Pancreas Flashcards
Exocrine
secretions get dropped into a duct and the duct takes it to where it needs to go
endocrine
dump secretions into blood and they go everywhere
Anatomy of pancreas
- Head- mostly exocrine
- body- mostly endocrine
- Tail
Islets of Langerhans
Group of Endocrine cells
- alpha- releases glucagon (18-20% of endocrine cells)
- beta- releases insulin (73-75% of endocrine cells)
- delta- somatostatin (4-6% of endocrine cells)
What stimulates insulin secretion?
glucose
What inhibits glucagon secretion?
insulin
What is insulin composed of?
What is it synthesized from?
- Insulin is a peptide hormone
- composed of A and B chain joined by disulfide bonds
- synthesis: preproinsulin→proinsulin→insulin + c peptide
What is the half life of insulin?
where is it metabolized?
3-8 minutes
degraded by liver and kidney
What does C-peptide measurement indicate?
Half life of C-peptied?
C-peptide is measured as an index of endocrine capacity of the pancreas
about 15 minutes
What is the process for insulin secretion?
- glucose enters beta cell through GLUT2 transporter by diffusion
- glucose goes through glycolysis, turning ADP into ATP
- ATP is the ligand for the K channel. K channel closes.
- cell starts to depolarize with K channel closed
- Once cell depolarizes to threshold of voltage gated calcium channel, Ca channel opens and Ca rushes in
- Calcium causes release of insulin vesicles and the making of more insulin
When is glucagon released?
What is the target organ for glucagon?
when insulin levels are low
Target: liver
How does glucagon work when it gets to the liver?
- Glucagon binds to a GCPR (Gs)
- GPCR stimulates adenylyl cyclase and increases cAMP and thus PKA to phosphorylate target proteins
How does insulin get glucose into the cell?
- insulin binds to the GPCR
- GLUT4 transporter is recruited to the plasma membrane and facilitates glucose into the cell along with amino acids, K, Mg, and Phosphate.
GLUT1
widely distributed; gets glucose into cells all over
GLUT2
- found on Beta cells, kidney, intestines, liver
- low affinity, high capacity
- does not rely on insulin to transport glucose
GLUT3
supplies neurons with glucose
GLUT4
- Found in muscle and fat
- depends on insulin to get glucose into the cells
GLUT5
Intestines
can also transport fructose
SGLT1, SGLT2
Sodium dependent glucose transporters
found in Intestines and Kidney
Na-glucose co-transporters
Effects of insulin
- decreased appetite
- decreased glucagon
- increased glucose uptake by muscles and fat
- increased glycolysis
- increased glycogen synthesis
- increased triglyceride synthesis
- increased amino acid uptake
- increased protein synthesis
Effects of lack of Insulin
primarily because of glucagon
- increased appetite
- increased glucagon
- decreased glucose uptake by muscle and fat
- increase blood glucose
- increase gluconeogenesis
- increased lipolysis
- increased protein breakdown
- increase glycogenolysis
- Increase ketone body production
- decrease protein synthesis
What happens to:
insulin
glucagon
free fatty acids
blood glucose
liver glycogen
blood ketone bodies
As hours of starvation increases?
Type 1 Diabetes mellitus
Autoimmune destruction of Beta cells
about 10% of diabetes
Type 2 diabetes mellitus
Insulin resistance
about 90%
Mature onset diabetes of youth (MODY)
- Genetic defect in insulin production or release
- insulin will help, but not as much as oral meds that increas K channel sensitivity
- about 2% of young diabetics
Gestational diabetes
Any diabetes identified during pregnancy
*precursor to actual diabetes
How does Type 1 diabetes happen?
- Pancreatic Beta cells get destroyed.
- person gets some kind of bug
- body makes antigen
- proteins coming off the beta cell matches antigens too closely
- Beta cell gets attacked by immune system
- body continues to make the beta cells, but they all get killed by the antibodies
lipolysis
breakdown of fat
glycogen synthesis
liver making glycogen from glucose
gluconeogenesis
making glucose from non carbohydrates; lactate, glycerol, amino acids
*Important to get glucose to the brain. Everything else can survive on ketones. Happens in liver.
