Puberty and Estrous Cycles Flashcards
What is characteristic of males during puberty?
High testosterone and functional gametes
What is characteristic of females during puberty?
Age of 1st estrous is followed by ovulation and the initiation of a complete estrous cycle
What factors affect the initiation of puberty?
- Hormones
- Genetics
- Nutrition
- Environment
How do hormones affect the initiation of puberty?
- Reduced GnRH release
- Reduced pituitary release
- Reduced ovarian response
- Pineal gland stimulus - melatonin
How do genetics affect the initiation of puberty?
- Inbreeding causes delay of onset
- cross breeding will hasten onset
- different breeds have different times of onset
How does nutrition affect the onset of puberty?
- Under feeding an animal causes delay of onset
- Optimum feeding hastens onset
How does the environment affect initiation of puberty?
- Temperature and humidity (seasonally)
- Confinement = delay
- Presence of male hastens onset
What is the most important thing regarding onset of puberty?
The maturity of the hypothalamus
What is an advantage of having puberty start earlier?
Economic advantage - increased lifetime reproductive state
Why do short day breeders decrease/increase in breeding behavior when daylight decreases?
Their breeding behavior is controlled by the amount of melatonin in their system which increases as daylight decreases
What controls the endocrinology of puberty?
- Hypothalamus and gonads
- Negative feedback of estradiol
- Maturity of gonads
- rapid increase in steroidogenesis which causes gametogenesis to become functional
- Related more to body weight than age
What are the two centers that control GnRH surges in the hypothalamus?
Tonic center and Surge center
What does the tonic center control in females?
basal levels of GnRH (increases after puberty because pulse frequency increases)
What does the surge center control in females?
The preovulatory surge of GnRH (send out small pulses of GnRH before puberty)
What can the estrus cycle be affected by?
- nutrition and production of follicular waves
- Pharmaceutically controlled
What are the phases of the estrous cycle?
- Proestrus
- Estrus
- Metestrus
- Diestrus
- Post-partum anestrus
What happens during the proestrus phase?
- Preparation of mating
- Development of ovulatory follicle
- high estradiol, low progesterone
What happens during the estrus phase?
- acceptance from female
- Behavioral signs of estrus visable
- Highest ammount of estradiol, low progesterone levels
- Presence of large graafian/pre-ovulatory follicle
- Ovulation occurs after estrus ends
- hypothalamus, hippocampus and amygdala involved
what are some behavioral signs of estrus?
- Standing to be mounted
- Mounting other cows
- Rubbed rump and tail-head
- Chin resting
- Restlessness
- Increase in agonistic interactions (eg: head to head fights)
- Sniffing of the vagina of herd mates
- Flehmen reaction (wrinkling of the nose and curling of the lip)
- Frequent urination
What happens during metestrus?
- First few days after estrus
- formation of corpus luteum
- Bleeding
- Low estrogen, low progesterone
What happens during diestrus?
- Lasts until luteolysis (non-pregnant)
- Functional corpus luteum
- Low estradiol, high progesterone
- Associated with follicle turnover
What happens during post partum anestrus?
- Involution
- Suckling effect
Which phases of the estrus cycle happen during the follicular phase?
- Proestrus
- Estrus
Which phases of the estrus cycle happen during the luteal phase?
- Metestrus
- Diestrus
Which phases of the estrus cycle happen during the Anestrus phase?
- Post-partum anestrus
What happens during the anestrus phase?
- post-partum anestrus
- no expression of estrus behavior
- No ovulation/ no corpus luteum formation
- Follicular growth and turnover
What are the stages involved in a monoestrus cycle?
- Anestrus
- Proestrus
- Estrus
- Ovulation
- Implantation
- Gestation
- Parturition
- Lactation
What are the stages involved in a polyestrus cycle?
- Proestrus
- Estrus
- Ovulation (Metestrus if not pregnant)
- Implantation (Diestrus if not pregnant)
- Gestation
- Parturition
- Lactation
What does luteolysis do?
Determines the length of the diestrus phase and estrus cycle
What is the major luteolytic agent?
Prostaglandin F2alpha
Where is PGF2alpha synthesized?
By the uterus in the endometrium
What is PGF2alpha inhibited by?
conceptus in pregnant animals
Where are PGF2alpha receptors located?
in the luteal cells
What kind of receptor is the PGF2alpha receptor?
- membrane receptor
- G protein coupled
What does PGF2alpha do?
- Anti-angiogenesis effect
- Cell apocytosis
- Shuts down steroidogenesis enzymes
