SS2 Handout 7

SS2 Handout 7 - BICD 150 Megans Sections Handout 7 Topics...

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BICD 150 Megan’s Sections Handout 7 Topics: Calcium homeostasis; bone remodeling; calcium functions; hormones: parathyroid, Vit D, and calcitonin; adrenal cortex and medulla --------------------------------------------------------------------------------------------------------------------- ----------- Calcium Homeostasis and Bones Regulation of Plasma and ECF Ca2+ concentration Ca2+ is necessary for: o Blood clotting o Ca2+ signaling o Muscle contraction o Exocytosis (secretion and membrane proteins) The Ca2+ concentration in the cytosol is usually on the order of 0.1uM; Ca2+ outside the cell is kept at about 1.2mM (1.1-1.3 mM; very tightly regulated) o Ca2+/ATPase pumps (located in ER and plasma membrane) o Mitochondria take up Ca2+ o Ca2+ transporters, Na+/Ca2+ antiport o Ca2+ channels Parathyroid Hormone and calcitriol PTH Fig 9-2 of Endo text shows PTH levels vs. ionized Ca2+ o PTH increases the levels of free-floating ionized Ca2+ Stimulus o Low levels of extracellular Ca2+ Actions o Increases the Ca2+ concentration in the plasma o Dissolves CaPO 4 OH (hydroxyapatite) Increases free Ca2+ and free PO 4 o Kidney’s distal nephron: Increases Ca2+ reabs. Increases PO 4 excretion o Intestine Increases response to calcitriol (1,25(OH) 2 Vit D) Secretion o Ca2+ receptor on PTH gland cells Gq Increased Ca2+ activation of Gq increase IP3 and DAG increase in Ca2+ release (IP3’s effect) and increased PKC (DAG) causes increased Ca2+ release in the cell high levels of Ca2+ in the cell inhibit PTH secretion
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o Unusual because normally Ca2+ causes secretion o Exocytosis of PTH vesicles here is triggered by Mg2+ Calcitriol Actions--intestines o Increases Ca2+ absorption o Increases Ca2+ transport o Increases Ca2+ pumping Skin: cholesterol dehydrocholesterol
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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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SS2 Handout 7 - BICD 150 Megans Sections Handout 7 Topics...

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