Exam 2 Flashcards
What was William C. Young’s hypothesis?
Activational effects can vary person to person based on how the brain was organized with development hormones.
How are males and females sexually dimorphic for their pattern of HPG axis activity?
Males: have “tonic” activity (fairly steady levels of activity)
Females: have “phasic” activity (cyclical activity)
What is a follicle?
A Follicle is a sphere of granulosa cells surrounding the oocyte (egg). As the follicle matures, it becomes surrounded by an outer layer of cells called the theca cells.
What is a primordial follicle?
A single layer of granulosa cells surrounding ovum.
What is a zona pellucida?
Ovum develops an outer layer of glycoproteins that eventually binds sperm.
What is a secondary follicle?
Several layers of granulosa cells surrounded by a single layer of theca cells
What is a tertiary follicle?
Granulosa cells secrete fluid that accumulates within the follicle; theca differentiates into theca interna and theca externa layers
What is an antrum?
space between the oocyte and the outer wall of the follicle
What is liquor folliculi?
Juice in the antrum; rich in estrogens
What is a Graafian follicle?
During each cycle usually only 1 follicle becomes mature, the other 19 tertiary follicles die off.
When does ovulation occur?
Ovulation occurs when the graffian follicle ruptures, propelling the ovum towards the mouth of the fallopian tubes
What are the steps of estrogen and progesterone production in the ovary?
- LH stimulates theca interna to produce testosterone
- Testosterone diffuses out of theca interna cells and diffuses into granulosa cells.
- FSH stimulates granulosa cells to produce an enzyme - aromatase
- Aromatase converts testosterone to estradiol in granulosa cells.
- After ovulation, LH stimulates granulosa cells to produce progesterone and estrogen.
What is the menstrual phase? When does it occur?
Day 1-5.
Sloughing off of uterine lining; bleeding due to exposure of corkscrew blood vessel endings.
Very low progesterone & estrogen; LH & FSH increase by day 5
What is the follicular phase? When does it occur?
Days 6-12.
Development of follicles and mature egg.
Steady increase in estrogen, progesterone remains low.
What is the luteal phase? When does it occur?
Days. 15-21.
Preparation of uterus to receive fertilized eggs (pseudopregnancy in the absence of fertilization).
Estrogen after temporary dip returns to high levels, progesterone rises to high levels.
What is the corpus luteum?
Graafian follicle collapses and the granulosa and thecal cells become corpus luteum; produces progesterone and estradiol
What happens during 22-28 of the ovulation cycle?
In Absence of fertilized egg the luteal phase winds down; estrogen and progesterone levels decline. Withdrawal of progesterone from uterus triggers menstruation.
What is the corpus albicans?
The dying remnant of corpus luteal tissue.
What oral contraceptive pills are taken on days 22-28?
Placebo pills; absence of progesterone allows for menstruation
What is the mechanism of action of hormonal birth control?
Essentially “lock” the cycle into the luteal phase, thereby preventing follicle maturation and ovulation. Progesterone is the hormone that is only present after ovulation so its constant presence will prevent the follicular phase and maturation.
Progesterone in oral contraceptives prevents an LH surge by…
Maintaining high negative feedback on LH secretion
What is Plan B?
Plan B is a high dose of synthetic progesterone intended to suppress ovulation. It may also interfere with the ability of sperm to migrate into the fallopian tubes by thickening the cervical mucous.
What is RU486?
A synthetic progesterone receptor antagonist intended to cause miscarriage by inducing menstruation.
What is the negative feedback loop of HPG axis?
In response to low levels or estrogens and progesterone, GnRH and LH & FSH levels decrease.
What is the positive feedback loop of the HPG axis?
High levels of estrogen will trigger a GnRH surge, which in turn triggers an LH surge.
What causes a shift from negative feedback to positive feedback?
Negative feedback shifts to positive feedback after a threshold of estrogen exposure has been surpassed.
Where is the surge center?
Hypothalamus - anteroventral periventricular portion of the pre-optic area and suprachiasmatic nucleus.
What is the outcome of this experimental manipulation [2]?
Ovulation
What is the outcome of this experimental manipulation [3]?
No Ovulation
What is the outcome of this experimental manipulation [4]?
No Ovulation
What does the enzyme aromatase do?
Converts androgen to estrogens