Exam 5: Puberty, Estrous, and Repro Behavior Flashcards
(89 cards)
Is puberty a process or an event?
Process
What is puberty?
Acquisition of reproductive competence
When does puberty occur?
When there is secretion of GnRH in appropriate frequency and quantity to stimulate gonadotropin release by the pituitary
What are the hypothalamic differences between a male and female?
The hypothalamus is inherently female with a tonic and surge center. Male only has a tonic center
Testosterone from fetal testis defeminizes hypothalamus and eliminates GnRH surge center
Testosterone is converted to E2 in the brain so it can defeminize the brain
Alfa-fetoprotein in females binds E2 and prevents crossing of blood-brain barrier
What are the definitions of puberty in females?
Age at first estrus or heat
Age at first ovulation
Age at which pregnancy can be maintained without deleterious effects
Is it easy of difficult to detect the age at first heat/estrus in females?
Easy
Is it easy of difficult to detect the age at first ovulation in females?
Difficult
Describe detecting the age at which pregnancy can be maintained without deleterious effects
Most practical
At time of 65% adult body weight
What are the definitions of puberty in males in chronological order?
Age of expression of behavioral traits Age at first ejaculation Age when sperm appear in the ejaculate Age when sperm appear in the urine Age when ejaculate contains a threshold number of sperm
What is puberty influenced by?
Plane of nutrition or “fatness”
Threshold body size and composition
Exposure to environmental and social cues
Genetics
What can puberty be influenced by in terms of genetics?
Breed variations and scrotal circumference in bulls and early puberty
What are examples of environmental and social cues?
Season of birth in seasonal breeders
Photoperiod in seasonal breeders
Presence or absence of opposite sex
Density of same sex groups
What species are effected by season of birth in seasonal breeders?
Sheep, goats, cats
What species are effected by photoperiod in seasonal breeders?
Sheep, goats, cats
What species are effected by the presence or absence of opposite sex?
Ewe, sow, cow, rodents
Describe the impact of density of same sex groups
Small groups reach puberty later
Large groups reach puberty sooner
What holds up puberty?
Failure of hypothalamus to produce sufficient quantities of GnRH to cause gonoadotropin release
Describe the prepubertal female
Tonic center in hypo release small quantities of GnRH at low frequency
Provides insufficient stimulation of pituitary
The minimal follicular development cannot release enough E2 to trigger surge center to release large amount of GnRH
What happens at the pubertal transition?
At low level of E2, the tonic center is very sensitive to neg. feedback on GnRH
Negative feedback is slowly lost which results in higher and higher level of GnRh which leads to more E2
Eventually the E2 is high enough to cause surge center to discharge large quantities of GnRH resulting in ovulation and puberty ensues
Describe the prepubertal male
Small amounts of testosterone/estradiol have negative feedback at hypothalamus
GnRH neurons become less sensitive to T and E2 as puberty approaches
More T and E2 are required to inhibit GnRH neurons
The decreased sensitivity leads to a negative feedback of T
Hypothalamus can now produce more GnRH and subsequently more FSH/LH is produced
What is the bovine age at puberty?
11 mos
What is the equine age at puberty?
14 mos
What is the ovine age at puberty?
7 mos
What is the porcine age at puberty?
7 mos
