Lecture 36 Flashcards
Is the “sex typical behavior” universal?
No, not all the time
- variation across animals (sex-role reversal)
Is sex always for reproductive only?
no
- non-reproductive courtship/pairbonding/ sexual behaviors occur in many taxa within and between sexes
Describe the function of the anterior pituitary
Anterior pituitary contains non-neural endocrine cells under the control of hypothalamic hormones
Describe the HPG axis and how it regulates sex steroid secretion from the gonads in both sexes
1.) Hypothalamus secretes GnRH
2.) GnPH moves through hypothalamic- pituitary portal vessels
3.) GnPH acts on anterior pituitary
4.) Anterior pituitary secretes TWO hormones- FSH and LH
5.) FSH and LH acts on the gonads
6.) Gonads will release sex steroids
Male reproductive physiology
- Generation of mature gametes (sperm) at a steady rate after puberty
- External genitalia to deliver gametes to the female reproductive tract
-They are reproductive from puberty to their time they die
Female reproductive physiology
-Generation of mature gametes (eggs) on ca monthly cycle (menstrual cycle)
- internal genitalia and uterus to recieve male gametes for fertilization and support a developing offspring
- Parturition
- Lactation
Why are the fallopian tubes close to the ovaries?
So when ovulation happens, the egg can be brushed in to the opening of the fallopian tube (it can meet a sperm there and fertilization can occur)
What happens if fertilization implantation does not happen?
Uterine lining is shed (menstruation)
-not common in mammals
What does FSH in both sexes have affects on?
Gametogenesis (generation of gametes)
Females: oogenesis
Males: spermatogenesis
What does LH usually affect?
LH is associated with the secretion of the steroids
What are follicles?
Fluid filled aggregations of ovarian cells that have important endocrine functions.
1.) Eggs (oocytes) are encased in follicles
2.) They grow during the menstrual cycle (only a small number of them are activated during each menstrual cycle)
What is the important endocrine function of follicles?
- secretes hormones
-supports the egg
What is the follicular phase of the menstrual cycle?
- multiple follicles begin to develop (triggered to do that because of changes in endocrine signaling in HPG axis)
- One dominant follicle becomes dominant
- The dominant follicle matures and suppresses the other follicles from developing.
- Dominant follicle releases its egg into the fallopian tube (ovulation occurs)
-possible for more than one follicle to be dominant and more than one egg to be released during ovulation (twins)
Is the egg a mature gamete in the follicle?
No, egg has been arrested in meiosis one (not finished yet).
- Completes meiosis one right before ovulation happens
- Egg has to finishes meiosis two when it meets the sperm
What happens during ovulation?
Follicle opens up, releasing the egg out of the ovary and can be swept up by the fallopian tube
What happens to the remaining follicular tissues after the egg is released?
- different into the corpus luteum
- releases tons of sex steroids (estrogen and progesterone)
Luteal phase
The second phase of the menstrual cycle
- The corpus luteum functions (releasing sex steroids- one of the things the hormone is doing is causing the lining of the uterus to thicken and vascularize in preparation for implantation if fertilization were to happen)
- The corpus luteum degenerates
At the end of the luteal phase if no implantation or fertilization of an embryo, luteal function declines)
-sex steroids drops and then the uterine lining sheds
What happens in the luteal phase if fertilization happens?
Fertilization happens ovulation
- embryo implants in uterus
- corpus luteum will persist and not degenerate
- sex steroids continue to be pumped
- development of fetus
- parturition
What happens in the luteal phase if fertilization does not happen?
Corpus luteum degenerates and menstruation (uterine bleeding)
What happens to the anterior pituitary hormones (FSH and LH) levels in beginning of follicular phase?
FSH levels are increasing
- activates follicles and causes them to start maturing
What happens to the sex steroids (estrogen and progesterone) levels in beginning of follicular phase?
sex steroids lvls are low (negative feedback)
- not that much estrogen secretion= anterior pituitary releases more FSH
What happens when the dominant follicle do?
releases a lot of estrogen
- negative feedback still
causes decline of FSH levels
as estrogen levels rise, FSH levels decline.
What happens at late follicular phase and beginning luteal phase?
-high FSH and LH secretion
- LH surge corresponds with ovulation (causes ovulation)
- LH triggers dominant follicle to rupture and release the egg
- High estrogen levels as well (POSITIVE FEEDBACK)
Describe the negative and positive feedback of the the menstrual cycle
Negative feedback occurs throughout the cycle, but positive feedback occurs during few days causes the LH surge
- then it switches back to negative feedback
