L11

Question 1

what do GI tract hormones and nerves signals promote

Answer 1

secretion of fluids and enzymes from epithelia and other associated organs

Question 2

parietal epithelial secrete what

Answer 2

acidic fluid into the stomach

Question 3

what does the pancreas secrete

Answer 3

digestive enzymes from the acinar cells

bicarbonate rich fluid from the duct cells

Question 4

what cells would you find in the stomach

Answer 4

mucus cells

parietal cells

enterochromaffin like cells

G cells

D cells

Question 5

what is the role of the different cells in the stomach

Answer 5

mucus cells - protection

parietal cells - secrete acid

enterochromaffin like cells - activate the parietal cells

don’t need to know what the G cells and D cells do

Question 6

what are the advantages of multiple signals, using different pathways, stimulating the same physiological outcome

Answer 6

We have 2 (there’s more than 2 but we only learn 2) different pathways so that we get more acid secreted. and if one isn’t working then we still get acid secreted

Question 7

how is histamine released

Answer 7

the vagal nerve (in the brain stem) stimulates the enteric nerve which stimulates endochromiffin like cells (ECL cells)

Question 8

where is histamine released from

Answer 8

ECL cells

Question 9

what is the histamine signal transduction pathway

not the pathway of histamine release but the pathway that histamine causes

Answer 9

vagal nerve stimulates enteric nerve which stimulates ECL cells

ECL cells release histamine

it binds to the H2 receptor (which is GPCR)

adenylyl cyclase catalyzes ATP –> cAMP which activates PKA

PKA phosphorylates the H/K pump which causes it to be endocytosed into the apical membrane

H+ is pumped out of the cell as well as Cl through CFTR to create HCL in the stomach

Question 10

describe the ACh signal transduction pathway

Answer 10

the vagal nerve stimulates the enteric nerve which releases ACh

ACh binds to the M3 receptor (muscarinic receptor) which is a GPCR. this convertes GTP –> GDP

this activates phospholipase C which breaks down PIP2 into IP3 and DAG

DAG activates PKC

IP3 binds to its receptor on the ER. increased cytoplasmic Ca levels

together this leads to the phosphorylation and activation of the H/K pump causing to it be exocytosed to the apical membrane causing HCL to be secreted into the lumen of the stomach

Question 11

what happens when something in the acid production pathway don’t go right

Answer 11

acid reflux, gastric ulcers and gastric cancer

Question 12

what is used to treat acid reflux

Answer 12

proton pump inhibitors

these bind to the H/K ATPase

Question 13

what is helicobacter pylori

Answer 13

it is a bacteria which inhibits acid secretion and promotes gastric ulcer formation eventually leading to gastric cancer

Question 14

how does helicobacter pylori cause ulcers and cancer

Answer 14

damages the epithelial meaning that the acid is able to leak through the epithelium leading to gastric ulcers and stomach cancer

Question 15

For successful stimulation of hydrochloric acid secretion from stomach parietal epithelial cells:

A. Histamine is released from enterochromaffin-like (ECL) cells.

B. Histamine stimulates conversion of phosphatidyl inositol bisphosphate (PIP2) to diacylglycerol (DAG) and inositol triphosphate (IP3).

C. Histamine activates a GPCR, while acetylcholine does not

D. Vesicular H+/K+ATPase is endocytosed from the apical
membrane

Answer 15

A. Histamine is released from enterochromaffin-like (ECL) cells.

B is right but for ACH not histamine

D should say exo

Question 16

what do acinar cells secrete

Answer 16

digestive enzymes

Question 17

what are acinar cells stimulated by

Answer 17

CCK

Question 18

what do ductal cells secrete

Answer 18

bicarbonate rich fluid in response to secretin

Question 19

what stimulates ductal cells

Answer 19

secreatin

Question 20

what is pancreatic secretion important for

Answer 20

Important for regulating sugar levels but it is also important for digestion

Question 21

what stimulates the release of CCK

Answer 21

fatty acids in digested food when it is passes into the intestine

Question 22

where is CCk released from

Answer 22

I cells in the small intestine

Question 23

how does CCK stimulate exocytosis of digestive enzymes

signal transduction pathway

Answer 23

CCK binds to its CCK1 receptor on the basolateral membrane of the pancreatic acinar cells

this is a GPCR which activates PLC

PLC breaks down PIP2 into IP3 and DAG

IP3 and DAG do their thang which leads to the exocytosis of zymogen granules

Question 24

what are zymogen granules

Answer 24

These are vesicles that digestive enzymes are in.

They are in special things so they don’t start digesting the inside of the cell

Question 25

what causes secreatin to be released from intestinal cells

Answer 25

a decrease in pH in the duodenum

Question 26

what cells release secretin

Answer 26

intestinal S cells

Question 27

what is the signal transduction pathway for secreatin

Answer 27

it binds to it S1 receptor on the pancreatic membrane of the ductal cells this is a GPCR therefore it activates adenylyl cyclase which breaks down ATP --> cAMP cAMP activates PKA which phosphorylates CFTR CFTR is then exocytose into the apical membrane of the pancreatic ductal cells

Question 28

what does CFTR do in the ductal cell

Answer 28

it pumps out bicarbonate to neutralize the acid as it comes passed. it also acts as a carrier for the digestive enzymes to help them get the the small intestine

Question 29

when does cystic fibrosis happen (in terms of its effect on the digestive system)

Answer 29

when the bicarbonate rich fluid is absent or reduced this happens when CFTR is absent or dysfunctional

Question 30

what happens when you get reduced bicarbonate rich fluid

Answer 30

reduced fluid in the duct means that you are unable to move those digestive enzymes down the pancreatic duct (no digestion = malnourished) it also means that there will be no neutralisation of the small intestine (stomach ulcers which then could progress into stomach cancer)