Reproductive Endocrinology - Lecture 5 Flashcards
(56 cards)
Where is GnRH made, how and why is it released into the Anterior Pituitary?
In the Hypothalamus, it is released into the capillary bed of the median eminence, then to the second capillary bed in the Pituitary gland. It is released to help the Anterior Pituitary gland to release FSH and LH.
Where are FSH and LH made (2 Gonadotropins)?
In the Anterior Pituitary gland.
Which cells do FSH and LH act on?
The cells in the Gonads, testes in males and ovaries in females
What hormones do the Gonads produce?
Androgens, Estrogens and Progesterone
What are the two forms of GnRH release?
Pulsatile and Surge. There are two centres in the brain in the Hypothalamus that regulate this.
- Tonic centre
- Surge centre
How does the Tonic centre in the Hypothalamus release GnRH? And does this occur in males or females?
Responsible for the ongoing Pulsatile nature that occurs throughout the day every 1 to 3 hours. It is a pulsatile release of GnRH.
It occurs in both males and females.
How does the Surge centre in the Hypothalamus release GnRH? And does this occur in males or females?
It is responsible for a large surge or increase of GnRH.
It occurs in females only.
When does the Surge of GnRH occur in females?
Just before ovulation
Do high Estrogen levels result in a negative or positive feedback loop?
POSITIVE feedback loop
Which hormones are required for spermatogenesis?
Testosterone, LH and FSH
What are the 3 important accessory glands important for secretion of semen?
Seminal vesicle
Prostate gland
Bulbourethral gland
What produces semen?
The sperm plus the proteins and secretions from the glands = produce semen
Where is the mitochondrial spiral located in the sperm?
In the mid piece of the sperm, were energy is produced. to keep the flagellum (tail) moving
What do Androgens like testosterone influence?
- Primary sex characteristics - internal and external genetalia
- Secondary sex characteristics - body shape, beard and body hair, muscular development, lowering of voice, libido.
Describe the feedback regulation of the Gonadotropins FSH and LH.
LH and FSH from A. Pituitrary act on the Gonads (ovaries and testes)
LH acts on Endocrine cells to to create peptide and steroid hormones (Estrogens, progesterone & Androges)
The steroid hormones produced by LH act back on A. Pituitary go INHIBIT release of LH and FSH
The steroids produced by LH can act back on hypothalamic cells to INHIBIT GnRH
LH in females acts on Gamete production
FSH acts directly on Gamete production in both males and females
LH and FSH can act on GnRH to INHIBIT its release
When Estrogen is in HIGH concentration, does it INHIBIT or ENHANCE GnRH release? And who does it get help from to do this?
It ENHANCES GnRH release, and progesterone helps too.
What are Inhibins and Activins?
They are both peptide hormones that are made with the help of LH release in endocrine cells.
What do the peptide hormones Inhibins and Activins do?
They influence the release of FSH
In males, what does FSH and LH stimulate?
FSH - stimulates sertoli cells to produce proteins & inhibins.
LH - stimulates Leydig cells to produce testosterone
In females, what does FSH and LH stimulate?
FSH - stimulates ovaries to produce steroids estradiol & progesterone.
Surge (with LH) triggers ovulation
LH - stimulates ovaries to produce steroids.
Surge triggers ovulation
What is Leutinising hormone CRITICAL for?
The surge that produces ovulation
Where does spermatogenesis in the testes occur?
In the Seminiferous tubule.
Describe where in the Seminiferous tubule the Sertoli cells, the Leydig cells, the capillaries and Lumen are.
Capillaries - are around the outside of the tubule
Leydig cells are on the outside too
Sertoli cells are inside together the the spermatocytes
The lumen is in the middle of the tubule
What is the role of Sertoli cells?
Their role is CRITICAL. They provide nutrients and environment that the maturing spermatocytes need.
