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handout 80 - Calcium Homeostasis Ca2+ comes from. -enormous...

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Calcium Homeostasis Ca 2+ comes from. .. -enormous and continuous flux of Ca 2+ in body, but tightly regulated within narrow limits -[Ca 2+ ] in blood plasma and ECF is 1.25mM Regulation of Ca2+: Parathyroid Hormone (PTH): secreted when low/high extracellular Ca2+ (circle one) -secreted from parathyroid glands (4 glands) located behind the thyroid gland -PTH secreting cells have (Gq coupled receptor) ↑Ca2+ activates receptor IP3 ↑Ca2+ release in parathyroid cells inhibit PTH secretion low Ca2+ triggers exocytosis of PTH vesicles PTH secretion raise Ca2+ level -Functions: increases Ca 2+ -↑bone resorption ↑Ca 2+ , ↑Pi in the plasma -↑Ca2+ reabsorption, Pi reabsorption in kidney distal tubule -↑production of 1,25(OH) 2 D 3 from 25-OH-D 3 in kidney -↑Ca2+ reabsorption in intestine (indirect) Calcitriol (1,25(OH) 2 D 3 ): -active form of Vitamin D found in the body -Synthesis: 7-dehydrocholesterol present in cholecalciferol (Vit D3)
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This note was uploaded on 04/06/2012 for the course BICD 150 taught by Professor Fortes during the Winter '09 term at UCSD.

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handout 80 - Calcium Homeostasis Ca2+ comes from. -enormous...

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