Can anyone summarize / explain this stuff to me in more simple terms?
Glucoregulation is the maintenance of steady levels of glucose in the body; it is part of homeostasis, and so keeps a constant internal environment around cells in the body.
The hormone insulin is the primary regulatory signal in animals, suggesting that the basic mechanism is very old and very central to animal life. When present, it causes many tissue cells to take up glucose from the circulation, causes some cells to store glucose internally in the form of glycogen, causes some cells to take in and hold lipids, and in many cases controls cellular electrolyte balances and amino acid uptake as well. Its absence turns off glucose uptake into cells, reverses electrolyte adjustments, begins glycogen breakdown and glucose release into the circulation by some cells, begins lipid release from lipid storage cells, etc. Circulatory glucose levels are the most important signal to the insulin producing cells, and as they are largely due to dietary carbohydrate intake, diet controls major aspects of metabolism via insulin. In humans, insulin is made by beta cells in the pancreas, fat is stored in adipose tissue cells, and glycogen is both stored and released as needed by liver cells. Regardless of insulin levels, no glucose is released to the blood from internal glycogen stores from muscle cells.
The hormone glucagon, on the other hand, acts in the opposite direction to insulin, forcing the conversion of glycogen in liver cells to glucose which is then put into the blood, though not from muscle cells, as they lack the ability to export glucose into the blood. The release of glucagon is controlled by low levels of blood glucose. Other hormones, notably growth hormone, cortisol, and certain catecholamines such as epinepherine have glucoregulatory actions similar to glucagon.