Final answer:
Calcium homeostasis involves the skeletal system, endocrine system, digestive system, and urinary system, regulated by hormones PTH, calcitriol, and calcitonin. These hormones adjust bone resorption, calcium absorption in the intestines, and calcium reabsorption in the kidneys to maintain normal blood levels, which are crucial for various biological functions.
Step-by-step explanation:
The organs and hormones involved in Ca²⁴ homeostasis include the skeletal system (bones), the endocrine system (parathyroid glands and thyroid gland), the digestive system, and the urinary system (kidneys). The primary hormones responsible for regulating calcium levels are parathyroid hormone (PTH), dihydroxyvitamin D (calcitriol), and calcitonin.
The process works as follows:
- When blood calcium levels decrease, the parathyroid glands release PTH, which stimulates osteoclasts to release calcium from bones, increases calcium absorption in the kidneys, and facilitates calcium absorption in the small intestine, boosting the calcium level back to normal.
- If blood calcium levels increase, the thyroid gland releases calcitonin, which inhibits osteoclast activity, reducing calcium reabsorption in the kidneys and lowering the level of calcium in the blood.
- The kidneys also contribute by catalyzing the final step in the synthesis of active vitamin D (calcitriol) which aids in calcium regulation, and by directly regulating how much calcium is conserved or excreted in urine.
Hypocalcemia can lead to issues with muscle contraction, blood coagulation, nerve functioning, and bone strength, whereas hypercalcemia can cause lethargy, confusion, and even coma. Thus, these mechanisms are vital for maintaining a normal blood calcium level, which is crucial for many biological processes including muscle contraction, nerve impulse transmission, and blood clotting.