Feedback Loops

Calcium 

Calcium homeostasis is the regulation of the concentration of calcium ions in extracellular fluid. The body goes through the following cycles in order to regulate calcium levels:

High -> thyroid gland releases calcitonin -> calcitonin -> stimulates calcium deposition in bones (store) / reduces calcium uptake in kidneys (flush out)

Low -> parathyroid glands release parathyroid hormone (PTH) -> PTH -> increases calcium uptake in kidneys / increases calcium uptake in intestines / stimulates calcium release from bones

Glucose

Glucose homeostasis, a part of metabolic homeostasis is the regulation of blood sugar levels. It is controlled by two enzymes: insulin and glucagon. The body goes through the following cycles in order to regulate glucose levels:

High -> Beta cells of pancreas stimulated to release insulin into the blood -> insulin -> body cells take up more glucose / liver cells take up glucose and stores it as glycogen -> blood glucose levels decline to a set point; stimulus for insulin release diminishes

Low -> alpha cells of pancreas stimulated to release glucagon into the blood -> glucagon -> liver breaks down glycogen and releases glucose into the blood -> blood glucose level rises to set point; stimulus for glucagon release diminishes 

Water

Osmoregulation is the regulation of water concentrations in the bloodstream. It controls the amount of water available for the cells in our body to absorb. The body goes through the following cycles in order to regulate water levels:

High -> kidney -> pee more

Low -> kidney -> aldosterone -> salt retention -> water retention

Low -> pituitary -> ADH -> collecting duct -> water retention

Low -> hypothalamus -> sensation of thirst -> drink water -> water retention