Endocrine-Topic2Sp10.pptx

Endocrine-Topic2Sp10.pptx - Topic #2 Endocrinology 1...

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Topic #2 Endocrinology 1 Regulation of Calcium and Phosphate through Parathyroid Hormone (Parathyroid Gland) & Active Vitamin D (Calcitriol), (Calcitonin (C Cells or Parafollicular Cells in Thyroid Gland)) Required Reading Reproduction: 7 th ed. pp. 780 - 796 5/18/10 1 Parathyroid Hormone increases in plasma calcium through action at bone, GI Tract & kidney. Requires Active Vitamin D for optimal affects . Active Vitamin D ( Calcitriol ) Some of the same actions as Parathyroid Hormone, but much less potent. [Calcitonin pharmacologically decreases in plasma calcium. Role in normal regulation plasma calcium uncertain since there are no know effects from its deficiencies.] Regulation of Plasma Calcium Critical - Muscle Contraction, Blood Clotting, Vesicular Transport, Release Neurotransmitters, Integrity and Function of Membrane Channels. Distribution Calcium in Body Plasma – 8.6 – 10.6 mg/dl. 1000 mg total content in plasma. If plasma concentration falls below 7 mg/dl increase membrane excitability. Loss of selective permeability, and tetany in skeletal muscles Bone - 1 x 10 6 mg or 1 kg 1. Soluble, rapidly mobilized Ca pool (Trabecular Bone) 2. Stable, slowly mobilized Ca pool (Cortical Bone)
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Topic #2 Endocrinology 2 Bone is a Reservoir for Calcium (& Phosphate) Releases Ca when Ca low, Takes up Ca when levels high 5/18/10 2 Bone – Collagen and Protein Matrix ( Osteoid ) in which Calcium, Phosphate, and Hydroxide (Hydroxyapatite Crystals ) deposited. Bone constantly undergoing Remodeling – Laying Down of Bone (Accresion ) and Breaking Down of Bone (Dismantling) . Remodeling occurs through activity of the Osteon – the Remodeling unit within the bone. Osteon has three cellular units 1. Oteoblast – Bone Formation. Cells responsible for laying down protein matrix and depositing hydroxyapaptite to form bone. 2. Osteoclast – Bone Dismantling. Cells, which differentiate from macrophages, responsible for bone breakdown – release of Calcium and Phosphate from bone into blood. 3. Osteocyte – osteoblast that is surrounded by formed bone. Cells no longer have the ability to lay down new bone. Balance between Osteoblast and Osteoclast activity determines if there is net bone Accresion or net Bone Dismantling, Respectively. Greater Osteoblast Activity Decrease Plasma Ca & PO4, & Bone Formation (Accresion) Greater Osteoclast Activity (Dismantling) .
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Topic #2 Endocrinology 3 Active Vitamin D - Calcitriol 5/18/10 3 Calcitriol (requires Parathyroid Hormone for normal physiological action on bones.) Normal absorbtion of Ca & PO4 from GI Tract & reabsorbtion Ca and PO4 filtered by the kidney. Normal bone formation (b/c required for absorption of Ca and PO4 from GI tract)
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This note was uploaded on 09/23/2010 for the course NPB 8746546 taught by Professor Goldberg during the Spring '10 term at UC Davis.

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Endocrine-Topic2Sp10.pptx - Topic #2 Endocrinology 1...

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