The Endocrine Pancreas Flashcards
What are the two functions of the pancreas
- Produces digestive enzymes secreted directly into the duodenum ( exocrine function )
- Produces hormones from the islets of langerhans ( endocrine function )
What makes up majority of mass of pancreas ?
Expcrine tissue (99%) vs endocrine tissue (1%)
Name important polypeptide hormones secreted from the pancreas and the type of cells they are secreted from
- Insulin beta cells
Glucagon alpha cells
Somatostatin delta cells
Pancreatic polypeptide ( PP cells )
Ghrelin e cells
Gastrin G cells
Vasoactive intestinal peptide VIP cells
What two hormones regulated blood glucose levels and what are their functions
Insulin which lowers blood glucose levels
Glucagon which increases blood glucose levels
What are the target tissues for insulin ?
Liver
Adipose tissue
Skeletal muscle
What are target tissues for glucagon
Liver
Adipose
What is the normal blood g,icosahedral level according to UHL
3.3-6mmol/L
What does the renal threshold mean ? And what is the normal value
The point at which the kidney cannot deal with the glucose level - normally they reabsorb all glucose back into the blood , however if glucose exceeds renal threshold then some glucose would not be reabsorbed and would be found in the urine.
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The renal threshold is 10mmol/L
In pregnant women ,renal threshold decreases and in the elderly it increases
What does glycosuria mean ?
Glucose is found in the urine
What are important properties of glucagon and insulin
Water soluble hormones - which means they do not need special transport proteins to carry them around in the blood.
They have a very short half life of 5 minutes
Outline the structure of pre pro insulim
A big peptide with an alpha helix structure
Consists of two unbranched peptide chains which are connected by 2 disulfide bridges to ensure stability.
51 amino acids
2 polypeptide chains
2 disulfide bridges
Outline the synthesis of insulin
- Translation of Pre-Pro-insulim ( a long polypeptide chain) occurs at the ER by the insulin gene.
- Cleavage of the PRE bit occurs agree ER.
- Pro insulin is transported to the Golgi.
- Pro insulin is now cleaved into insulin and C peptide.
- Both the insulin and C peptide is transported into a vesicle and marginates to cell surface where it remains to receive a signal.
Outline the process by which insulin is secreted from a beta cell
- When glucose levels are high , more glucose enters the beta cell which produces more ATP,
- ATP sensitive K+ channels detect this increase in ATP and shut. This causes the membrane to depolarise as K+ can no longer leave the beta cell.
- This depolarisation causes Ca2+ channels to open which causes an influx of Ca2+
- The influx of Ca2+ is what causes movement of vesicles containing insulin to fuse with the membrane and release insulin via exocytosis
What are the metabolic effects of insulin once it has been released from the beta cell ?
CARBOHYDRATE METABOLISM : increases uptake of glucose into cells via GLUT 4 channel. This increases glycolysis. Also glycogen synthesis increases and breakdown of glycogen is inhibited.
LIPID METABOLISM :
1. Decreases lipolysis in adipose tissue. Stimulates fatty acid and TAG synthesis. Increases uptake of TAG from blood. Decreases fatty acid oxidation in muscle and liver.
PROTEIN METABOLISM:
Increases transport of amino acid into tissues
Increases protein synthesis in muscle , adipose tissue
Decreases protein degradation.
Is insulin an anabolic or catabolic hormone ?
Anabolic hormone
