Puberty Flashcards
Puberty depends on …?
…the ability of presynaptic neurons to turn on GnRH neurons -> ++GnRH secretion to “kickstart” reproductive system
Presynaptic neurons are influenced primarily by …?
…degree of fatness! hahaha A threshold body size and/or composition is required for the onset of puberty - can be influenced by genetics, nutrition…
T or F - environmental effects can alter the age of puberty
true - degree of influence varies between species
What is puberty?
age at which animal acquires reproductive competence
Difference between male & female hypothalamus?
Female has tonic AND surge centre
Male has only tonic centre
How does defeminisation occur?
oestrogen acts on hypothalamus eliminating ‘surge’ centre
How does E2 defeminise the male but not female?
In female, E2 released by fetal ovary -> binds to alphaFP (from liver and yolk sac) thus does not cross blood brain barrier and enter hypothalamus -> SURGE CENTRE DEVELOPS. In male, T4 released by foetal testis enters brain -> E2 -> SURGE CENTRE DOS NOT DEVELOP
Fundamental requirement of puberty?
sufficient GnRH prod by hypothalamic neurons
What does puberty result in?
gametogenesis
steroidogenesis
dev. of repro. tissues
T or F - puberty is limited by gonadotrophin producing ability of anterior pituitary
false
T or F - puberty is limited by ability of ovary to respond to gonadotrophins
false
First ovulation requires…?
achievement of full neuronal activity of the surge centre
Limiting factors in prepubertal animals…? (females/males)
Females - lack of gonadal oestradiol to stimulate surge centre
Males - lack of decreased hypothalamic sensitivity to -ve feedback by T4/E2
T or F - Response of GnRH neurons to +ve and -ve feedback is essential for onset of puberty
true
T or F - Decreased sensitivity to -ve feedback triggers the onset of puberty in males and females
true
Post pubertal heifers have what increase?
LH pulse frequency (from ~4 to ~18 pulses/24hrs)
Dev. of hypothalamic neurons in females influenced by …?
- nutritional factors (body size and/or composition)
2. exposure to certain environmental cond’s (season, photoperiod) or social cues
T or F - metabolic signals have no influence on puberty
false - metabolic signals influence GnRH neurons
Which 3 presynaptic neurons can stimulate GnRH neurons?
- leptin sensitive
- glucose sensitive
- FA sensitive
In dairy heifers, high/moderate.low plane of nutrition…?
high - 2lb/day (puberty ~7 months)
mod. - 1.5lb/day (~20 m)
low - 1.2lb/day (~>28 m)
Social cues moderating onset of puberty…
- presence or absence of opposite sex during prepubertal period (olfactory recognition via pheromones in urine)
- pop. density where animals housed (gilts in smaller group 2-3 -> delayed onset of puberty
T or F - male exposure > stimulation for onset of puberty than large groups of gilts
true
Fastest onset of puberty treatment for beef heifers?
high growth rate + bulls
Avg age of puberty in bovines, ovine, porcine
bovine - 11 mths both sexes
ovine - 7 mths both sexes
porcine - 7 mths both sexes
Advantages of accelerating or delaying puberty…?
Accelerating - minimise age of males -> accelerate genetic improvement by reducing generation interval
Delaying - in pets & vermin -> pop. control
