Paul Andersen describes four important homeostatic loops in biology. He begins with a brief description of the elements of a homeostatic loop. He then describes how the hypothalamus helps us maintain a stable internal body temperature. He explains the role of the pancreas (insulin and glucagon) in regulating blood glucose. He explains how the thyroid and parathyroid glands (along with calcitonin and PTH) regulation blood calcium. He also explains how the pituitary gland (and ADH) help regulate the osmolarity of the blood.