Regulation of Calcium (Ca++) Balance

1. Importance of Ca++
1. bone is the "reservoir" of most Ca++ in the form of Calcium Phosphate (Ca++ with PO4-2)
2. primary physiological roles:
• at the muscle and neuron synapse
• essential for blood clotting process
• very critical in heart rhythms
2. Ca++ Regulation: Parathyroid Hormone (PTH) & Calcitonin
1. parathyroid hormone (PTH) - chief control when Ca++ begin to DECREASE too low
• bones - Ca++ and PO4-2 release to blood
• small intestine - activates Vitamin D which is essential for Ca++ resorption
• kidneys - Ca++ reabsorbed (but PO4-2 excreted)
2. calcitonin (thyroid gland) - released when Ca++ begins the INCREASE too high
• inhibits Ca++ release from bone, increases actual formation of Calcium Phosphate in bone

Category: Physiology Notes