1. NOTES: CH 46, part 2 – Hormonal Control / Reproduction

2. Hormones Involved in Reproduction - MALES
● Androgens: produced in Leydig cells in testes
(i.e. TESTOSTERONE)
● GnRH: from hypothalamus; stimulates anterior pituitary to release FSH and LH
● FSH: acts on seminiferous
tubules to increase sperm
production
● LH: stimulates androgen

3. *primary sex characteristics:
-development of internal and external reproductive organs
-sperm production

4. *secondary sex characteristics:
-deepening of voice
-distribution of facial & pubic hair
-muscle growth

5. Hormones Involved in Reproduction - FEMALES
● MENSTRUAL CYCLE = changes that occur in uterus
● OVARIAN CYCLE = changes that occur in ovaries

6. Menstrual cycle occurs in 3 phases:
1) Menstrual flow phase (3-5 days): endometrium is being shed from uterus
2) Proliferative phase (1-2 weeks): regeneration & thickening of endometrium

7. Menstrual cycle occurs in 3 phases:
3) Secretory phase (2 weeks): endometrium continues to thicken, becomes more vascularized & develops glands which secrete a glycogen rich fluid which serves as nutritional fluid for the embryo
(IF embryo does NOT implant in uterine lining by the end of this phase, a new menstrual flow phase begins)

8. Ovarian Cycle:
Follicular phase: several follicles in ovaries begin to grow
Ovulatory phase: follicle & adjacent wall of ovary rupture, releasing the egg
(2° oocyte)
(Follicular phase)

9. Ovarian Cycle:
3) Luteal phase: the remaining follicular tissue in ovary after ovulation becomes the CORPUS LUTEUM which is endocrine tissue that secretes hormones
(Luteal phase)

11. Menstrual and Ovarian Cycles are closely related:
● increased amts. of estrogen secreted by growing follicle stimulates endometrium to thicken in preparation for embryo
(PROLIFERATIVE PHASE)
● after ovulation, estrogen & progesterone secreted by the CORPUS LUTEUM stimulate continued development & maintenance of the endometrium
(SECRETORY PHASE)

12. Menstrual and Ovarian Cycles are closely related:
● decreased concentration of estrogen & progest. due to disintegration of the C.L. reduces blood flow to the endometrium; the endometrium breaks down & passes out of the uterus
● IF embryo is present, it secretes HCG which maintains estrogen & progest. secretion by the C.L. so the endometrium is maintained

14. MENOPAUSE Menopause: cessation of ovulation and menstruation
-between ages of 46 and 54
-ovaries lose their responsiveness to FSH/LH
-decline in production of estrogens

16. FERTILIZATION & IMPLANTATION
● fertilization occurs in the OVIDUCT
● female repro. tract produces secretions which capacitate sperm cells
● a capacitated sperm cell reaches the egg and must penetrate the ZONA PELLUCIDA

17. FERTILIZATION & IMPLANTATION
● when sperm cell binds to receptor molecules in zona pellucida, the ACROSOME releases its contents (i.e. digestive enzymes) so that it can penetrate the plasma membrane of the egg
(= “acrosomal reaction”)

18. FERTILIZATION & IMPLANTATION
● binding of sperm cell to egg triggers depolarization of egg membrane (functions as a “fast block” to polyspermy)
(= “cortical reaction”; a series of changes in outer zone, “cortex,” of the egg cytoplasm)

19. FERTILIZATION & IMPLANTATION
● CLEAVAGE (cell division) begins approx. 24 hours after conception
● after 3 days, embryo contains approx. 16 cells (MORULA)
● embryo reaches uterus approx. 7 days after fertilization & contains approx. 100 cells (BLASTOCYST)

20. FERTILIZATION & IMPLANTATION
● implantation occurs within next 5 days
● for the first 2-4 weeks, embryo obtains nutrients directly from endometrium
● in 2nd trimester, fetus secretes its own progesterone to maintain pregnancy

21. BIRTH
● high estrogen levels during the last weeks of pregnancy trigger formation of oxytocin receptors in uterus
● oxytocin secreted by fetus & posterior pituitary of mother stimulate smooth muscles of uterus to contract

22. BIRTH
● oxytocin stimulates prostaglandin secretion by placenta which enhances muscle contraction of uterus
● decreased levels of progesterone after birth remove inhibition from anterior pituitary which allows for prolactin secretion

25. BIRTH ● PROLACTIN stimulates milk production after 2-3 days
● OXYTOCIN controls release of milk from mammary glands

26. BIRTH CONTROL: Methods of Contraception:
COITUS INTERRUPTUS: withdrawal of penis before ejaculation
RHYTHM METHOD:
requires abstinence
from sexual intercourse
a few days before/after
ovulation

27. 3) MECHANICAL BARRIERS:
-condom (male, female)
-diaphragm
-cervical cap

28. 4) CHEMICAL BARRIERS:
-creams, foams, jellies w/spermicide
-easy to use, but high failure rate
unless used with a condom or
diaphragm

29. 5) ORAL CONTRACEPTIVES:
-“the pill”
-contain synthetic hormones to disrupt the ovarian cycle and prevent ovulation
-can be taken in pill form, injected, or implanted

30. 6) INTRAUTERINE DEVICE (IUD):
-small, solid object placed
within the uterus
-prevents implantation
of blastocyst

31. 7) SURGERY:
-in males: VASECTOMY
-in females: TUBAL LIGATION