1. Vincent Li

2. Steroid hormone secreted by the adrenal glands (that sit atop the kidneys) Acts on the distal tubules and collecting ducts of nephrons, making them reabsorb more Na + and water

3. Renin-angiotensin-aldosterone system (RAAS) A drop in blood pressure or volume in the afferent arteriole of the nephron causes the juxtaglomerular apparatus to release renin, an enzyme that initiates a chain of chemical reactions that ultimately yield a peptide called angiotensin II. Angiotensin II stimulates adrenal glands to release aldosterone, which causes distal tubules and collecting ducts to reabsorb more water and Na +, which increases blood pressure and volume.

4. Hyper-secretion of aldosterone can be caused by Bartter Syndrome (defect in kidney’s ability to reabsorb sodium), a benign tumor nodule in the adrenal gland, or a low-sodium diet. Hyper-secretion can result in loss of too much potassium from the body, as aldosterone also functions in potassium reabsorption. Hypo-secretion of aldosterone can be caused by Addison’s Disease (damage to adrenal cortex from infections like tuberculosis or HIV, hemorrhage, or tumors reduce hormone release) or a high-sodium diet. Aldosterone also functions in maintaining blood pH by forcing H+ ions into urine. Hypo-secretion will decrease this effect and cause the blood to become more acidic.

5. Take a colander (interior represents inside of the nephron tubule). The holes represent the pores of the aquaporins lining the tubule of a nephron. Aldosterone makes the aquaporins more permeable to water and sodium ions – think of the holes of the colander getting larger to let more water leave.

6. "Addison's Disease: MedlinePlus Medical Encyclopedia." U.S National Library of Medicine. U.S. National Library of Medicine. Web. 09 Feb. 2014.. "Aldosterone Blood Test: MedlinePlus Medical Encyclopedia." U.S National Library of Medicine. U.S. National Library of Medicine. Web. 11 Feb. 2014.. "Aldosterone." WebMD. WebMD, 10 July 2010. Web. 11 Feb. 2014.. "Bartter Syndrome: MedlinePlus Medical Encyclopedia." U.S National Library of Medicine. U.S. National Library of Medicine. Web. 11 Feb. 2014..