Puberty Flashcards Preview

Repro Exam 2 > Puberty > Flashcards

Flashcards in Puberty Deck (37):

What increases in males when puberty begins?

sperm number
% motile sperm
% sperm with normal morphology


What increases in females when puberty begins?

fertility increases sometime after the first ovulation


What is puberty really?

a reactivation of the hypothalamo-pituitary-gonadal axis


What happens during the juvenile state that is different from puberty?

the hypothalamo-pituitary-gonadal axis is held in check by suppression of GnRH secretion from the hypothalamus


Developmental clock

times the genetic program for puberty and sets a lower age limit on its occurrence


Permissive signals

-provide signals to the developmental clock that may delay puberty if they are limiting
-if signals are not limiting, they cannot advance puberty earlier than the genetically preset lowest age


Where does the critical change for puberty occur?

hypothalamus; increase in frequency of GnRH pulses


Direct drive hypothesis

steroid-independent increased drive for GnRH secretion

(glutamate is most important stimulant, GABA is most important inhibitory)
(is the initial event decline in inhibition or increase in stimulation?)


Gonadostat hypothesis

secretin of GnRH during juvenile period is kept in check by negative feedback inhibition from gonadal steroids, but in puberty the sensitivity of the hypothalamus to the steroid feedback is changed


Explain what happens in female puberty in regards to GnRH

hypothalamus sensitivity to steroid feedback decreases, GnRH secretion increases, pituitary increases FSH and LH release, and full follicular development in the ovaries can occur


Initiation of puberty is most closely tied to what?

body growth rather than chronologic age

(making the developmental clock wait until the permissive signals are achieved is a protective mechanism)


What happens if you restrict dietary intake

retards growth and delays the time of puberty


How does photoperiod affect puberty?

seasonal breeders can only attain puberty within the breeding season


The interaction of these two factors will determine whether puberty is achieved for those animals that follow photoperiods

1. growth rate
2. their time of birth in the previous spring


How does time of birth affect puberty?

decides how much time they have to achieve the necessary target growth to initiate puberty


How does growth rate affect puberty?

determines how long it takes to achieve the target growth to initiate puberty


How do food supplies affect puberty?

seasonal variation in nutrition influence growth rate and thus the achievement of the metabolic gate


Name some social factors in attainment of puberty?



Vandenberg effect

hastening of puberty on exposure to males


Explain how sex differences affect puberty

-there are sexually imprinted differences in the controls over GnRH secretion
-testosterone removes the strict requirement for photoperiod alternations and thus puberty can occur earlier in males


What is anestrus?

absence of estrus or the absence of cyclicity


Juvenile anestrus

prior to puberty the animal is acyclic


Nutritional anestrus

in periods of nutritional stress and poor body condition, cyclicity ceases


Seasonal anestrus

seasonal breeders will be anestrus in the non-breeding season


Lactational anestrus

anestrus during lactation, varies between and within species


Suckling anestrus

suppression of cyclicity relies on the daily frequency of suckling episodes by bonded offspring


Milked anestrus

suppression of cyclicity relies on energy balance


Explain hypothalamo-pituitary-ovarian physiology in the first two-thirds of pregnancy

progesterone is high and therefore the dominant follicles can't go through final maturation and ovulation


Explain hypothalamo-pituitary-ovarian physiology in late pregnancy

progesterone and estrogen levels are high, which suppress FSH so follicle waves no longer emerge and the ovary is quiescent


Explain hypothalamo-pituitary-ovarian physiology after pregnancy

progesterone and estrogen levels fall, removing inhibitory feedback and FSH release occurs


Why does suckling cause anestrus?

suckling of a bonded offspring causes release of maternal endogenous opioid peptides (EOPs) in the hypothalamus and these suppress GnRH neurons


What factors influence the time it takes a dairy cow to have her first ovulation after calving?

-poor body condition and low voluntary intake
-BCS score
-low feed intake and catabolizing large amounts of body tissue
-increased feed intake in high producing cows (causes low circulation of estrogen)


Improved energy balance results in what?

-central inhibition of GnRH is lifted, permitting increased LH
-increased insulin stimulates receptors for growth hormone on the liver and the somatotropic axis is restored
-dominant follicles can now fully mature and secrete sufficient estrogen to give an LH surge


The first ovulation following improved energy balance will likely be what?

a silent heat


Behavioral anestrus

social anestrus
seasonal anestrus
post-partum anestrus
juvenile anestrus


What is senile anestrus?

when the number of primordial follicles falls below 1,000


What is pathologic anestrus?

when various systemic disorders cause anestrus by suppression of the hypothalamo-pituitary axis