The Endocrine Pancreas Flashcards
What is the pancreas?
a triangular gland with both exocrine and endocrine cells located behind the stomach
What do the acinar cells do?
produce enzyme rich juice for digestion
What do the pancreatic islets do?
produce hormones involved in regulating fuel storage and use
What are the cells contained within the islets and what do they produce?
b - cells - insulin
a- cells - glucagon
d - cells - somatostatin
F cells - pancreatic polypeptide
What is insulin?
protein hormone with 2 aa chains linked by disulphide bonds
How is insulin sythesised?
as proinsulin to produce 51AA insulin and Cpeptide 29aa
On what chromosome is the DNA for insulin?
11
What is the insulin synthesis pathway?
DNA -> mRNA -> preproinsulin (with signal peptide and c peptide) -> proinsulin -> insulin
Why is the signal sequence required?
to allow the hormone into the ER
What is insulin synthesis stimulated by?
glucose or feeding
What is the threshol of glucose-stimulated insulin secretion?
100mg/dl
How does glucose increase insulin secretion?
rapidly increases translation of mRNA and slowly increases transcription of DNA
What is the pathway for stimulating insulin release?
GLUT2 brings more glucose into the cell glucose is made into ATP ATP closes ATP sensitive K channel Cell depolarises and opens VGCC Ca stimulates vesicles to exocytose by using SNARE proteins
What are the stimulators of insulin secretion?
increase serum glucose, amino acids, FFA,ketone bodies
What are the inhibitors of insulin secretion?
decrease glucose, amino acids, FFAs, somatostatin and epinephrine
What are the inhibitors of insulin secretion?
decrease glucose, amino acids, FFAs, somatostatin and epinephrine
What is the low threshold for insulin production?
50mg/dl
When is insulin secretion half-maximal?
150mg/dl
When is insulin secretion at maximal response?
300mg/dl
Why is insulin secretion bi-phasic?
initial secretion of all insulin stores creates peak
then gradual increment as insulin is produced as long as blood glucose is high
What is glucagon?
29aa polypeptide that is a hyperglycaemic agent
What is the major target of glucagon?
glycogenolysis
gluconeogenesis
release of glucose to blood from liver cells
How is glucagon synthesised?
DNA -> mRNA -> preproglucagon-> proglucagon -> glucagon
What are stimulators of glucagon secretion?
decreased blood glucose, increased serum amino acids
stress
exercise
sympathetic nervous system
What are inhibitors of glucagon secretion?
somatostatin
insulin
increased blood glucose
What is somatostatin released in response to?
same things as insulin, increased blood glucose, amino acids, and fatty acids
what does somatostatin do?
decreases gut motility and secretion and inhibits gastrin , CCK and GIP
What is pancreatic polypeptide?
released in response to - ingestion of protein rich meal, low blood sugar, and strenuous exercise
What does the pancreatic poly peptide do?
inhibits gall bladder contraction and pancreatic exocrine secretion
