Physiology Endocrine Pancreas

Insulin is a hormone produced by the beta cells of the islets of Langerhans in the pancreas. It's a key player in regulating blood glucose levels. Insulin plays a crucial role in stimulating glucose uptake by cells, promoting glucose storage as glycogen, and inhibiting glucose production by the liver.

Incretins are hormones like GLP-1 and GIP produced by the gut after food enters. They trigger insulin secretion, helping the body anticipate and manage the glucose influx from a meal.

Insulin secretion is stimulated by a complex process involving glucose entry into the beta cells, increased metabolism, and resulting changes in ion channels. This culminates in calcium release and ultimately, insulin release from the cells.

Insulin's primary actions are: Stimulating anabolism (building up), antagonizing catabolism (breaking down), and regulating ion transport in cells.

The IRS/PI3K/AKT pathway is a crucial branch within the insulin signaling pathway. This pathway plays a critical role in mediating insulin's effects on glucose uptake, primarily through the activation of GLUT4, and glycogen synthesis.

GLUT4 is a protein that acts as a glucose transporter. It is activated by the IRS/PI3K/AKT pathway, enabling the uptake of glucose into cells, especially muscle and fat cells.

Insulin suppresses glucose output in the liver by enhancing glucokinase and inhibiting G6Pase. It stimulates glycogen synthesis by activating glycogen synthase and inhibiting glycogen phosphorylase. It also inhibits gluconeogenesis by reducing pyruvate, lactate, and glycerol levels.

GLP-1 and somatostatin inhibit glucagon secretion, while cortisol enhances it. This helps regulate blood sugar levels by promoting glucose uptake and storage, while preventing excessive release of glucose from the liver.

Glucagon stimulates the liver to produce glucose via gluconeogenesis and glycogenolysis. Glucagon achieves this by promoting the production of specific enzymes (PEPCK, F16BPase, G6Pase) and activating glycogen phosphorylase while suppressing glycogen synthase, ultimately increasing glucose production.

The G protein-coupled receptor (Gs) pathway is the main mechanism by which glucagon stimulates gluconeogenesis and glycogenolysis in the liver. This pathway leads to a cascade of events that ultimately increase glucose production.

True. After a purely protein meal, amino acids directly stimulate both insulin and glucagon secretion. Insulin helps to prevent hyperglycemia by promoting glucose uptake and utilization, while glucagon prevents hypoglycemia by stimulating glucose production.

False. GLP-1 and GIP are incretins, which are produced and processed by L cells in the gut. Glucagon is primarily secreted by the alpha cells of the pancreas.

A hormone secreted by the alpha cells of the pancreas that increases blood glucose levels by stimulating glycogenolysis, gluconeogenesis, and lipolysis.

Insulin promotes glucose uptake by recruiting GLUT4 transporters to the cell membrane, allowing glucose to enter the cell.

Glucagon is a hormone that is released by the alpha cells of the islets of Langerhans in the pancreas.

Enzymes involved in gluconeogenesis (producing glucose from non-carbohydrate sources).

Insulin inhibits the production of these three enzymes, thereby reducing gluconeogenesis and lowering blood glucose levels.

Glucose and fatty acids suppress glucagon secretion, while amino acids stimulate it.

Insulin enhances glucokinase activity, which increases glucose uptake in the liver.

The liver, under the influence of insulin, suppresses glucose output by enhancing glucokinase and suppressing G6Pase.

Insulin promotes glycogen synthesis by stimulating glycogen synthase and inhibiting glycogen phosphorylase.

Insulin promotes glucose uptake by recruiting GLUT4 transporters, inhibits hormone-sensitive triglyceride lipase (HSL), and promotes lipoprotein lipase (LPL) in adipose tissue.