggers ovulation?
What is the primary hormone responsible for the positive feedback effect that triggers ovulation?
Which hormone is predominantly responsible for the negative feedback effect during the luteal phase?
Which hormone is predominantly responsible for the negative feedback effect during the luteal phase?
What structure is formed from the remnants of the follicle after ovulation?
What structure is formed from the remnants of the follicle after ovulation?
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Which hormone primarily acts on the thecal cells to stimulate androgen production?
Which hormone primarily acts on the thecal cells to stimulate androgen production?
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What is the name of the enzyme responsible for converting androgens to estrogen in granulosa cells?
What is the name of the enzyme responsible for converting androgens to estrogen in granulosa cells?
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Which of the following phases is characterized by a rapid increase in LH and FSH levels?
Which of the following phases is characterized by a rapid increase in LH and FSH levels?
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How many primordial follicles are women typically born with?
How many primordial follicles are women typically born with?
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What hormone is primarily responsible for stimulating the development of multiple follicles in the early follicular phase?
What hormone is primarily responsible for stimulating the development of multiple follicles in the early follicular phase?
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Which of these is NOT a characteristic of the dominant follicle?
Which of these is NOT a characteristic of the dominant follicle?
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The positive feedback loop that leads to ovulation is initiated by:
The positive feedback loop that leads to ovulation is initiated by:
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What hormone is primarily responsible for stimulating the production of progesterone by the corpus luteum?
What hormone is primarily responsible for stimulating the production of progesterone by the corpus luteum?
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The negative feedback loop that occurs during the luteal phase is primarily caused by:
The negative feedback loop that occurs during the luteal phase is primarily caused by:
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How does the dominant follicle become more sensitive to FSH?
How does the dominant follicle become more sensitive to FSH?
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What is the main function of inhibin in the follicular phase?
What is the main function of inhibin in the follicular phase?
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Which of the following statements accurately describes the difference in LH pulse frequency between the follicular and luteal phases?
Which of the following statements accurately describes the difference in LH pulse frequency between the follicular and luteal phases?
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Which of the following correctly describes the main function of LH during the luteal phase?
Which of the following correctly describes the main function of LH during the luteal phase?
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What causes the decrease in FSH and LH levels at the end of the luteal phase?
What causes the decrease in FSH and LH levels at the end of the luteal phase?
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Study Notes
Female Reproductive Endocrinology: Menstrual Cycle
- The menstrual cycle, a roughly 28-day cycle, is divided into follicular and luteal phases.
- Follicular phase: The first half, preceding ovulation; variable in length (10-14+ days).
- Luteal phase: The second half, following ovulation; more consistent length.
Hormonal Regulation of the Menstrual Cycle
- LH (Luteinizing Hormone) and FSH (Follicle-Stimulating Hormone): Peak at ovulation.
- Estrogen: Increases before ovulation.
- Progesterone: Low in the follicular phase, rises sharply in the luteal phase.
Ovarian Events During the Cycle
Follicular Phase
- Multiple follicles with ova develop.
- One follicle matures into a dominant follicle.
- Dominant follicle secretes Estrogen.
- Estradiol (a form of estrogen), triggers positive feedback loop leading to ovulation.
Luteal Phase
- Corpus luteum forms after ovulation, secretes both progesterone and estrogen.
- High progesterone levels trigger negative feedback loop.
Follicular Phase: Detailed Look
Early Follicular Phase
- LH stimulates androgen production in thecal cells.
- FSH stimulates aromatase activation in granulosa cells, converting androgens to estrogen.
Mature Follicle
- LH and FSH stimulate estrogen production.
- Estrogen increases FSH receptors in granulosa cells (positive feedback loop).
- Increased FSH receptors lead to more estrogen production.
Dominant Follicle
- High estrogen production and low androgen production make the dominant follicle.
- Estrogen increases FSH receptors for continued follicle development.
- FSH supports follicle growth & nutrient production for the ovum.
- Granulosa cells also produce inhibin, regulating FSH.
Key Takeaways: Follicular Phase
- LH triggers androgen production; FSH promotes estrogen synthesis.
- Estrogen enhances FSH sensitivity, leading to dominant follicle.
- Hormonal regulation selects the dominant follicle.
Luteal Phase
- Corpus luteum formation after ovulation.
- LH is the key for production of both estrogen and progesterone in the corpus luteum
- Both estrogen and progesterone are produced by LH stimulation.
- Progesterone and Estrogen create Negative Feedback
Hormonal Changes and Feedback Loops
Early Follicular Phase
- High FSH stimulates multiple follicles.
- Estrogen production increases from these follicles.
- High estrogen leads to negative feedback, suppressing FSH.
- Dominant follicle becomes highly sensitive to FSH.
Mid-Cycle (Ovulation)
- High estrogen from the dominant follicle triggers a positive feedback loop.
- Resultant surge in LH and FSH initiates ovulation.
Luteal Phase
- Corpus luteum produces estrogen and progesterone.
- Progesterone and estradiol, create negative feedback, reducing LH and FSH.
Pulsatile Hormone Secretion
- Frequent, low-amplitude LH pulses during the follicular phase (estradiol only).
- Slow, progesterone-infuenced LH and FSH pulses during the luteal phase.
Summary of the Menstrual Cycle
- Early Follicular Phase: FSH stimulates initial follicle development, LH stimulates androgen production; FSH converts to estrogen.
- Dominant Follicle: Highest estrogen output makes dominant follicle ; Estrogen promotes growth and heightened sensitivity to FSH.
- Ovulation: High estrogen triggers positive feedback loop, resulting in LH and FSH surge.
- Luteal Phase: Corpus luteum produces progesterone and estrogen, initiating negative feedback on hormone.
- End of Cycle: Corpus luteum regress; reduction of progesterone and estrogen results in next cycle initiation.
Key Points
- The menstrual cycle is a complex hormonal interplay.
- Understanding the hormonal feedback loops (positive and negative) is crucial to comprehension.
- Review the hormonal changes alongside the corresponding phases.
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Description
This quiz covers the menstrual cycle, detailing the follicular and luteal phases, hormonal regulation, and ovarian events. Understand the roles of LH, FSH, estrogen, and progesterone throughout this complex process. Dive into the biological mechanisms that regulate female reproductive health.
