Physiologic Calcium Homeostasis
- calcium homeostasis is the summation of regulatory feedback systems involved in the control of plasma Ca concentrations;
- despite the small quantity of ionized calcium (as compared to the amount of calcium in bone), calcium is maintained in blood at a closely
- rate of passive Ca fluxes lies in cellular processes that influence and regulate calcium efflux from bone;
- two main hormonal regulators of calcium homeostasis are 1,25 Vit D and parathyroid hormone;
- calcium homeostasis allows rapid but controlled changes in calcium efflux, thru a negative feedback system between plasma calcium ion
levels and parathyroid hormone secretion;
- as a part of the feedback system active osteoblasts are capable of controlling extracellular environment needed for mineralization, while
also participating in control of plasma Ca concentrations;
- if adequate dietary calcium is not available, calcium is first released from bone surfaces;
- if dietary calcium deficiency continues, parathyroid hormone secretion rises, & rates of bone resorption are increased through
production & activity of osteoclasts;
- these cells digest all components of bone w/ the effect of adding calcium to extracellular fluid
Calcium flux and endogenous calcium content in isolated mammalian growth-plate chondrocytes, hyaline-cartilage chondrocytes, and hepatocytes.
Original Text by Clifford R. Wheeless, III, MD.
Last updated by Data Trace Staff on Friday, June 1, 2012 9:13 am