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Unformatted text preview: TA: Ishita Desai Handout #9 – TA Version Calcium and Bone- Linear growth of long bone occurs at the epiphyseal plates , where chondrocytes and osteoblasts are present. - A majority of Ca++ in the body is found in the bones/teeth. This Ca++ is in crystalline form and is called hydroxyapatite . This form of Ca++ dissolves when the pH decreases.- Extracellular Ca++ is maintained within a narrow range while intracellular Ca++ accumulates in the mitochondria and ER.- What does Ca++ do? Why do we need it? o Blood clotting o Exocytosis of NTs, hormones and other secretions o Regulation of excitability o Muscle contraction (cardiac, skeletal, smooth)- With the above actions in mind, if excitability is high and a patient is experiencing tingling/tetanus, what are his/her Ca++ levels? o Hypocalcemia o Mechanism: dec EC Ca++ fewer Ca++ ions neutralizing negative charges on proteins (EC side) of voltage-gated channels protein pulled outward even when membrane potential is at rest open channel increases excitability Ca++ and Parathyroid Glands- An increase in Ca++ decreases PTH secretion (by negative feedback inhibition)....
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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.
- Winter '09