L3 - Endocrine pancreas (L4.1) Flashcards
name of the group of cells in the pancreas
islets of langerhans
4 types of cells part of the islets of langerhans
- alpha
- beta
- delta
- PP cells
what do alpha cells secrete?
glucagon
what do beta cells secrete?
insulin + amylin
what do delta cells secrete?
somatostatin
what do PP cells secrete?
pancreatic polypeptide
describe the structure of insulin
2 AA chains (1 x alpha and 1 x beta)
linked by 2 di-sulphide bonds
intrasubunit disulphide bond in A chain
describe steps of insulin synthesis
- pre-proinsulin produced by ER
- transported to GA
- pre-proinsulin cleaved into proinsulin
- proinsulin cleaved into insulin + c-peptide
what substance is an indicator for the prescence of insulin? why?
c-peptide; as it is produced with insulin
what 3 things control insulin secretion?
- blood glucose
- neural stimulation
- hormones
why is glucose more effect orally than IV?
glucose in the GI tract is digested - GI hormones such as incretins can stimulate b cells to secrete insulin
4 stimulaters of insulin secretion
- parasymapthetic NS
- glucagon
- blood glucose
- GI incretins; GIP and GLP-1
2 inhibitors of insulin secretion
- somatostain
2. sympathetic NS
which vessel is insulin released into? which organ does this go to?
portal vein - liver
why is it better to use c-protein as an indictor for insulin rather than insulin?
c-protein has a much longer half life
how is insulin broken down?
proteolytic degradation
where is insulin broken down?
liver, kidney and muscle
is insulin the only hormone to reduce BG?
yes
2 long term effects of insulin
- increase/decrease key enzymes
2. stimulate cell proliferation
4 effects of insulin in the liver
- increased glycogenesis
- increased glycolysis
- increased lipogenesis
- decreased ketosis and synthesis of ketone bodies
4 effects of insulin in fat
- increased glucose uptake
- increased fatty acid uptake
- increased fat synthesis
- increased glycolysis
4 effects of insulin in muscle
- increased glycogenesis
- increased glycolysis
- increased glucose uptake
- increased uptake of AA
what effect does insulin have on the synthesis of ketones?
decrease