Gi Secretion Ii

Front 1

Is fluid hyperosmotic or hyposmotic when it leaves the stomach?

Back 1

hyperosmotic

Front 2

What area is considered to be the endocrine portion of the pancreas and what do they secrete?

Back 2

islets of langerhans - secrete insulin, somatostatin, glucagon, and pancreatic polypeptide; these are all secreted into blood

Front 3

What is secreted from the exocrine pancreas?

Back 3

enzyme, water, HCO3- secretion into pancreatic and common bile duct and thru sphincter of oddi

Front 4

What is the purpose of having both acinar and duct cells providing secretion in the pancreas?

Back 4

acinar cells - secrete enzymes
ductile cells - secrete water and electrolytes
** having 2 different secretion systems allows better adjustment of enzyme/liquid components

Front 5

What is the significance of osmolarity dropping rapidly in the duodenum?

Back 5

1) maintains fluid balance
2) provide digestive enzymes with ideal conditions
3) protection of mucosa

Front 6

What is the difference between proximal and distal duct cells in the pancreas?

Back 6

proximal duct cells - secrete water and bicarbinate
distal duct cells - reabsorbs water and bicarbonate

Front 7

What is the effect of increased flow rate on pancreatic secretions?

Back 7

1) high rates - net secretion is high in bicarbonate and low in chloride - reflective of primary secretion
2) vice versa at low rates - secondary secretion
*virually no change in cations wih change in flow rate

Front 8

What is stored in a zymogen granule?

Back 8

inactive proteolytic enzymes (proenzyme), and a trypsin inhibior (to avoid autodigestion of the pancreas)

Front 9

What are the different types of enzymes found in the exocrine pancreas?

Back 9

1) lipolytic (dig lipids)
2) amylases (dig CHO)
3) proteolytic (dig proteins)

Front 10

What does pancreatic lipase do?

Back 10

1) splits TGs into glycerol and FFAs (2FAs and a 2-monoglyceride)
2) requires oil/water interface, bile salts, and colipase

Front 11

What linkage does pancreatic amylase cleave?

Back 11

alpha 1,4 linkage of starch (creates maltose, maltotriose etc.)

Front 12

Trypsin, chymotrypsin, and carboxypeptidase A and B are considered to be what general type of pancreatic enzyme?

Back 12

proteolytic (digests proteins)

Front 13

Describe the action of trypsin.

Back 13

Endopeptidase active at basic amino acids.

Front 14

Describe the action of chymotrypsin.

Back 14

Endopeptidase active at aromatic amino acids.

Front 15

Describe the action of carboxypeptidase A & B.

Back 15

Exopeptidases active at C-term end; A active at aromatic and neutral amino acids and B active at basic amino acids

Front 16

When pancreatic cells release granules, do all have the same % of enzymes?

Back 16

YES!

Front 17

What type of pancreatic enzymes make up 75% of the pancreatic enzymes?

Back 17

Proteolytic (proteases including endopeptidases, and exopeptidases)

Front 18

Which is a more important method of pancreatic secretion control, neural or hormonal?

Back 18

Hormonal (secretin, CCK, and PP)

Front 19

What pH triggers the release of secretin from the mucosal cells?

Back 19

pH<4 in the duodenal lumen

Front 20

Which hormones/neural peptides bind to Acinar cells? via their receptors that are located there?

Back 20

1) VIP
2) GRP
3) CCK
4) ACh

Front 21

Which hormones/neural peptides bind to duct cell in the pancreas via their receptors that are located there?

Back 21

1) secretin
2) ACh

Front 22

What cells does secretin stimulate to secrete bicarbonate and water?

Back 22

1) pancreatic duct cells
2) duodenal glands
3) hepatocytes

Front 23

What receptors does CCK act on in the pancreas?

Back 23

CCK-A receptors

Front 24

What type of response does most of CCKs activity come from?

Back 24

long arc vago-vagal reflex

Front 25

When is PP secreted and what does it do?

Back 25

pancreatic polypeptide (PP) is an inhibitory regulator (inhibits vagal output from CNS)that is secreted during the meal and turns off the excitatory inputs on acinar cells
*proximal feedback loop

Front 26

What is PYY and when is it secreted?

Back 26

PYY is secreted from the ileum after a meal and inhibis gastric acid secretion, pancreatic enzyme secretion, and decreases transport
*distal feedback loop

Front 27

What are the 3 phases of postprandial pancreatic secretion?

Back 27

1) cephalic (25% of response)
2) gastric (10%)
3) intestinal (50-75%)

Front 28

Which pancreatic secretion phases are neurally regulated and which are hormonally regulated?

Back 28

1) neural - cephalic and gastric
2) hormonal - intestinal

Front 29

Explain stimulus secretion coupling of pancreatic acinar cell secretion.

Back 29

Receptors for two different things (ex. VIP and secretin) couple throuh the same pathway (ex. G protien) and potentiate each other.

Front 30

How much fluid is secreted by enterocytes/day?

Back 30

1000ml/day
(about 3000 ml total is secreted into the intestine, but much of that is from non-enterycte origin)

Front 31

Where is the oldest enterocyte located on a villus structure?

Back 31

at the tip of the villus where it will be sloughed off

Front 32

Explain how the enterocyte changes its function as it moves up the villus.

Back 32

crypt - net secretory cell
tip - net absorptive cell

Front 33

What ion is coupled with the secretion of water in an enterocyte?

Back 33

Cl-

(via the cystic fibrosis transmembrane regulator (CFTR) on the apical membrane)

Front 34

How does cholera toxin work?

Back 34

irreversibly activates G protein coupled to adenylate cyclase, increasing cAMP and keeping CFTR channel open (lose Cl-, Na+, and water)

Front 35

What makes up most of the colonic secretion?

Back 35

mucus

Front 36

What does interdigestive secretion do?

Back 36

gastric, bilary, and pancreatic fluid and enzymes is released periodically between meals to clear and clean the gut