1)  Explain the Major mechanisms controlling aldosterone release from the adrenal cortex

 2.)  Explain the Hormonal control of the level of calcium ions in the blood. PTH and calcitonin operate in negative feedback control systems that influence each other.

 

1.)  Explain the Major mechanisms controlling aldosterone release from the adrenal cortex

Aldosterone secretion is regulated by several known mechanisms, including the renin-angiotensin system, ACTH, and potassium. Additional new mechanisms participate in the control of aldosterone secretion including aldosterone-stimulating factor (ASF) and dopamine

 2.)  Explain the Hormonal control of the level of calcium ions in the blood

When the calcium level falls, the parathyroid glands release PTH into the blood and this signals cells in bone (osteoclasts) to release calcium from the bone surfaces. PTH also signals the kidney to reclaim more calcium before it is excreted in the urine and also stimulates synthesis of the active form of vitamin D

Step-by-step explanation

Aldosterone is synthesized in the body from corticosterone, a steroid derived from cholesterol. Production of aldosterone in the zona glomerulosa of the adrenal cortex is regulated by the renin-angiotensin system. Renin is secreted from the kidneys in response to variations in blood pressure and volume and plasma sodium and potassium levels. Renin acts on a protein circulating in the plasma called angiotensinogen, cleaving this substance into angiotensin I. Angiotensin I is subsequently converted to angiotensin II, which stimulates the release of aldosterone from the adrenal glands.

Blood calcium levels are regulated by parathyroid hormone (PTH), which is produced by the parathyroid glands. PTH is released in response to low blood calcium levels. It increases calcium levels by targeting the skeleton, the kidneys, and the intestine. In the skeleton, PTH stimulates osteoclasts, which are cells that cause bone to be reabsorbed, releasing calcium from bone into the blood.

PTH also inhibits osteoblasts, cells which deposit bone, reducing calcium deposition in bone. In the intestines, PTH increases dietary calcium absorption and in the kidneys, PTH stimulates reabsorption of the calcium. While PTH acts directly on the kidneys to increase calcium re-absorption, its effects on the intestine are indirect. PTH triggers the formation of calcitriol, an active form of vitamin D, which acts on the intestines to increase absorption of dietary calcium. PTH release is inhibited by rising blood calcium levels.

There are at least three hormones intimately involved in the regulation of the level of calcium in the blood: parathyroid hormone (PTH), calcitonin and calcitriol