Unformatted text preview: the product of a series of
(hormone controlled) reactions controls its own
production by turning off the pathway when it reaches
a certain level. Each stage in the cycle is precisely
controlled by the interplay of various hormones and
the negative feedback effect that they have on their
controlling factors (hormones). Exemplar: e.g. one
hormone (e.g. estrogen) is produced as a result of the
activity of another hormone (e.g. FSH). At a certain
level, the estrogen inhibits further FSH release so
that the further development of follicles is prevented.
Estrogen levels then fall and the next stage in the
cycle can proceed. 3. In males FSH and LH (called ICSH in males) regulate
spermatogenesis (sperm production). Note that ICSH
operates through stimulating testosterone secretion. Biozone International 2009 Photocopying Prohibited 35
Hormone Main site of secretion Main effects and site of action during the menstrual cycle GnRH Hypothalamus Stimulates anterior pituitary to secrete LH and FSH. FSH Anterior pituitary Stimulates the growth of ovarian follicles. LH Anterior pituitary Stimulates ovulation and development of corpus luteum. Estrogens Graafian follicle At high level, stimulates LH surge. Promotes growth and repair of uterine lining. Progesterone Corpus luteum Maintains endometrium. Inhibits FSH/LH. Sharp drop triggers menstruation. Male Reproductive System (page 215)
(d) 2. (a) Conducts sperm to the urethra.
(b) Stores urine.
(c) Produces secretions that add to the semen (in
lower vertebrates and invertebrate the seminal
vesicles may store the sperm).
(d) Produces secretions that forms part of the semen.
(e) Conducts sperm and urine to the outside.
(f) Produces sperm and testosterone (male
(g) Holds the testes (outside the body at the cooler
temperature required for sperm production). 3. 4. 5. 6. Vas deferens
Prostate gland (c) Fusion of the egg and sperm membranes:
Enables the sperm nucleus to enter the egg.
The fusion causes a sudden depolariza...
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- Winter '13