Menstual Cycle

Question 0

Ovulation

Answer 0

Estrogen levels increase during late follicular phase until they reach a level that causes a positive feedback increase spike of GnRH, LH, and FSH. Surge in LH causes ovulation

Question 1

Follicular phase

Answer 1

Begins with menstrual flow
GnRH secretion from hypothalamus in response to low estrogen and progesterone leases to secretions of LH and FSH which develop follicles. Follicles produce estrogen which through negative feedback lower GnRH, LH, and FSH levels. Estrogen retries endometrial lining

Question 2

Luteal phase

Answer 2

After ovulation, LH causes ruptured follicle to form corpus luteum which secretes progesterone which maintains uterine lining. Estrogen remains high, progesterone levels increase. High levels of progesterone and estrogen cause decrease in GnRH FSH and LH (prevent second ovulation)

Question 4

Menstruation

Answer 4

If implantation does not occur hCG not made and does not stimulate corpus luteum- progesterone levels decline and uterine lining is sloughed off. GnRH levels rise and cycle starts again

Question 5

Pregnancy

Answer 5

If fertilization occurs, hCG (secreted by blastula) maintains corpus luteum. Corpus luteum secretes estrogen and progesterone during 1st trimester. 2nd trimester, hCG decline, but placenta continues secreting estrogen and progesterone–inhibits GnRH secretion