Endocrine functions

• Pancreatic endocrine cells are clustered in the islets of Langerhans, that are embedded in the pancreatic exocrine tissue that secrete digestive enzymes.

• Endocrine cells include:

1. Beta cells that produce insulin a peptide that promotes the uptake and storage of nutrients by most cells.
2. Alpha cells that produce glucagon a peptide that maintains blood levels of nutrients after a meal and during stress.
3. Delta cells that produce somatostatin a peptide that inhibits digestion and absorption of nutrients by the gastrointestinal tract (Hill ET AL 2008).
   

• These hormones like all endocrine signals are secreted into the extracellular fluid and enter into the circulatory system.

Homeostatic regulation of cellular fuel:

• Insulin and glucagon are antagonistic hormones that regulate the concentration of glucose in the blood. The metabolic balance of cellular fuel in humans depends on maintaining a blood glucose level of approximately 90mg/100ml. When blood glucose levels exceed this level the pancreas secretes insulin into the blood. Insulin enhances the transport of glucose into the body cells and stimulates the muscle and the liver to store glucose as glycogen, thus lowering blood glucose levels. When blood glucose levels drop below set levels the pancreas secretes the hormone glucgon, which opposes the effect of insulin. Glucagon promoted the breakdown of glycogen in the liver and the release of glucose into the blood thus increasing blood glucose levels (Campbell, 2005).