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Hormone Cycles
Pg. 394 Male
Hypothalamus releases GnRH
GnRH causes the pituitary to release:
• Male FSH which :
– Acts on sperm producing
cells
– Nurse cells (Sertoli)
release peptide
hormone which
slows/prevents FSH
production
• Male LH which:
– Acts on interstitial cells
to produce testosterone
which increases sperm
production
– High levels of
testosterone decrease
GnRH output
– This slows the release of
LH
Pg. 398 Female
1. FSH is secreted by the pituitary gland(day1)menstruation starts
2. About 1000 follicles in the ovary start to develop
but only one matures (goes through oogenesis)
3. The developing follicle secretes estrogen
4. Estrogen causes :1) the uterine lining to thicken
with mucus and blood vessels 2) secondary sex
traits
Lasts 10-14 days
5. High levels of estrogen in the blood cause 3) the
pituitary gland to stop releasing FSH (Negative
feedback)
6. Now the pituitary starts secreting LH
7. LH levels (when high) cause: 1) ovulation
about day 14
8. LH causes 2) the ruptured follicle to fill with
cells and fluid forming a yellow body called
the corpus luteum
9. The corpus luteum secretes progesterone
which : 1) maintains the lining of the uterus
(pregnancy hormone). It also 2) prevents new
follicles from developing by inhibiting the
release of FSH Lasts 10 to 14 days
10. if the egg is not fertilized, secretion of LH
stops as the corpus luteum breaks down and
the level of progesterone drops
11. the lining of the uterus is shed
12. As menstruation begins the levels of
estrogen and progesterone are at their
lowest so the pituitary starts to secrete FSH
so back to Day 1. 
• Cowper’s Gland – mucus and fluids which help
protect the sperm from acids – cleanses the
urethra
• Seminal vesicles – produce fructose for energy
to fuel the mitochondria of the sperm
• Prostate Gland – produces an alkaline buffer
to neutralize the strong acid vagina