Biology of Reproduction Summers

text: Human Reproductive Biology2nd Edition - Richard E. Jones & Kristin H. Lopez,: Read pages 24-28 for this lecture acronyms    end

VI. Feedback 			back to I. Endocrinology of the Reproductive System

	A. Homeostasis


		1. regulation of hormone levels


			a. control of basal levels


			b. control of pulsatile release


		2. Set Point


			a. level around which hormone concentrations
			   are regulated


	B. Negative Feedback


		1. e.g. Thermostat


		2. Long-Loop Feedback


			a. gonad is an intermediate


			b. feed back at
			   locus ceruleus, hypothalamus and pituitary


				i. ®- = site of feedback


		3. Short-loop feedback


			a. direct feedback by tropic hormones 


				i. LH + FSH inhibit GnRH
				   (at the hypothalamus and brain)


		4. Ultrashort Feedback


			a. releasing hormones and tropic hormones
			   feedback on themselves


				i. negatively  (and positively for GnRH)


	C. Positive Feedback


		1. Females


			a. Controls LH surge and therefore Ovulation


			b. Anterior Hypothalamic - Supraoptic - Suprachiasmatic
			   - Center = APS


				i. regulated by estrogen levels


					(1) a positive count of how much
					    E2 is in the blood


			c. Threshold E2 levels trigger APS stimulation
			   of  ARC + PON GnRH neurosecretory neurons


				i. NE + glutamate activate GnRH surge
				   (probably inhibited by endorphins too)


					(1) GnRH stimulates surge of LH


		2. Superultrashort = Paracrine GnRH feedback


			a. GnRH feedback  on ARC GnRH cells
			   plays a role in regulating pulsatile release