W3006    Fall 1998   Physiology    First Exam     ANSWER KEY

1. Differentiation of the prostate requires T conversion to DHT, and the prostate remains sensitive to DHT throughout life.  The usual hormones involved are:

HYPOTHALAMUS --> GnRH --> ANTERIOR PITUITARY --> LH --> TESTES --> Testosterone --> DHT,  and T has negative
feedback effects on the hypothalamus and anterior pituitary gland. 

But the GnRH is normally released in pulses so that the concentration of GnRH seen by the ant pit is fluctuating.  If, instead, GnRH is infused at a continual rate, the constant (non-pulsatile) stimulation will lead to down-regulation of GnRH receptors on the ant pit, so there will be less release of LH, less release of T, and less DHT for stimulating the prostate.  (You got 5 points for having the correct hormones involved, 3 points for understanding the pulsatile nature of GnRH, 2 points for the rest.)

2. A.  HYPOTHALAMUS --> GnRH --> ANTERIOR PITUITARY --> LH + FSH  --> OVARY --> Estrogen + Progesterone, which both have negative feedback effects on the hypothalamus and anterior pituitary gland.  The ovary also produces inhibin, which has negative feedback effects on the ant pit, to inhibit FSH release.  Ovariectomy removes the negative feedback, so GnRH increases, and LH/FSH increase. 

B. LH is inhibited by E+P, while FSH is inhibited by E+P+inhibin.  Removing three inhibitory signals might be responsible for the greater increase in FSH, than results from removing two inhibitory signals of LH.

3. A.  HYPOTHALAMUS --> GnRH --> ANTERIOR PITUITARY --> LH + FSH  --> OVARY --> Estrogen + Progesterone.  The steroid hormones affect the development of the endometrium, the inner layer of the uterus.   Specifically, estrogen stimulates mitosis in the endometrium, so the layer thickens, and it also stimulates gland development.  In the presence of progesterone, the glands fill with secretions, and coiled blood vessels appear.  Hypophysectomy would remove the stimulus for E/P secretion, and the lack of these hormones would lead to a thin endometrium, without the glands and coiled blood vessels.

4. Normal situation:
FOLLICLE secretes estrogen, which stimulates endometrial thickening.  After the ovum is released (ovulation), the follicle becomes a CORPUS LUTEUM, which produces estrogen + progesterone, which further stimulate endometrial development.  After about two weeks (when the high E + P have inhibited LH for so long), the CL dies, removing the source of E+P.  As E+P levels decrease, endometrium looses its hormonal support, the tissue dies, and sloughs off as menstruation. 
This case:
There is no ovulation, so the follicle produces estrogen, stimulates endometrial buildup, but does not become a corpus luteum.  So the follicle keeps secreting estrogen, maintaining the thickened endometrium, which doesn't slough off, ie, no menstruation.

5. a. increases.  Under normal basal conditions (no lactation), the hypothalamus secretes a Prolactin Inhibiting Hormone, which is equivalent to dopamine, into the portal vessel connecting it to the pituitary.  This inhibits the ant pit from releasing prolacing.  There may also be a Prolactin Releasing Factor, that stimulates the pit to release PRL.  High PRL feeds back to the hypothalamus, to increase the PIH, thereby maintaining relatively constant levels of PRL.   High exogenous PRL would have the same effect, increasing the DA secreted into the portal vessel. 

6. osteoclast.  increase.  Calcium deposits will increase if osteoclasts are not functioning.

7. castration OR testes removal OR gonadectomy OR orchidectomy

8. A.  a. male.  In females, it would be appropriate for the Mullerian ducts to persist and develop.
B. MIH (MIS, or AMH) from the testes (Sertoli cells)  causes regression (degeneration) of the ducts
C. could be that 1) the testes don't make MIH or 2) the Mullerian ducts don't make receptors for MIH.

9.
A. y.  GhRH pulses become more frequent before the ovulatory LH surge.
B. y. CAH causes masculinization - penis-like structure.  AIS causes feminization - clitoris.
C. x. PTH causes loss of mineral from bone, so hypersecretion (too much) will decrease bone density
D. y. McClintock's article showed that a pheromone produced at ovulation lengthened the menstrual cycle
E. x. vasodilation in hot environment
F. x. epiphyses close, or decrease in thickness, after puberty.  Guevodoces look male after puberty.
G. x. with low calcium diet, Vitamin D will increase the absorption of dietary calcium, so a smaller percentage is excreted.
H. x. The kidneys are responsible for hydroxylating Vitamin D; intestines don't play a role in its production.
I.  x. Both are steroids, more or less equally have low water solubility.

10. autocrine or paracrine

11. hypothalamus (synthesized there, secreted from posterior pituitary gland)

12. radioimmunoassay

13. a. The sample used was random: they used the first women who came, and none dropped out during the study, which may have biased the results.
b. The participants were unaware of the source of the odors they were exposed to, so couldn't've been affecting the results because of their own expectations.
c. 9 different donor women were used, so this must be an effect that's not unique to Genevieve.
d. Women were using barrier contraception (ie, IUD and/or condom) rather than hormone contraception (pill), so they are being studied in the natural hormonal condition.
e. Rather than relying on subjects' memories re: last menstrual period, they conducted a hormonal assessment of stage of the cycle, by assaying urine to detect the ovulatory LH surge.
f. They used a crossover design - so that half the women saw folllicular compounds first, then ovulatory, and the other half  saw ovulatory first, then follicular.  In this way, they could be sure that the response to the second compound was not simply the result of repeated testing.
You basically got credit for mentioning any 2 of the above.  You lost credit for answers that suggested that you were basing your answer on the in-class discussion of earlier research, rather than on the reading.