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Aldosterone: Regulating Nephron Activity

Aldosterone: Regulating Nephron Activity . Vincent Li . Basic Information. 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. Control & Homeostasis .

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Aldosterone: Regulating Nephron Activity

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  1. Aldosterone: Regulating Nephron Activity Vincent Li

  2. Basic Information • 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. Control & Homeostasis • 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 and Hypo-secretion • 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. Analogy • 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. Works Cited • "Addison's Disease: MedlinePlus Medical Encyclopedia." U.S National Library of Medicine. U.S. National Library of Medicine. Web. 09 Feb. 2014. <http://www.nlm.nih.gov/medlineplus/ency/article/000378.htm>. • "Aldosterone Blood Test: MedlinePlus Medical Encyclopedia." U.S National Library of Medicine. U.S. National Library of Medicine. Web. 11 Feb. 2014. <http://www.nlm.nih.gov/medlineplus/ency/article/003704.htm>. • "Aldosterone." WebMD. WebMD, 10 July 2010. Web. 11 Feb. 2014. <http://www.webmd.com/a-to-z-guides/aldosterone>. • "Bartter Syndrome: MedlinePlus Medical Encyclopedia." U.S National Library of Medicine. U.S. National Library of Medicine. Web. 11 Feb. 2014. <http://www.nlm.nih.gov/medlineplus/ency/article/000308.htm>.

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