Puberty & Seasonality – Male and Female Flashcards
What is puberty?
A developmental process in which endocrine and morphological changes transform the animal into an individual capable of reproducing
What is required for puberty to occur?
Secretion of GnRH at the appropriate frequency and quantity to stimulate gonadotrophin release by the anterior pituitary (development of the hypothalamus is important)
What are the differences between the male and female hypothalamus?
Female has a surge centre
What hormone is responsible for defeminising the brain?
Oestradiol, cannot enter as oestradiol in the female due to αFP, in the male testosterone enters the brain and is converted into oestradiol
What happens at puberty?
Pre-synaptic neurones stimulate GnRH neurones, stimulating the production of GnRH which in turn stimulates the production of gonadotrophins which cause gametogenesis, steroidogenesis & reproductive tissue development
What factors stimulate the pre-synaptic neurons?
Nutrition, environmental and social cues & genetics
How do the GnRH secreting neurons change during puberty?
Present before puberty, puberty determines the function, after puberty the GnRH neurones continue to secrete as they did before puberty, however frequency has increased
How is cycling initiated?
Frequency of pulses of LH increased through puberty until levels are high enough to initiate cycling
What actually limits puberty onset?
GnRH levels are too low to stimulate FSH/LH release
What happens at puberty onset in the female?
Low level oestradiol secretions from the gonad feedback negatively on GnRH production, at puberty this inhibitory effect is reduced meaning GnRH, and therefore LH & FSH, increase
What happens at puberty onset in the male?
As puberty approaches GnRH neurones become less sensitive to negative feedback effects of testosterone, therefore production is increased and this ultimately leads to puberty
What are the three main types of pre-synaptic neurones that can stimulate GnRH neurones?
Glucose sensitive, fatty acid sensitive & leptin sensitive – nutrition impacts on the age of puberty
What external & social factors affect female puberty onset?
Season when animal born, photoperiod that animal experiences at puberty, presence and absence of opposite sex just prior to puberty, density of same sex groups
What must happen before the breeding season can begin?
Hypothalamus must be able to produce GnRH
What are the seasonal effects on the male?
Low testosterone production, reduced or cessation of sperm production, reduced sperm motility, tests involute, behavioural factors alter
