Lab 4: Reproduction Flashcards
What controls the release of follicle-stimulating hormone (FSH) and leutinizing hormone (LH)?
Where are they released from? What do they act on?
Release of gonadotropin releasing hormone (GnRH) by the hypothalamus controls secretion of 2 gonadotropins by the anterior pituitary. FSH and LH in turn act on the gonads.
What does FSH do?
FSH is required to intiate and maintain gametogenesis (production of sprem and oocytes)
What does LH do?
LH acts primarliy on endocrine cells to stimulate production of steroid sex hormones.
What is the long-loop feedback?
Gonadal sex hormones bind to receptors on the hypothalamus altering secretion of GnRH and also to receptors on the anterior pituitary altering secretion of FSH and LH.
What is short-loop feedback?
The pituitay gonadotropins bind to receptors on the hypothalamus and alter GnRH.
Describe the shift between positive and negative feedback in females.
Lower concentrations of estrogen have a negative feedback effect. However, when estrogen levels rise rapidly to a certain threshold level or above for at least 36 hours, right before ovulation, feedback changes from negative to positive, and LH is stimulated.
Describe the LH surge.
Immediately before ovulation, persistently high levels of estrogen aided by rising levels of progesterone, both released by the developing follicle, enhance secretion of GnRH from the hypothalamus via positive feedback. As a result, LH secretion by the anterior pituitary increases dramatically.
The LH surge causes ovulation of an oocyte from the Graafian follicle.
What is the corpus leuteum?
What does it secerete?
The ruptured follicle becomes the corpus leuteum. The main secretion is progesterone, which prepares the inner lining of the uterus for pregnancy.
What is the hormone human chorionic gonadotropin (hCG)?
hCG is secreted from the developing placenta to maintain the corpus leuteum and the continued secretion of progesterone and estrogen.
What happens if fertilization does not occur?
If fertilization does not occur, the corpus luteum degenerates, leading to a decline in estrogen and progesterone, and the onsent of menses.
How do you identify a positive result on an ovulation test?
What does that mean?
A positive result on an ovulation test is indicated by the test band being darker than the control band and means the women will be fertile over the next 3 days. Extra LH in the urine from the LH surge is binding to antibodies causing a reaction on the indicator strip.
How does a pregnancy test work?
During a preganancy test, hCG in the urine binds to an anti-hCG antibody and an indicator on a detection stick. If the woman is pregnant, the indicator will catalyze a color reaction and a test line will appear.
What is spermatogenesis?
What is it regulated by?
Spermatogenesis is the process by which spermatozoa are produced in males. Activation of FSH receptors in the Sertoli cells causes spermatogenesis.
What is testosterone?
What is it regulated by?
Testosterone acts to regulate GnRH via the long-loop pathway. Activation of LH receptor in the Leydig cells causes production of testosterone.
What is menopause?
Women’s reproductive cycle completely stop around age 51 when the ovaries no longer respond to gonadotropins and stop producing estrogen.
