Endocrine pancreas Flashcards
What are the two parts of a pancreas?
- Exocrine
- Endocrine
What are the characteristics of an exocrine pancreas?
Contains ducts and acinar tissue
Glands secrete proteolytic enzymes along the ducts
These include
Trypsin and Lipase
What are the characteristics of an endocrine pancreas?
Islets of Langerhaans - 1 million
Made of different cells
- Beta cells - insulin
- Alpha cells - glucagon
- Delta cells - somatostatin
- Epsilon cells - ghrelin
What are the two most important pancreatic hormones?
Glucagon and insulin
What are the features of insulin?
Acts on tyrosine kinase receptor
These work by phosphorylation of proteins following activation Cascade of phosphorylation -> signalling pathways
2 important signalling pathways are activated:
- Anabolic pathways - lipogenesis, glycogenesis
- Increases GLUT4 translocation in muscle and adipose tissue
What are the features of glucagon?
Acts through G-protein coupled receptors
Increases intracellular cAMP upon activation
Activates catabolic pathways -> glycogenolysis and gluconeogenesis
What hormone can inhibit insulin and glucagon?
Somatostatin
How do B cells release insulin?
- Glucose enters the b cells via GLUT2 transporters
- The molecules are broken down into ATP
- Increase in intracellular ATP causes the potassium ATPase to block
- Potassium no longer leaves the cell
- The build-up of intracellular potassium causes membrane depolarisation
- Voltage-dependant calcium channels open
- Calcium enters the cells and causes vesicles containing insulin to fuse with the cell membrane
Why is insulin difficult to isolate?
Exocrine enzymes would degrade the insulin if you tried to make pancreatic extract
When was insulin first isolated?
In 1921 by Banting and Best
What did Sanger do in 1952?
Discovered the amino acid sequence of insulin
This was the first peptide to be sequenced
