What is the 6 steps of calcium level directly controlling the secretion of calcitonin and parathyroid hormone?
1. A higher than normal level of calcium ions in the blood stimulates parafollicular cells of the thyroid gland to release more calcitonin.
2. Calcitonin inhibits the activity of osteoclasts, thereby decreasing the blood Ca2+ level.
3. a lower than normal level of Ca2+ in the blood stimulates chief cells of the parathyroid gland to release more PTH
4. PTH promotes resorption of bone extracellular matrix, which releases Ca2+ into the blood and slows loss of Ca2+ in the urine, raising the blood level of Ca2+.
5. PTH also stimulates the kidneys to synthesize calcitriol, the active form of vitamin D.
6. Calcitriol stimulates increased absorption of Ca2+ from foods in the gastrointestinal tract, which helps increase the blood level of Ca2+.