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PHSL 233 > L11 > Flashcards

L11 Flashcards

1
Q

what do GI tract hormones and nerves signals promote

A

secretion of fluids and enzymes from epithelia and other associated organs

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2
Q

parietal epithelial secrete what

A

acidic fluid into the stomach

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3
Q

what does the pancreas secrete

A

digestive enzymes from the acinar cells

bicarbonate rich fluid from the duct cells

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4
Q

what cells would you find in the stomach

A

mucus cells

parietal cells

enterochromaffin like cells

G cells

D cells

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5
Q

what is the role of the different cells in the stomach

A

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

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6
Q

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

A

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

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7
Q

how is histamine released

A

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

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8
Q

where is histamine released from

A

ECL cells

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9
Q

what is the histamine signal transduction pathway

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

A

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

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10
Q

describe the ACh signal transduction pathway

A

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

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11
Q

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

A

acid reflux, gastric ulcers and gastric cancer

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12
Q

what is used to treat acid reflux

A

proton pump inhibitors

these bind to the H/K ATPase

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13
Q

what is helicobacter pylori

A

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

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14
Q

how does helicobacter pylori cause ulcers and cancer

A

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

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15
Q

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

A

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

B is right but for ACH not histamine

D should say exo

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16
Q

what do acinar cells secrete

A

digestive enzymes

17
Q

what are acinar cells stimulated by

A

CCK

18
Q

what do ductal cells secrete

A

bicarbonate rich fluid in response to secretin

19
Q

what stimulates ductal cells

A

secreatin

20
Q

what is pancreatic secretion important for

A

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

21
Q

what stimulates the release of CCK

A

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

22
Q

where is CCk released from

A

I cells in the small intestine

23
Q

how does CCK stimulate exocytosis of digestive enzymes

signal transduction pathway

A

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

24
Q

what are zymogen granules

A

These are vesicles that digestive enzymes are in.

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

25
Q

what causes secreatin to be released from intestinal cells

A

a decrease in pH in the duodenum

26
Q

what cells release secretin

A

intestinal S cells

27
Q

what is the signal transduction pathway for secreatin

A

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

28
Q

what does CFTR do in the ductal cell

A

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

29
Q

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

A

when the bicarbonate rich fluid is absent or reduced

this happens when CFTR is absent or dysfunctional

30
Q

what happens when you get reduced bicarbonate rich fluid

A

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)

PHSL 233 (31 decks)

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