Changes

* The surge centre and the tonic centre in the [[Hypothalamus_- Anatomy & Physiology|Hypothalamus]] are anatomically distinct from one another.

* The surge centre and the tonic centre in the [[Hypothalamus_- Anatomy & Physiology|Hypothalamus]] are anatomically distinct from one another.

* The surge centre responds primarily to positive feedback stimulus.

* The surge centre responds primarily to positive feedback stimulus.

* In the pre-pubertal female, the sensitivity of the surge centre to the positive feedback of oestrogen is quite high, but [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulation]] does not occur.  This is because the immature [[Female_Reproductive_Tract_-The_Ovary_- Anatomy & Physiology|ovaries]] do not produce enough oestrogen to activate the highly sensitive surge centre.

* In the pre-pubertal female, the sensitivity of the surge centre to the positive feedback of oestrogen is quite high, but [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulation]] does not occur.  This is because the immature [[Ovary - Anatomy & Physiology|ovaries]] do not produce enough oestrogen to activate the highly sensitive surge centre.

* At these low levels of oestrogen, the tonic centre has high sensitivity to negative feedback stimulus, therefore it does not produce high levels of GnRH so LH and FSH levels also remain low.

* At these low levels of oestrogen, the tonic centre has high sensitivity to negative feedback stimulus, therefore it does not produce high levels of GnRH so LH and FSH levels also remain low.

* During the approach to puberty, the sensitivity of the tonic centre to negative feedback decreases, allowing increasing amounts of GnRH to be produced.

* During the approach to puberty, the sensitivity of the tonic centre to negative feedback decreases, allowing increasing amounts of GnRH to be produced.

* Increased amounts of GnRH lead to increased LH and FSH, which results in higher oestrogen production by the [[Female_Reproductive_Tract_-The_Ovary_- Anatomy & Physiology|ovaries]].

* Increased amounts of GnRH lead to increased LH and FSH, which results in higher oestrogen production by the [[Ovary - Anatomy & Physiology|ovaries]].

* When oestrogen levels reach a certain threshold, the surge centre is triggered by positive feedback.  This results in a massive discharge of GnRH.

* When oestrogen levels reach a certain threshold, the surge centre is triggered by positive feedback.  This results in a massive discharge of GnRH.

* This causes a surge in LH, so [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulation]] can occur and puberty ensues.

* This causes a surge in LH, so [[The_Ovary_-_Ovulation_- Anatomy & Physiology|ovulation]] can occur and puberty ensues.