Difference between revisions of "Hypothalamus Differences in the Male and Female - Anatomy & Physiology"
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== Introduction == | == Introduction == | ||
| − | The [[Hypothalamus_- Anatomy & Physiology|hypothalamus]] is inherently female. [[Testes Endocrine Function_- Anatomy & Physiology|Testosterone]] 'defeminizes' the brain during embryogenesis and eliminates the GnRH surge centre in males. The female foetus has no testes to produce [[Testes Endocrine Function_- Anatomy & Physiology|testosterone]], thus | + | * The [[Hypothalamus_- Anatomy & Physiology|hypothalamus]] is inherently female. |
| + | * [[Testes Endocrine Function_- Anatomy & Physiology|Testosterone]] 'defeminizes' the brain during embryogenesis and eliminates the GnRH surge centre in males. | ||
| + | * The female foetus has no testes to produce [[Testes Endocrine Function_- Anatomy & Physiology|testosterone]], thus developes a [[Hypothalamus_- Anatomy & Physiology|hypothalamic]] GnRH surge centre. | ||
== Defeminizing the Hypothalamus in the Male == | == Defeminizing the Hypothalamus in the Male == | ||
| − | Testosterone crosses the [[Blood Brain Barrier - Anatomy & Physiology|blood-brain barrier]] and is converted into oestradiol. In the brain, oestradiol 'defeminizes' the [[Hypothalamus_- Anatomy & Physiology|hypothalamus]] | + | * Testosterone crosses the [[Blood Brain Barrier - Anatomy & Physiology|blood-brain barrier]] and is converted into oestradiol. |
| + | * In the brain, oestradiol 'defeminizes' the [[Hypothalamus_- Anatomy & Physiology|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 [[Testes Endocrine Function_- Anatomy & Physiology|testosterone]]. | ||
== The Female Hypothalamus == | == The Female Hypothalamus == | ||
| − | Foetal ovaries produce oestradiol, but this does NOT defeminize the [[Hypothalamus_- Anatomy & Physiology| | + | * Foetal ovaries produce oestradiol, but this does NOT defeminize the [[Hypothalamus_- Anatomy & Physiology|Hypothalamus]]. |
| − | + | * A protein called alpha-fetoprotein binds oestradiol to prevent it from crossing the [[Blood Brain Barrier - Anatomy & Physiology|blood brain barrier]], therefore oestradiol cannot effect the [[Hypothalamus_- Anatomy & Physiology|Hypothalamus]]. | |
| − | Alpha fetoprotein functions as | + | * 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 Cycle - Anatomy & Physiology|oestrous cycles]]. | ||
| + | * Between surges, there are low amplitude LH pulses. | ||
[[Category:Puberty]][[Category:Developmental Biology]] | [[Category:Puberty]][[Category:Developmental Biology]] | ||
| − | [[Category:A&P | + | [[Category:To Do - A&P]] |
Revision as of 15:01, 30 December 2010
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.