Lecture 7 Flashcards
Define puberty
Ability to successfully reproduce for the first time
What is the onset of puberty regulated by
Hypothalamus
What does puberty depend on
Hypothalamic neurons producing sufficient quantities of GnRH to promote and support gametogenesis
How does testosterone from foetal testis ‘defeminize’ the brain
Inhibiting the surge centre
What is responsible for inhibiting the surge centre
Oestradiol
Factors influencing the onset of puberty (4)
- Quality and quantity of food during growth and development
- Genetics
- Social conditions
- Season of birth and photoperiod
Signs of puberty in females (3)
- Age of first oestrus
- Age of first ovulation
- Age at which female can support pregnancy without deleterious effects (best measure)
Signs of puberty in males
- Age when reproductive behaviours expressed
- Age of first ejaculation
- Age when spermatozoa first appear in ejaculate
- Age when spermatozoa first appears in urine
- Age when ejaculate contains threshold number of spermatozoa
Do males have a positive feedback mechanism
no
What does testosterone inhibit
The surge centre which means it defeminizes
What defeminizes the brain
Oestradiol
How does a-fetoprotein prevent oestradiol from crossing the blood brain barrier
Binds to oestradiol meaning it cannot cross
Which of the structure actually ha to mature to begin puberty
Hypothalamus needs to undergo maturity
What tells the tonic centre of the hypothalamus to become less sensitive to negative feedback such as testosterone and oestrogen
concentrations of glucose, leptin and fatty acids in blood
What is the photoperiod triggered by
Melatonin
