L34. Hormonal Regulation

Question 1

GnRH

Answer 1

• hypothalamus

- release of the gonadotrophins

Question 2

FSH

Answer 2

• anterior pituitary
• stimulates sperm production in males
• stimulates follicle development in females

Question 3

LH

Answer 3

• anterior pituitary
• stimulates testosterone production in males
• stimulates ovulation in females

Question 4

Male hormones

Answer 4

• from testes
• testosterone
• inhibin

Question 5

Female hormones

Answer 5

• from ovaries
• estrogen
• progesterone
• inhibin

Question 6

Estrogen

Answer 6

• increased production with puberty
• stimulate bone and muscle growth
• female secondary characteristics
  > eg. breast development; fat deposition pattern
• maintains accessory organs and glands
  > CNS eg. libido
  > stimulating endometrial growth and secretion

Question 7

Spermatogenesis

Answer 7

NURSE (SERTOLI) CELLS- respond to FSH
> produce inhibin
> support and regulate sperm production

INTERSTITIAL (LEYDIG) CELLS- respond to LH
> produce testosterone
> testosterone has synergistic effect on FSH to make 1/2 billion sperm daily

Question 8

Oogenesis

Answer 8

• egg production
• oogenesis produces haploid gametes by meiosis
• produces one oocyte/ month (28 days) and is accompanied by cyclical changes in hormone levels (whereas spermatogenesis is continuous and billions of sperm are produced)

Question 9

Ovarian Cycle hormones

Answer 9

FSH
- stimulates growth and maturation of follicle
LH
- stimulates ovulation
- promotion of corpus luteum
ESTROGEN
- from follicle, and later corpus luteum
PROGESTERONE
- from corpus luteum to maintain lining (pro gestation)
INHIBIN

Question 10

Phases of the Ovarian Cycle

Answer 10

Pre-ovulatory/ Follicular Phase 
  - Day 1-13
Ovulation 
  - Day 14
Post-ovulatory / Luteal Phase 
  - Day 15-28

Question 11

Follicular phase (pre-ovulatory)

Answer 11

Day 1-5:
- hypothalamus releases GnRH –> ant.pit releases FSH, LH synthesised but not released
- FSH stimulates follicular growth
Day 6-13:
- About 20 follicles are stimulated to grow
> follicular cells produce and release estrogen and inhibin
- one follicle becomes dominant, the rest regress
- increasing estrogen and inhibin inhibit GnRH and FSH (neg feedback)
- when ovum is ready to leave, high levels of estrogen stimulate sudden release of LH

Question 12

Ovulation

Answer 12

Day 14 (after LH surge):
- egg and surrounding cells are released

Question 13

Luteal Phase (post-ovulation)

Answer 13

Day 15-28:
- remnants of follicle forms corpus luteum
> produces and secretes progesterone and estrogen
- PROGESTERONE promotes growth of uterine lining in preparation for implantation (with help of estrogen)

12 Days after ovulation
- Corpus luteum dies if no implantation occurs
> progesterone production ceases
> uterine lining is no longer maintained, sloughs off
> menses

Question 14

Phases of the Uterine (Menstrual) Cycle

Answer 14

Menses:
  - Day 1-7
Proliferative phase 
  - Day 8-14
Secretory phase 
  - Day 15-28

Question 15

Menses

Answer 15

Day 1-7:

• degeneration of functional zone
• constriction of arteries leads to degeneration of cells
• tissue sloughs off
• around 50 ml menstrual flow
• basilar zone blood supply unaffected

Question 16

Proliferative Phase

Answer 16

Day 8-14:

• ESTROGEN from follicles is the dominant hormone
• growth and vascularisation of endometrial lining
• mucous glands develop and start producing glycogen-rich mucous

Question 17

Secretory Phase

Answer 17

Day 15-28:

• uterine glands enlarge –> accelerated rate of secretions
• peak activity around 12 days after ovulation
• activities are supported by progesterone and estrogen from corpus luteum

12 days after ovulation:

• corpus luteum dies –> no more progesterone
• glandular secretions decrease
• lining no longer maintained
• cycle repeats with onset of menses

Question 18

Menarche

Answer 18

• first mentrual cycle

- usually age 11-12

Question 19

Menopause

Answer 19

• ovulation and menstruation stop
• usually age 45-55
• shortage of primordial follicles
• estrogen decreases; ovulation may not be triggered
• decreased estrogen:
  > osteoporosis (decrease in bone deposition)
  > neural effects (hot flashes, depression)
  > atherosclerosis risk