Lecture 12

Lecture 12 - Calcium homeostasis, Exercise and Osteoporosis...

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Unformatted text preview: Calcium homeostasis, Exercise and Osteoporosis PSIO 201 Claudia Stanescu, Ph.D. Factors that influence bone 1) Dietary Minerals: calcium and phosphorus (also magnesium, fluoride and manganese) Vitamins: Vitamin A b stimulates activity of osteoblasts Vitamin C b needed for collagen synthesis Vitamin D b stimulates calcium absorption Vitamins K, B 12 b needed for synthesis of bone proteins 2) Exercise 3) Hormones Calcium homeostasis Goal : regulate blood calcium within a normal range (8.5 11.0 mg/dl) Why? Calcium has important physiological roles: Membrane excitability- Blood clotting Intracellular activity (second messenger) How? Control calcium entry into and exit from blood: Bone storage - Kidney excretion Intestinal absorption Calcium homeostasis Greenspanss Basic and Clinical endocrinolgy 8th edition. Metabolic Bone Disease Dolores Shoback, MD, Deborah Sellmeyer, MD, & Daniel D. Bikle, MD, PhD. 2007 ECF Ca2+ represents 1% of total body calcium yet it is highly regulated Hormones involved in calcium homeostasis Calcitonin Parathyroid hormone Calcitriol (Vitamin D) Calcitonin Stimulus : high blood calcium Source : thyroid gland (parafollicular cells) Target tissue : bone, kidney, intestine Actions (goal is to decrease blood Ca): Inhibits osteoclast activity (decreased bone resorption) Increases excretion of calcium at kidney Inhibits absorption of calcium at intestine End result: decrease blood calcium Parathyroid Hormone Stimulus : low blood calcium Source : parathyroid gland Target tissues : bone, kidney, intestine Actions (goal is to increase calcium): Stimulates osteoclast activity (increased bone resorption) Decreases excretion of calcium at kidney Stimulates intestinal absorption of calcium and promotes calcitriol (Vit. D) action End result: increase blood calcium Negative feedback 10 Blood Calcium (mg/dl) Calcitonin PTH Vitamin D...
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Lecture 12 - Calcium homeostasis, Exercise and Osteoporosis...

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