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regulatory physiology and pharmacology > GI tract > Flashcards

GI tract Flashcards

1
Q

What is the pylorus?

A

regulates passage of chyme

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2
Q

What is chyme?

A

partially digested food and gastric juices formed in stomach

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3
Q

What is gastric emptying?

A

stomach moves chyme into small intestine via pyloric sphincter

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4
Q

How do fats affect gastric emptying?

A

they slow down gastric emptying due to releasing the hormone CKK

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5
Q

How do carbohydrates affect gastric emptying?

A

speed up emptying

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6
Q

What role does the vagus nerve play in gastric emptying?

A

regulates the contractions of the stomach and pyloric sphincter, influencing the rate of gastric emptying through parasympathetic control

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7
Q

How does the hormone gastrin influence gastric emptying?

A

increases gastric motility and promotes the emptying of the stomach by stimulating muscle contractions in the stomach.

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8
Q

How do hypertonic and acidic chyme affect gastric emptying?

A

slows down gastric emptying

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9
Q

What does hydrochloric acid (HCl) do in the stomach?

A

HCl, secreted by parietal cells, lowers stomach pH to activate pepsinogen into pepsin and helps kill bacteria.

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10
Q

What is the role of pepsinogen in digestion?

A

is secreted by chief cells
HCL converts pepsinogen to pepsin to break down proteins

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11
Q

What function does mucus serve in the stomach?

A

protects stomach lining for gastric juices and digestive enzymes

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12
Q

What is the function of gastric lipase?

A

is secreted by cheif cells
breaks down lipids

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13
Q

How does histamine influence stomach activity?

A

is secreted by enterochromaffin like cells
stimulates parental cells to secrete HCL

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14
Q

What does the hormone gastrin do?

A

secreted by G cells
stimulates parietal cells to release HCL
enhancing gastric motility

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15
Q

What is the role of bicarbonate in the stomach

A

neutralises acid in mucous layer

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16
Q

Which cells produce HCl in the stomach?

A

parietal cells

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17
Q

What enzyme is involved in HCl production inside parietal cells?

A

carbonic anahydrase converts C02 and water into carbonic acid which then dissociates into bicarbonate and hydrogen

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18
Q

How are hydrogen ions (H+) secreted into the stomach lumen?

A

primary active transport via H/K ATPase pump (proton pump)

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19
Q

What happens to bicarbonate (HCO3-) during HCl production?

A

exchanged for chloride at basolateral membrane

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20
Q

Which hormone stimulates HCl production and what pathway does it follow to do so?

A

gastrin
binds to CCK2
receptors on parietal cells
with subsequent activation
of PLC
PLC increases Calcium activating proton pump

21
Q

explain the pathway histamine follows to increase HCL production

A

upon stimulation by acetylcholine histamine binds to H2 receptors on basolateral membrane increasing adenyl cyclase activity therefore increasing cAMP and proton pump activity

22
Q

explain the pathway of Achieving effect on HCL production?

A

ACh is released by
parasympathetic cholinergic
neurons binding to
muscarinic (M3) ACh
receptors on parietal cells
with subsequent activation
of PLC therefore increasing proton pump activity

23
Q

What inhibits HCl secretion in the stomach?

A

somatostatin secured by D cells inhibits HCL secretion by suppressing gastrin release and directly inhibiting parietal cells

24
Q

What is the role of proton pump inhibitors (PPIs) in controlling HCl production?

A

blocks H/K ATPase pump (proton pump)

25
Q

which other lipid inhibits HCL secretion?
and the pathway it follows

A

Prostaglandins
bind to basolaterial membrane via EP3 receptors inhibiting adenyl cyclase activity

26
Q

What are the three phases of gastric secretion?

A

cephalic
gastric
intestinal

27
Q

What triggers the cephalic phase of gastric secretion?

A

thought , sight or smell of food
stimulates gastric secretion via vagus nerve

28
Q

How is the cephalic phase of gastric secretion regulated?

A

CNS sends signals from brain activating vagus nerve to stimulate parietal, chief, and G-cells in the stomach

29
Q

What initiates the gastric phase of secretion?

A

when food enters the stomach stretching stomach walls activating stretch receptors

30
Q

How is the gastric phase of secretion regulated?

A

gastrin release from G cells stimulating HCL secretion

31
Q

What triggers the intestinal phase of gastric secretion?

A

when chyme enters duodenum

32
Q

How is the intestinal phase regulated?

A

secretin and CCK
inhibit gastrin secretion and motility

33
Q

What is the main purpose of the intestinal phase?

A

controls rate of emptying

34
Q

How does acetylcholine enhance the activity of the H+/K+ ATPase?

A

is released from vagus nerve and binds M3 receptors on parietal cells increasing intracell Ca increasing proton pump activity

35
Q

Which second messenger system is activated by acetylcholine and gastrin to enhance H+/K+ ATPase activity?

A

increase intracellular Ca that activated H/K ATPase activity

36
Q

Which second messenger system is activated by histamine to enhance H+/K+ ATPase activity

A

activates cAMP

37
Q

What hormone is primarily responsible for stimulating the secretion of pancreatic enzymes and bile?

A

CCK

38
Q

Which hormone promotes the secretion of gastric acid in the stomach and is released when food enters the small intestine?

A

gastrin

39
Q

What hormone is released in response to low pH in the small intestine and stimulates the secretion of bicarbonate from the pancreas?

A

secretin

40
Q

How do hormones like CCK and secretin affect the motility of the small intestine?

A

slow down motility

41
Q

What effect does CCK have on gallbladder function?

A

stimulates contraction of gallbladder to eject bile into duodenum

42
Q

what type of cells of duo and jej secrete GIP ?
what does it stimulate and inhibit

A

K cells
stimulates released of insulin from pancreatic B cells
inhibits gastric emptying

43
Q

what type of cells secretes GLP-1(small intestine)
GLP-1 stimulates =
GLP-1 inhibits=
GLP-1 decreases=

A

L cells
insulin secretion
glucagon secretion from pancreatic a cells
gastric emptying and appetite

44
Q

what type of cells of duo and jej secrete motilin
and when are they secreted

A

M cells
during fasting

45
Q

Ghrelin is secreted from ___ cells and stimulates ____

A

Gr appetite

46
Q

How does the pancreas contribute to digestion via its exocrine function?

A

secretes digestive enzymes into small intestine

47
Q

Which hormones does the pancreas secrete to regulate blood sugar levels?

A

insulin and glucagon

48
Q

role of goblet cells

A

create mucus layer

49
Q

What are the two main functions of the pancreas in relation to the GI tract?

A

endocrine = hormonal
exocrine= digestive enzymes

regulatory physiology and pharmacology (20 decks)

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