Week 7- hormonal regulation of glucose Flashcards
1
Q
What are the islets of langerhans?
A
In the pancreas in the endocrine tissue- produce a range of hormones
2
Q
What are the cell types that make up the pancreatic islets?
A
Alpha cells-glucagon
Beta cells- insulin
Delta cells- somatostatin
Epsilon cells- ghrelin
3
Q
Explain insulin synthesis:
A
- insulin is synthesised as a single polypeptide which is then processed with disulphide bridges and proteolytic cleavage to produce mature insulin and C-peptide
- preproinsulin enters the secretory pathway in ER due to signal sequence
- proinsulin is transported through the golgi and packed into granules at the TGN
- mature insulin granules fuse with the plasma membrane to release insulin
4
Q
How do beta cells sense glucose?
A
By metabolising it
5
Q
What is the insulin receptor?
A
- Cell surface receptor tyrosine kinase
- Binding of insulin to receptor activates tyrosine kinase
- recruits and activates p13k- generated PIP3
- activates protein kinase B
- Inactivates glycogen synthesis kinase 3
- Results include- inhibition of lipolysis, increased glucose transport, stimulation of glycogen synthesis and effects on gene expression
6
Q
How does insulin act in the liver?
A
- Insulin stimulates glycogen synthase and inhibits glycogen phosphorylase = short term energy store as glycogen
- insulin stimulates glycolysis and suppresses gluconeogenesis
7
Q
What happens after an overnight fast?
A
- Low glucose and low insulin
- higher glucagon stimulates: glycogen breakdown and gluconeogenesis using lactate/pyruvate, alanine from skeletal muscle and glycerol from adipose tissue
8
Q
What are the types of hyperglycaemia?
A
- Acute-ketoacidosis, coma, fatality
2. Chronic- multiple organ damage, nephropathy, neuropathy, cardiovascular problems, retinopathy
8
Q
What are the types of hyperglycaemia?
A
- Acute-ketoacidosis, coma, fatality
2. Chronic- multiple organ damage, nephropathy, neuropathy, cardiovascular problems, retinopathy
