endocrine pancreas

Question 1

embryological origin of the pancreas

Answer 1

foregut outpouching. its located behind the stomach

Question 2

functions of the pancreas

Answer 2

endocrine (1%)=hormone production from islets of langerhans. secrete into blood stream so have blood supply close by.
exocrine = produces digestive enzymes which are released into the duodenum + alkaline secretions. all secreted into ducts

Question 3

important hormones secreted by the pancreas

Answer 3

insulin - beta cells
glucagon - alpha cells
somatostatin - delta cells
ghrelin (hunger) - e cells
gastrin - G cells (stimulates gastric acid secretion)
pancreatic polypeptide - PP cells (regulator of all pancreatic secretions)
vasoactive intestinal peptide - VIP

Question 4

location of alpha and beta cells

Answer 4

alpha found at periphery and beat found in centre

Question 5

actions of insulin

Answer 5

increased glucose after feeding = absorption of glucose in liver, adipose and skeletal muscle
leads to carb, lipid and protein anabolism

Question 6

actions of glucagon

Answer 6

fasting - low glucose. release of glucose from liver and adipose. catabolism of mainly carbs and lipids

Question 7

why is it important to keep blood glucose levels tightly regulated

Answer 7

brain uses glucose really fast and relies on it being steady because its v sensitive to osmolarity e.g increased glucose will cause water t be drawn out of cells - don’t want brain cells shrinking

Question 8

normal, after meal and threshold levels of glucose

Answer 8

normal= 3.3-6mmol
after meal = 7-8mmol
renal threshol= 10mmol- if exceeds this then see glucose in urine

Question 9

general structure of glucose and insulin

Answer 9

water soluble
v short half life (5 min)
interact with cell surface receptors
receptor with hormone bound can be inactivated by internalisation

Question 10

specific structure of insulin

Answer 10

rigid structure

beat chain and alpha chain linked by disulphide bonds and C peptide ( which also helps to prevent vascular damage)

Question 11

describe insulin synthesis

Answer 11

1. pre-proinslun translation, signal cleavage and proinsulin folding in rER,
2. proinsulin transported to golgi
3. proinsulin cleaved to produce insulin and c peptide

Question 12

describe insulin regulation

Answer 12

glucose enters cell when concs are high
converted to ATP
K+ channels sense high TAP causing them to close = DEPOLARISATION
depolarisation causes opening of Ca2+ channels
ca2+ enters and influx causes vesicles containing insulin to fuse and exit via exocytosis

Question 13

actions of insulin

Answer 13

Increasss glucose uptake into target cells
increases glycogen synthesis
inhibits break down of fatty acids

in muscle - increases AA uptake = more protein synthesis
in adipose - increases storage of triglycerides
in liver- increases glycogen synthesis and inhibits break down of AA

Question 14

insulin receptor structure

Answer 14

receptor is a dimer - 2 identical subunits spanning the membrane. 2 subunits are alpha chain and 1 beta chain connected by single disulphide bond. alpha on exterior of cell and beta on interior. makes more sense if look at pic

Question 15

action of glucagon

Answer 15

glycogenolysis
glucogeneisis
- increases glycogen break down in liver
- synthesis of glucose from AA
- stimulates lipolysis to increase plasma fatty acids

Question 16

synthesis of glucagon

Answer 16

synthesised in RER, transported to Golgi where its cleaved and packaged and marginated below plasma membrane until called upon

Question 17

structure of glucagon

Answer 17

v flexible

7 polypeptide chain and no disulphide bridges

Question 18

effect of high glucagon on diabetes

Answer 18

makes diabetes worse. release more glucose = high glucose

Question 19

effect of low glucagon

Answer 19

contributes to hypoglycaemia

Question 20

diagnosis of diabetes

Answer 20

venous plasma glucose levels.
if fasting > 7mmol = diabetes
random >11mmol = diabetes
also glucose in urine, this cannot be used as a diagnosis though