Pancreatic Hormones Flashcards
What are the two divisions of the pancreas?
Endocrine
Exocrine
Function of the exocrine pancreas
Secretes digestive enzymes which aid absorption in the small intestine
Function of the endocrine pancreas
Secretes Insulin and Glucagon which metabolize nutrients after absorption
What are the Islets of Langerhans?
Clusters of pancreatic cells
What are the cells of the Islets of Langerhans?
α cells
β cells
δ cells
α cells
Function
Glucagon synthesis
α cells
Location in Islets of Langerhans
Periphery of the Islets
α cells
Function of glucagon
Causes liver and muscles to convert stored glycogen to glucose
β cells
Function
Produces insulin
β cells
Location in Islets of Langerhans
Center of Islets
β cells
Function of insulin
Uptake and storage of glucose in liver, muscles and adipose tissue
β cells
Autoimmune destruction of β cells causes …
Type 1 diabetes mellitus
δ cells
Function
Produces Growth Hormone-Inhibiting Hormone (GHIH)
Small polypeptide hormone
δ cells
Location in Islets of Langerhans
Scattered throughout the islets
δ cells
Function of GHIH
Inhibits GH and Prolactin
Regulates GI functioning
Inhibits Insulin and Glucagon secretion
Process of insulin synthesis
Precursor molecule Preproinsulin cleaved into Proinsulin
Proinsulin is packaged inside β cell granules
Enzymes cleave proinsulin into insulin and C-peptide residue
Upon stimulation, Insulin and C-peptide are secreted into the blood in equimolar amounts
What is the significance of C-peptide measurement?
Tested in hypoglycemic patients to determine cause
High Endogenous Insulin = High C-Peptide Level
High Exogenous Insulin = Low C-Peptide Level
What are the hormones which can be produced from proglucagon?
Glucagon
Glucagon-Like Peptide-1 (GLP-1)
Where is proglucagon cleaved into GLP-1?
Intestinal Cells
What type of molecule is GLP-1?
Incretins
Function of GLP-1
Lower serum glucose levels
Normal fasting blood glucose level
60-100 mg/dL
What is the effect of hypoglycemia?
Confusion
Loss of conciousness
What is the effect of hyperglycemia?
Tissue damage
What is the primary short-term storage form of glucose?
Glycogen
What happens when the liver is saturated with glycogen?
Stored as triglycerides
Triglyceride Formation
How are fatty acids formed?
Hepatocytes take up excess glucose and convert it to fatty acids
Free fatty acids are absorbed by adipocytes
Triglyceride Formation
How is glycerol formed?
Insulin stimulates adipocytes to absorb glucose and form glycerol
Triglyceride Formation
How are triglycerides formed?
Glycerol and Fatty acids are combined in adipocytes
Insulin and Glucagon travel ____ in the blood since they are ____
__unbounded__
__water-soluble peptide hormones__
What are the three primary actions which insulin and glucagon cause?
Insulin stimulates Glucose Uptake
Glucagon stimulates Glycogenolysis
Glucagon stimulates Gluconeogenesis
What type of receptor is the insulin receptor?
Tyrosine Kinase
What is the function of GLUT transporters?
Allow glucose uptake
GLUT Transports
Activation Process
GLUT Transporters
Types
GLUT1
GLUT2
GLUT3
GLUT4
GLUT5
GLUT Transporters
GLUT1 Locations
Found in most cells
Prevalent in brain and RBCs
GLUT Transporters
GLUT2 Locations
β Islets Cells
Liver Cells
GLUT Transporters
GLUT3 Locations
Brain
Placenta
GLUT Transporters
GLUT4 Locations
Adipose Tissue
Skeletal Muscle Cells
GLUT Transporters
GLUT5 Locations
Fructose transporter in Small Intestine, Muscles and Testes
Where does glycogenolysis occur?
In the liver where glucagon receptors are dense
Where does gluconeogenesis occur?
Mostly Liver
Some in Kidney
Gluconeogensis causes conversion of ____ into glucose
amino acids
A glucagonoma is a tumor of the …
Pancreatic α cells
Effects of glucagonoma
Hyperglycemia
Weight Loss
Diarrhea
Migratory Necrolytic Erythema (Red, blistering rash)
Where is regulation of insulin and glucagon controlled from?
Intrinsically at α and β islet cells
Extrinsically by ANS and GI hormones
Describe the insulin response to hyperglycemia
β cells are rapidly activated leading to insulin secretion
Insulin drops within 5 mins
Insulin increases again after 15 mins
Second stage causes insulin peak and plateau at 3 hours
Insulin Secretion Pathway
Glucagon Secretion Pathway
The central sensor for regulation in the ANS is …
the hypothalamus
How does the hypothalamus cause secretion of hormones?
Signals to endocrine pancreas to secrete Insulin or Glucagon
E.g. hypothalamus sends parasympathetic stimulus to islet cells to increase insulin secretion
Parasympathetic activity of hypothalamus causes …
increased insulin secretion
Occurs in rest-and-digest responses
Sympathetic activity of hypothalamus causes …
decreased insulin and increased glucagon secretion
Occurs in fight-or-flight responses
GI Regulation
Before eating there is …
anticipatory release of insulin
GI Regulation
What are the GI Hormones involved in digestion?
Cholecystokinin
Gastrin
GLP-1
Glucose-Dependent Insulinotropic Peptide (GIP)
GI Reulation
What are the effects of incretins?
Stimulate β cells
Inhibit α cells
GI Regulation
Which hormones are Incretins?
GLP-1
GIP
Which drugs can be used to treat hyperglycemia of T2DM?
Exenatide
Liraglutide
