endocrine pancreas

Question 1

what is the pancreas - location & function?

Answer 1

• the pancreas is an exocrine and endocrine gland located in the abdomen
• endocrine function is to regulate blood glucose levels

Question 2

what are the** islet of langerhans**?

Answer 2

• a region of the pancreas that contain endocrine (hormone producing cells)

Question 3

what are the 4 different cell types in the islet of langerhans

Answer 3

alpha cells - glucagon
beta cells - insulin
delta dell - somatostatin
PP cell - pancreatic polypeptide

Question 4

what is insulin, what cells secrete it and what stimulates its secretion?

Answer 4

• anabolic hormone produced by the beta cells of the islet of langerhans
• regulates amount of glucose in the blood
• stimulated by an increase in plasma glucose levels

Question 5

what part of the autonomic system inhibits insulin secretion?

Answer 5

the sympathetic system

Question 6

what part of the autonomic system stimulates insulin & glucagon secretion?

Answer 6

parasympathetic
note the sympathetic system stimulates glucagon secretion

Question 7

Describe the blood flow through the islet of Langerhans

Answer 7

• blood flow is from the core to the mantle (outside)
• beta cells get first pass on circulating glucose levels and that insulin can modulate activity downstream

Question 8

how is insulin stored?

Answer 8

in secretory vesicles

Question 9

Describe how the vesicles of insulin are released

Answer 9

• glucose is transported into the beta cell via facilitated diffusion through a glucose transporter (GLUT2)
• elevated conc of glucose in the ECF leads to elevated conc of glucose within the beta cell
• this leads to membrane depolarisation
• influx of Ca2+
• exocytosis of vesicles

Question 10

what is glucagon - function and what stimulates its secretion?

Answer 10

• hormone produced by the alpha cells of the islet of langerhans
• stimulated by a decrease plasma glucose

Question 11

what are the metabolic actions of glucagon?

Answer 11

• opposes the action of insulin- it signals that plasma glucose levels are low
• main targets are the liver, muscle & adipose tissue
• increases gluconeogenesis and glycogenolysis (to increase plasma glucose)
• increases lipolysis

Question 12

other than an increase in blood glucose concentration, what other factors influence insulin secretion from the beta cells?

Answer 12

• parasympathetic system
• increase in gastrointestinal hormones eg incretins (following food intake) eg GLP-1 & GLP
• an increase in blood amino acid concentration

Question 13

what** cells** secrete the incretin called GLP-1 (GIT hormones)?

Answer 13

• the L cells in the small intestine and large intestine

Question 14

what concentration of glucose in the blood initially stimulates insulin secretion & what concentration stimulates maximal secretion?

Answer 14

• initially - 6mM of glucose
• secretion is maximal at 20mM of glucose

Question 15

what are the metabolic actions of insulin?

Answer 15

• main target is liver, skeletal muscle and adipose tissue
• increases glucose uptake, glycogen synthesis, glycolysis in liver and skeletal muscle
• increases amino acid uptake in skeletal muscle
• decreases gluconeogenesis in liver
  increases the storage of fatty acids as triglycerides in adipose tissue

Question 16

what things** inhibit glucagon secretion**?

Answer 16

* high glucose in blood
* fatty acids
* somatostatin (GIT hormone)
* GLP-1 (GIT hormone)

Question 17

what are treatments used currently for type 2 diabetes?

Answer 17

• oral hypoglycemic drugs
• drugs that mimic GLP-1 alone are called GLP-1 receptor agonists

Question 18

how do the GLP-1 receptor agonists work?

Answer 18

they lower blood glucose by triggering the pancreas to release insulin after meals