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Puberty, Estrous Cycles, Repro Behavior (Smith)
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Puberty, Estrous Cycles, Repro Behavior (Smith) Puberty, Estrous Cycles, Repro Behavior (Smith) Puberty, Estrous Cycles, Repro Behavior (Smith)
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Physiology E2: Puberty, EstrousCycles, Repro Behavior (Smith)
_________ is the acquisition of reproductive competence - ANS Puberty
Puberty occurs when there is secretion of __________ in appropriate frequency and quantity - ANS
GnRH
Do males and females have a tonic center? A surge center? - ANS Both have a tonic center, only
females have a surge center
What defeminizes the hypothalamus in fetal males? - ANS Testosterone from fetal testis converts to
estrogen, crosses the BBB, and eliminates the surge center
In fetal females, _______________ binds estrogen and prevents crossing of blood-brain barrier so
the surge center remains - ANS Alfa-fetoprotein
In what fetal sex does Alfa-fetoprotein bind to estrogen? - ANS Females (lets the surge center
develop)
What are 3 clinical definitions of puberty in females? - ANS Age at first heat/estrus
Age at first ovulation
Age when pregnancy can be maintained without deleterious effects
Females can usually maintain a pregnancy without deleterious effects at ___% of adult body weight -
ANS 65%
What are clinical definitions of puberty in males (from youngest to oldest)? - ANS Expression of
behavioral traits
First ejaculation
Sperm appear in ejaculate
Sperm appear in urine
Ejaculate contains a threshold number of sperm (to achieve pregnancy)
What 4 factors affect when puberty occurs? - ANS Nutrition/fatness
Threshold body size/composition
Exposure to environmental and social cues
Genetics (breed, scrotal circumference of father)
What are 4 environmental and social cues that can influence when puberty occurs? - ANS Season of
birth
photoperiod in seasonal breeders
Presence of opposite sex
, Density of same sex groups
What animals have season of birth and photoperiod affect age at puberty? - ANS Seasonal breeders
(sheep, goats, cats)
Does larger groups of animal reach puberty faster or slower? - ANS Faster
Do fall or spring born sheep/goats reach puberty faster? - ANS Spring
Does the presence of an intact male increase or decrease time to puberty? - ANS Decrease (even if
no physical contact)
What is the major limit on puberty onset? - ANS Failure of hypothalamus to produce suff. quantities
of GnRH to cause gonadotropin release
True or false: Puberty does not start earlier because the anterior pituitary cannot yet produce FSH
and LH - ANS False
True or false: Puberty does not start earlier because the gonads do not yet respond to LH and FSH -
ANS False
True or false: Puberty does not start earlier because the hypothalamus does not produce enough
GnRH - ANS True
In a prepubertal female, the ________ center in hypothalamus releases small quantities of GnRH at
low frequency which is not sufficient to stimulate the pituitary - ANS tonic
How do females transition into puberty? - ANS Negative feedback on the tonic center is slowly lost;
higher and higher levels of GnRH lead to higher estrogen (E2) which eventually stimulates the surge
center
In a female approaching puberty, eventually ____________ is high enough to cause the surge center
to discharge large quantities of GnRH resulting in ovulation and puberty ensues - ANS estrogen
True or false: After a female's E2 is high enough to stimulate the surge center and discharges
adequate GnRH, normal cycling pattern arises - ANS True
In females, the ____ center is responsible for preovulatory surge - ANS surge
In males, small amount of _____/_____ have negative feedback on thehypothalamus - ANS
testosterone/estradiol
As males transition into puberty, GnRH neurons become ______ sensitive to T and E2 - ANS less
How do males transition into puberty? - ANS GnRH neurons become less sensitive to T and E2
negative feedback. The hypothalamus eventually produces enough GnRH to produce adequate
FSH/LH
What is the average age of puberty in cattle? - ANS 11 months
What is the average age of puberty in horses? - ANS 14 months
What is the average age of puberty in sheep, goats and pigs? - ANS 7 months
What is the average age of puberty in dogs and cats? - ANS 9 months (down to 4 months in cats and
up to 24 months in large dogs)
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