Difference between revisions of "Hypothalamus Differences in the Male and Female - Anatomy & Physiology"
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m (Text replace - "-_Anatomy_%26_Physiology" to "- Anatomy & Physiology") |
m (Text replace - "[[Female_Reproductive_Tract_-Oestrous_Cycle_- Anatomy & Physiology" to "[[Oestrous Cycle - Anatomy & Physiology") |
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** Carrier of fatty acids | ** Carrier of fatty acids | ||
* As GnRH surges, LH and Oestradiol surge about every 20 days in the female. | * As GnRH surges, LH and Oestradiol surge about every 20 days in the female. | ||
− | ** Surge frequency varies between species, dependent on the length of their [[ | + | ** Surge frequency varies between species, dependent on the length of their [[Oestrous Cycle - Anatomy & Physiology|oestrous cycles]]. |
* Between surges, there are low amplitude LH pulses. | * Between surges, there are low amplitude LH pulses. | ||
[[Category:Reproductive System]] | [[Category:Reproductive System]] |
Revision as of 22:39, 30 November 2010
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Introduction
- The hypothalamus is inherently female.
- Testosterone 'defeminizes' the brain during embryogenesis and eliminates the GnRH surge centre in males.
- The female foetus has no testes to produce testosterone, thus developes a hypothalamic GnRH surge centre.
Defeminizing the Hypothalamus in the Male
- Testosterone crosses the blood-brain barrier and is converted into oestradiol.
- In the brain, oestradiol 'defeminizes' the hypothalamus.
- Surge centre function is minimized.
- Complete 'defeminization' of the brain requires postnatal exposure to androgens.
- Continued exposure to androgens is required to render the surge centre inoperative.
- As a result, LH does not surge, it maintains a relatively consistent episodic pattern of secretion every day.
- Episodes occur every 2-6 hours in the postpubertal male.
- Steady, pulsatile GnRH and LH release results in a steady, pulsatile release of testosterone.
The Female Hypothalamus
- Foetal ovaries produce oestradiol, but this does NOT defeminize the Hypothalamus.
- A protein called alpha-fetoprotein binds oestradiol to prevent it from crossing the blood brain barrier, therefore oestradiol cannot effect the Hypothalamus.
- Alpha-fetoprotein is synthesized firstly by the embryonic yolk sac and then by the foetal liver.
- Alpha fetoprotein functions as:
- Foetal blood osmotic regulator
- Carrier of fatty acids
- As GnRH surges, LH and Oestradiol surge about every 20 days in the female.
- Surge frequency varies between species, dependent on the length of their oestrous cycles.
- Between surges, there are low amplitude LH pulses.