Think about… 4.1 Hormonal control of the menstrual cycle 4.2 Use of hormones Recall ‘Think about…’

2. Think about… 4.1 Hormonal control of the menstrual cycle 4.2 Use of hormones Recall ‘Think about…’ Summary concept map

3. Prevention of menstruation during sports games The performance of female athletes may be affected by their physiological conditions before or during menstruation.

4. Prevention of menstruation during sports games Some athletes may take drugs to prevent menstruation from occurring during sports games.

5. Prevention of menstruation during sports games The drugs contain hormones which are similar to those naturally produced in the female body. What are the hormones involved? How do the drugs prevent menstruation? Can menstruation be resumed later?

6. 4.1 Hormonal control of the menstrual cycle Let’s revise the menstrual cycle first.

7. The menstrual cycle Cycle repeats until meno…

8. The maturation and release of egg cells from the ovary are synchronized with changes in the uterus

9. The Ovarian Cycle • In the ovarian cycle • Hormones stimulate follicle growth, which results in ovulation • Following ovulation • The follicular tissue left behind transforms into the corpus luteum • Three phases: follicular --- ovulation --- luteal (1-14) (14) (14-28)

10. The Uterine Cycle Three phases : Menstrual -- proliferative ------- secretory (1-6) (6-14) (14-28)

11. 4.1 Hormonal control of the menstrual cycle Day 1 to 5 of the menstrual cycle • uterine lining breaks down • follicle begins to develop

12. 4.1 Hormonal control of the menstrual cycle Day 5 to 14 of the menstrual cycle • uterine lining begins to thicken • follicle becomes mature

13. 4.1 Hormonal control of the menstrual cycle Day 14 of the menstrual cycle • uterine lining becomes very thick • ovulation occurs

14. 4.1 Hormonal control of the menstrual cycle Day 14 to 28 of the menstrual cycle • uterine lining remains thick • ovum is moved along the oviduct

15. 4.1 Hormonal control of the menstrual cycle What are the hormones involved?

16. 4.1 Hormonal control of the menstrual cycle • events synchronized by the interaction of four hormones: pituitary gland follicle stimulating hormone (FSH) luteinising hormone (LH)

17. 4.1 Hormonal control of the menstrual cycle • events synchronized by the interaction of four hormones: yellow body follicle oestrogen

18. 4.1 Hormonal control of the menstrual cycle • events synchronized by the interaction of four hormones: yellow body progesterone

19. 4.1 Hormonal control of the menstrual cycle How do the hormones interact? • the hormones interact by feedback mechanisms

20. 4.1 Hormonal control of the menstrual cycle ovary pituitary gland stimulation  FSH

21. 4.1 Hormonal control of the menstrual cycle ovary pituitary gland  follicle develops

22. 4.1 Hormonal control of the menstrual cycle ovary pituitary gland  Above a certain level, oestrogen stimulates FSH and LH secretion

23. 4.1 Hormonal control of the menstrual cycle ovary pituitary gland  LH LH stimulates oestrogen secretion and oestrogen stimulates FSH and LH secretion …. A positive feedback effect at around day 14 that raise LH to a peak level

24. 4.1 Hormonal control of the menstrual cycle ovary pituitary gland  ovulation

25. 4.1 Hormonal control of the menstrual cycle ovary pituitary gland yellow body  LH stimulates development of yellow body and hence progesterone secretion

26. 4.1 Hormonal control of the menstrual cycle ovary inhibition pituitary gland  oestrogen and progesterone together inhibit LH and FSH

27. 4.1 Hormonal control of the menstrual cycle Let’s look at the menstrual cycle from day 5.

28. 4.1 Hormonal control of the menstrual cycle Before ovulation 1 The pituitary gland secretes FSH. 2FSH stimulates the development of follicles. As the follicle matures, it secretes more oestrogen. 3 Under the action of oestrogen, the uterine lining begins to thicken. to chart

29. 4.1 Hormonal control of the menstrual cycle Before ovulation 4 Oestrogen level continues to rise and reaches a peak just before ovulation. A high level of oestrogen stimulates FSH and LH secretion. The peaks of FSH and LH occur just after the oestrogen peak. 5 A high level of LH causes ovulation to occur on day 14. to chart

30. 4.1 Hormonal control of the menstrual cycle After ovulation 6 The remaining follicle cells form the yellow body. A high level of LH stimulates the yellow body to secrete oestrogen and progesterone. Oestrogen level rises again and progesterone level reaches a peak. 7 Under the action of oestrogen and progesterone, the uterine lining remains thick. to chart

31. 4.1 Hormonal control of the menstrual cycle After ovulation 8 High levels of oestrogenand progesterone together inhibit FSH and LH secretion. A low level of LH causes the yellow body to degenerate around day 24. to chart

32. 4.1 Hormonal control of the menstrual cycle After ovulation 9 The yellow body gradually stops secreting oestrogen and progesterone and the thickened uterine lining soon breaks down. Also, the inhibition of oestrogen and progesterone on FSH secretion is removed. The pituitary gland secretes more FSH again and the cycle repeats. to chart

33. 4.1 Hormonal control of the menstrual cycle levels of pituitary hormones in blood events in ovary levels of ovarian hormones in blood thickness of uterine lining to text

34. Cyclic secretion of GnRH* from the hypothalamus • And of FSH and LH from the anterior pituitary orchestrates the female reproductive cycle Five hormones involved in an elaborate scheme involving both positive and negative feedback *Gonadotropin-releasing hormone

36. Feedback control of human menstrual cycle Atresia of corpus luteum -- degeneration and resorption of corpus luteum in ovary Estradiol -- Oestrogen

37. Hormonal feedback control of menstrual cycle

38. The reproductive cycle of the human female

39. The reproductive cycle of the human female

40. 4.1 Hormonal control of the menstrual cycle If fertilization occurs … placenta secretes human chorionic gonadotrophin(HCG) • acts like LH • prevents degeneration of yellow body  secretes oestrogen and progesterone  uterine lining remains thick for embryo development

41. 4.1 Hormonal control of the menstrual cycle What is the significance of hormonal control of the menstrual cycle?

42. 4.1 Hormonal control of the menstrual cycle i) Ensure one ovum is released at a time • after ovulation, high levels of oestrogen and progesterone together inhibit FSH and LH secretion  prevents maturation of another follicle Higher survival chance!

43. 4.1 Hormonal control of the menstrual cycle i) Ensure one ovum is released at a time • after ovulation, high levels of oestrogen and progesterone together inhibit FSH and LH secretion  prevents maturation of another follicle Avoid wasting of energy!

44. 4.1 Hormonal control of the menstrual cycle ii) Prepare for implantation • oestrogen and progesterone stimulate the thickening of the uterine lining

45. 4.1 Hormonal control of the menstrual cycle iii) Prepare for the next possible pregnancy • if no fertilization occurs, levels of oestrogen and progesterone fall which causes menstruation to occur and the pituitary gland secretes more FSH again • the menstrual cycle repeats

46. 4.1 Hormonal control of the menstrual cycle 1 Hormonal control of menstrual cycle:

47. 4.1 Hormonal control of the menstrual cycle 2 Significance of hormonal control of the menstrual cycle: a After ovulation, levels of oestrogen and progesterone together inhibit FSH and LH secretion. high

48. 4.1 Hormonal control of the menstrual cycle 2 Significance of hormonal control of the menstrual cycle: a This prevents the maturation of another follicle and ensures only one ovum is released in each cycle. This would result in higher survival chance of the foetus.

49. 4.1 Hormonal control of the menstrual cycle 2 Significance of hormonal control of the menstrual cycle: b Oestrogen and progesterone stimulate the thickening of the uterine lining to prepare for the of the embryo. implantation

50. 4.1 Hormonal control of the menstrual cycle 2 Significance of hormonal control of the menstrual cycle: c If no fertilization occurs, levels of oestrogen and progesterone fall which causes to occur. The pituitary gland begins to secrete more again. menstruation FSH