1013 - Endocrine Pancreas and Blood Glucose Control Flashcards
Describe the Anatomic Location and Associations of the Pancreas
L1-L2, retroperitoneal (except the tail). Posterior to the stomach, between the duodenum (R) and spleen (L). Divided into head, neck, body, and tail.
Superior to the superior mesenteric artery, and inferior to the coeliac trunk. Pancreatic duct combines with common bile duct to open into the duodenum.
What are the functions of the pancreas?
Endocrine and exocrine functions.
Exocrine (97-98% of pancreatic mass) - produces digestive enzymes and bicarbonate, which are released into duodenum via pancreatic duct.
Endocrine (2-3% of mass) - produces hormones (particularly insulin, glucagon, somatostatin) which are released directly into bloodstream.
What is the stimulus for release of insulin?
Increased blood glucose is taken up by the cell, increasing ATP/ADP ratio. This closes ATP-sensitive K+ channels, depolarising the membrane and opening voltage-sensitive Ca++ channels. The influx of Ca++ induces insulin vesicle exocytosis of those vesicles nearest the membrane (not all).
Release augmented by other nutrients (FFAs, AAs etc), Incretins, and parasympathetic Nervous.
Release inhibited by Sympathetic NS and somatostatin.
What are the 4 types of GLUT transporter?
GLUT 1 - All cells, basal low-level glucose uptake
GLUT 2 - Particularly in liver and pancreatic beta cells - bidirectional, so that tissue can sense circulating glucose concentraiton
GLUT 3 - High-affinity in neurons and placenta
GLUT 4 - Insulin-regulated glucose transporter in adipose tissue and muscle.
What is the physiological effect of insulin?
Anabolic compound
Binds to an insulin receptor in skeletal and cardiac muscle, or adipose tissue, with phosphorylation of other enzymes leading to GLUT-4 transporters moving to the surface, markedly reducing glucose uptake. Also suppresses gluconeogenesis.
Stimulates AA transport, and promotes protein synthesis (anabolism)
Suppresses lipolysis, promotes VLDL secretion, and activates lipoprotein lipase, allowing fat uptake into peripheral tissues.
What is the stimulus for release of glucagon? What does it do?
Secreted from alpha-cells in response to low glucose or high AAs.
Activates gluconeogenesis and glycogenolysis in the liver, and activates lipolysis in adipocytes.
What is the stimulus for release of somatostatin?
Secreted from delta-cells in response to high glucose levels.
Inhibits insulin, glucagon, and growth hormone.
Name 4 stimulatory and 4 inhibitory actions of insulin.
Stimulates: Glucose uptake and glycolysis in muscles and liver Glycogen synthesis in muscle Lipogenesis in liver Protein synthesis in muscle Inhibits Gluconeogenesis Glycogenolysis Lipolysis FA oxidation and protein degradation.
