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Year 2- GIT > Gastric Secretion > Flashcards

Gastric Secretion Flashcards

(90 cards)

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1
Q

What is the main function of the fundus?

A

Storage

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2
Q

List the secretions of the body of the stomach

A

HCL
Mucus
Pepsinogen
Intrinsic factor

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3
Q

What is the main function of the antrum of the stomach?

A

Mixing/grinding the food before transferring it down to the small intestine

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4
Q

What do G cells found in the antrum release?

A

Gastrin (hormone)

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5
Q

What does mucin form?

A

Mucus

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6
Q

What do mucous neck cells secrete?

A

Mucous

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7
Q

What do chief cells secrete?

A

Pepsinogen

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8
Q

Why do the cells secrete pepsinogen rather than pepsin?

A

Pepsin breaks down proteins so would break down the cells which produces the pepsin

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9
Q

What do the parietal cells secrete?

A

Hydrochloric acid
Intrinsic factor

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10
Q

What can form in the stomach from carbon dioxide and water?

A

Carbonic acid

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11
Q

Which enzyme catalyses the reaction of carbon dioxide and water into carbonic acid?

A

Carbonic Anhydrase

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12
Q

What can carbonic acid dissociate into?

A

One molecule of carbonic acid can turn into one proton and HCO3

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13
Q

Name the pump which can pump protons into the stomach lumen.

A

Proton potassium pump

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14
Q

What is the ratio of the proton postassium pump?

A

Pumps one proton out and one potassium in

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15
Q

Name two drugs which inhibit the proton potassium pump.

A

Omeprazole
Lansoprazole,

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16
Q

When a proton is pumped out, will the pH of the stomach lumen become more acidic or alkaline?

A

Acidic

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17
Q

How will pumping of bicarbonate into the blood affect the pH of blood?

A

Will make blood more alkaline

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18
Q

Describe what is meant by postprandial alkalisation.

A

pH of the blood becomes slightly more alkaline, usually happens just after eating for a short period of time

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19
Q

In exchange for bicarbonate going out of the cell, what comes into the cell?

A

Chlorine

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20
Q

What forms when chlorine goes into the stomach lumen?

A

Hydrochloric acid HCl

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21
Q

What is the pH of the stomach?

A

Approx 1.5

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22
Q

What happens in terms of osmotic gradients when chlorine and protons move towards the stomach lumen?

A

Forces the water in blood to move through tight junctions to go into the stomach of the lumen.

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23
Q

What role does HCl have?

A

Plays an important role in the sterilisation of food.

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24
Q

When is the proton potassium pump activated?

A

When it is phosphorylated- it has to have a phosphate group attached

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25
Which enzyme is responsible for phosphorylation?
Kinase
26
What will happen if there is inhibition of kinase in terms of hydrochloric acid secretion?
Decreased hydrochloric acid secretion
27
Which cells produce gastrin?
G cells
28
Where are G cells found?
Gastric antrum of the stomach
29
Which receptor does gastrin work on?
CCK-B receptor
30
What happens when gastrin works on the CCK-B receptor?
Increased release of calcium
31
Which enzyme can calcium activate?
Protein kinase C
32
What happens when protein kinase C is activated?
More protons are released
33
What is meant by paracrine secretions?
Secreted into a neighbouring cell
34
Name the two receptors that histamine can act on
H1 and H2
35
Which histamine receptor is more allergy based?
H1
36
What is the function of H2?
Secretion of gastric juice.
37
Which receptor is the H2 receptor coupled with?
G protein S coupled receptor (GS receptor)
38
What does the GS receptor activate?
Adenylyl cyclase.
39
What does adenylyl cyclase do?
Increasers the rate of conversion of ATP to cAMP
40
Which enzyme does cAMP activate?
Protein kinase A
41
What happens if you have the activation of protein kinases?
Phosphorylates the pump to increase release of HCl or protons
42
Which receptor does acetylcholine work on?
Muscarinic receptors known as M3
43
Is the release of acetylcholine based on the activation of sympathetic NS or the parasympathetic NS?
Parasympathetic NS
44
What will the activation of M3 do?
Increase calcium which will activate protein kinase C. This will phosphorylate the pump and increase proton pumping from the parietal cells to the stomach lumen. -this is the same as gastrin, so we can say the effects of gastrin and acetylcholine are the same :)
45
Which receptor do prostaglandins work on?
EP3
46
What happens when the EP3 receptor is activated?
It will activate G inhibitory protein (GI protein)
47
What does GI protein do?
Inhibits the conversion of ATP to cAMP which decreases the activation of protein kinase A. In turn, this decreases the phosphorylation of the pump and decreases the proton pumping, inhibiting the release of HCl. ->I know this is a lot but read through and try and make the links. The recorded lecture may be helpful when going over all of this :)
48
Name the three mechanisms which control the secretion of gastric acid.
Neurocrine Endocrine Paracrine
49
Give an example of a neurocrine mechanisms which controls the secretion of gastric acid.
Acetylcholine
50
Give an example of a endocrine mechanisms which controls the secretion of gastric acid.
Gastrine
51
Give an example of a paracrine mechanisms which controls the secretion of gastric acid.
Histamine Prostaglandins
52
Name the three stimulants for the secretion of gastric acid.
Acetylcholine Gastrin Histamine
53
Name the inhabitant for the secretion of gastric acid.
Prostaglandin
54
What can stimulate the cephalic stage gastric acid secretion?
Sight/ smell/ taste of food
55
Which nerve is related to the cephalic stage of gastric acid secreation?
Vagus nerve
56
What will activation of the vagus nerve do?
Increase the release of acetylcholine Increase the release of gastrin from G cells
57
Which cells get activated when there is gastrin and acetylcholine in the stomach?
ECL cells
58
What do ECL cells release?
Histamine
59
The cephalic stage occurs before eating food. When does the gastric stage occur?
When there is distension of the stomach due to the arrival of food
60
Which reflexes are activated when the food arrives from the oesophagus into the stomach?
Vagal/enteric reflexes
61
What happens due to the vagal/enteric reflexes?
Release of acetylocholine
62
What do the peptides found in the lumen activate?
G cells, increasing the production of HCl
63
Why do we have the cephalic stage?
Important for the sterilisation of food as acid will be produced before the food even enters the stomach
64
How would the cephalic stage be inhibited?
Stopping thinking or eating food as will decrease vagal activity
65
How would the gastric stage be inhibited?
More HCl will decrease the pH which in turn decreases the release of gastrin.
66
Name the type of mechanism which occurs when despite the fact that gastrin increases HCl production, HCl lowers pH which in turn reduces the release of gastrin.
Negative feedback ->sorry if I didn't word that very well but hopefully you get what I mean :)
67
What is meant by the intestinal stage?
When the food moves from the stomach to the duodenum
68
What is the usual pH of the intestine?
Neutral or slightly alkaline
69
If acidic content comes from the stomach to the intestine, what is this called?
Splanchnic reflex
70
What will a splanchnic reflex do?
Inhibit the gastric acid secretion
71
What do S cells in the duodenum release?
Secretin horomone
72
What what the secretin hormone do?
Decrease gastrin release in the stomach
73
What will having fats or carbs in the duodenum trigger the release of?
Gastric Inhibitory Peptide
74
What does gastric inhibitory peptide do?
Decreases gastric secretion which in turn decreases HCl secretion
75
What are enterogastrones?
A group of hormones which are released from cells in the duodenum
76
Name some of the hormones which are enterogastrones.
Secretin Gastric Inhibitory Peptide CCK (cholecystokinin)
77
When are enterogastrones released?
In response to acid, hypertonic situations, fatty acids or monoglycerides in the duodenum
78
RECAP- what are triglycerides degraded into?
Fatty acids and monoglycerides
79
How do enterogastrones prevent the duodenum from having a buildup of acid?
Inhibit gastric acid secretion Reduce gastric emptying
80
What is meant by zymogen?
An inactive enzyme
81
Give an example of an inactive enzyme
Pepsinogen
82
When does pepsinogen get converted into pepsin?
When there is a low pH of the stomach lumen
83
Is the conversion of pepsinogen into pepsin reversible?
Yes
84
Where is pepsinogen stored?
Chief cells ->think about it, it's secreted from chief cells so makes sense for it to be stored there
85
At what pH will pepsins become inactivated?
Neutral pH
86
Which cells produce gastric mucus?
Surface epithelial cells and mucus neck cells
87
What is the role of gastric mucus?
Protects the stomach wall from HCl and hydrolytic enzymes
88
What is the pH of gastric mucus and why is this important?
Neutral- this is important because it protects the wall against gastric acid erosion and pepsin digestion.
89
What does gastric mucus contain which helps to neutralise HCl?
Bicarbonate
90

Year 2- GIT (37 decks)

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