Flashcards in MEH - Endocrine Pancreas Deck (15)
How does the pancreas develop embryologically?
An out-growth of the foregut
What are the two functions of the pancreas?
- produces digestive enzymes secreted directly into the duodenum (exocrine action)
- produces hormones from Islets of Langerhans (endocrine)
Give some examples of hormones secreted by the pancreas
- pancreatic polypeptide
- vasoactive intestinal peptide
Which two hormones control plasma glucose?
Insulin and glucagon
Why is it important that plasma glucose is kept stable?
The brain uses glucose at the fastest rate in the body and relies on the blood glucose
What transport proteins are used for insulin and glucagon?
Trick question - none, as they are carried dissolved in the plasma
How long is the half-life of insulin and glucagon?
Around five minutes - must be short due to constant changes in serum glucose levels
What is the structure of insulin?
It is an alpha-helix structured peptide, which consists of two unbranched peptide chains connected by 2 disulphide bridges to ensure stability
What is margination?
Movement of insulin storage vesicles to the cell surface and exocytosis
How do K ATP channels regulate insulin release from beta cells?
If glucose is present, it enters the cell and is metabolised. This increases cell [ATP], so the K ATP channels stay shut. The membrane depolarises and Ca2+ channels open, driving insulin release.
If no glucose was present, the K ATP channels would open and hyperpolarise the membrane, so no insulin would be released.
What is the structure of an insulin receptor?
Two identical subunits spanning the cell membrane - one alpha bit and one beta bit joined together by a disulphide bond (so four pieces in total: alpha+beta x 2)
What are the effects of insulin?
- increases glycogen synthesis
- increases uptake of amino acids in muscles
- inhibits breakdown of amino acids in liver
- increases storage of triglycerides in adipose tissue
What is glucagon secreted by?
Alpha cells due to low glucose levels
What is the structure of glucagon?
29 amino acids in one polypeptide chain - no disulphides bridges means it has a flexible structure