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Puberty Endocrine Events - Anatomy & Physiology (view source)
Revision as of 09:30, 8 September 2008
, 09:30, 8 September 2008→Hypothalamic Neurone Release of GnRH
= Hypothalamic Neurone Release of GnRH =
* Hypothalamic development occurs gradually with growth of the animal.
* Hypothalamic development occurs gradually with growth of the animal.
== Female ==
* The Hypothalamus contains a tonic GnRH centre and a preovulatory GnRH 'surge' centre.
* The Hypothalamus contains a tonic GnRH centre and a preovulatory GnRH 'surge' centre.
* Before puberty can occur, full neural activity of the surge centre must be achieved.
* Before puberty can occur, full neural activity of the surge centre must be achieved.
* GnRH neurons must fire frequently and release large quantities of GnRH in order to cause the pre-ovulatory LH surge.
* The pre-ovulatory LH surge is a series of rapid, high amplitude pulses.
* Inability of the surge centre to function will result in failure to ovulate.
* In addition to the surge centre in the female, at puberty the tonic centre must also reach a functional state.
* The tonic centre regulates the tonic frequency of GnRH pulses.
== Male ==
* Does not develop a surge centre.
* The feedback system after puberty is a simple negative feedback loop.
* The negative feedback effect on GnRH is mainly due to some testosterone and mostly due to oestradiol because most testosterone is converted to oestradiol within the brain by aromatization.
* GnRH neurons become increasingly less sensitive to the negative feedback of testosterone and oestradiol as puberty approaches.
* Larger and larger quantities of testosterone and oestradiol are needed to inhibit the GnRH neurons.
* Thus, there is decreased sensitivity to the negative feedback of testosterone/oestrodiol.
* Therefore, the hypothalamus can produce increasing amounts of GnRH.
* Thus, more LH and FSH are produced until puberty is reached.