Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

imed3004 > Physiology: Stomach acid secretion (RW) > Flashcards

Physiology: Stomach acid secretion (RW) Flashcards

1
Q

What are the 4 regions of the body? What happens in these locations?

A

Cardia: lacks musculature because it needs to remain static

Fundus: Acts as extra reservoir

Corpus: Produce acid (contains parietal cells)

Antrum: Contains pyloric sphincter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What glands are present in the stomach that are important for digestion?

A

3 types of exocrine glands:

Mucous neck cells (mucus)

Parietal cells (Produce intrinsic factor and HCl)

Chief cells (Produce pepsinogen and gastric lipase)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What endocrine cells are present in the GIT mucosa?

A

G cells which secrete gastrin and D cells which secrete somatostatin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does gastrin regulate?

A

Stomach acid secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is secreted by the antrum?

A

Mucus

Pepsinogen

Gastrin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does the antrum do besides secretion?

A

It is the mixer of the stomach.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does the stomach respond to food entry?

A

Swallow relaxes the lower oesophageal sphincter

Stomach receptive relaxation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How does the stomach relax in response to food entry?

A

Intrinsic reflex and vago-vagal response

Little change in pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the vago-vagal response?

A

Stretch receptors on stomach result in NO and VIP release in the stomach relaxing the stomach.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is antral systole?

A

Grinding via smooth muscle contractions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does duodenal distension do to antral activity?

A

Duodenal distension (+acid) inhibits antral motor activity. This is to prevent entry of more food into duodenum.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does CCK/Secretin activity do to pyloric sphincter?

A

Stimulates contraction to prevent regurgitation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does smelling food affect gastric emptying?

A

It increases rate of gastric emptying.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What factors affecting the duodenum delay gastric emptying?

A

Increased acidity

Increased amount of fat

Increased amount of amino acids

Hypertonicity

Distension

Hyperosmotic conditions decrease emptying rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What hormones increase in concentration in response to need for increased gastric emptying?

A

Endogastrones such as CCK GIP and Secretin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What cells are found in gastric pits?

A

Mucous cell

Mucous neck cell (secretes mucous to protect the deeper cells)

Parietal cell

Chief cell

D and G cells (secrete gastrin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What do parietal cells do?

A

Secrete stomach acid and intrinsic factor which is essential for vitamin B12 absorption.

This activates pepsin and kills bacteria.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What do enterochromaffin like cells produce?

A

Histamine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What stimulates enterochromaffin like cells to produce their hormones?

A

Acetylcholine and gastrin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does histamine do?

A

Stimulates gastric acid secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What stimulates mucous neck cells to release mucous?

A

Tonically secreted with irritation of the mucosa.

22
Q

What do mucous neck cells produce?

A

Mucous and bicarbonate providing physical barrier between lumen and epithelium and buffrs acid to prevent damage to epithelium.

23
Q

What stimulates parietal cells to produce HCl and intrinsic factor?

A

Acetylcholine, histamine, and gastrin

24
Q

What stimulates chief cells to release pepsin(ogen) and gastric lipase?

A

Acetylcholine, and acid secretion

25
Q

What do chief cells do?

A

They produce pepsin(ogen) and gastric lipase

26
Q

What do D cells do?

A

Produce somatostatin which inhibits gastric acid secretion

27
Q

What stimulates D cell activity?

A

Acetylcholine, peptides, and amino acids

28
Q

What do G cells do?

A

Produce gastrin which stimulates gastric acid secretion

29
Q

What stimulates G cell activity?

A

Acetylcholine, peptides, and amino acids.

30
Q

What cells are present in the antrum?

A

Only mucous surface cells, mucous neck cells, and endocrine cells (G and D cells).

31
Q

What drives acid secretion?

A

Maximal [H+] in gastric secretions is driven by H+/K+ ATPases which actively transport H+ out in exchange for potassium with the help of ATP

32
Q

How are H+/K+ ATPases switched on and off?

A

They are always on if they are on the membrane. They get switched off by endocytosis and putting them in vesicles within the cell. They then get exocytosed and added back onto membrane in response to chemical messages.

33
Q

What do ‘-prazoles’ do?

A

They inhibit proton pumps.

34
Q

How is acid made prior to secretion?

A

Parietal cells use CO2 to reduce OH from H2O resulting in free H+ to be pumped out of the membrane via the H+/K+ - ATPase

K+ concentration gradients is produced by a proton pump on the basolateral membrane which pumps potassium into the cell in exchange for sodium. This potassium then diffuses out on the apical side.

Cl is pumped out of apical side to balance out the H+

H2O flows into the lumen of the stomach via osmosis.

35
Q

What does the resulting alkalinity from loss of H+ to the stomach acid do?

A

It creates an alkaline tide in the bloodstream which can be used for other processes.

36
Q

What receptors do ACh, Histamine, and Gastrin bind to? What secondary messenger is produced in response?

A

ACh to M3 muscarinic receptor: Upregulates Ca2+

Histamine to H2 receptor: Upregulates cAMP

Gastrin to CCK-B receptor: Upregulates Ca2+

37
Q

How does vagal stimulation result in gastrin secretion?

A

Vagal stimulation results in release of gastrin-releasing peptide.

38
Q

What are the stimulants of gastrin secretion?

A

Vagal stimulation -> Gastrin-releasing peptide

Small proteins and protein digestion products in gastric antrum

Antral distension

Inhibition: Acid, somatostatin, bloodborne secretin, GIP, VIP, glucagon, calcitonin

39
Q

What does gastrin do?

A

Stimulate acid secretion from parietal cells

Release histamine from ECL cells

Release pepsinogen from chief cells

40
Q

What type of hormone is gastrin?

A

Peptide hormone.

41
Q

What do D cells do?

A

They produce somatostatin

42
Q

What stimulates release of somatostatin?

A

D cells have pH sensitive receptors which release in response to <4 pH as well as CCK and secretin.

43
Q

Where are somatostatin granules stored?

A

Non-luminal cell processes up to 40 microns long

44
Q

What does lumokine refer to?

A

Produced and released into the lumen to act on cells from apical side.

45
Q

When is there a spike in acid production by parietal cells?

A

When ECL cells are acted on by gastrin to produce histamine which results in sharp increase in acid secretion by parietal cells.

46
Q

What local negative feedback acts on parietal cells?

A

Somatostatin is produced by increased acid in antrum.

Food in the stomach buffers acid preventing negative feedback.

47
Q

What does intestinal phase do for stomach?

A

Largely inhibitory: Nervous reflexes (Duodenum -> Antrum) and hormones released from duodenal mucosa in contact with food..

CCK released from duodenum wall and secretin from duodenal mucosa in contact with acid.

48
Q

What is pepsin/pepsinogen released in response to?

A

Same exact stimuli as gastric acid

49
Q

Where does bicarbonate in mucous come from?

A

Mucous contains bicarbonate from bloodstream (Using alkaline tide) to neutralize acid that passes through the mucous)

50
Q

What stabilizes mucous layer?

A

Mucins plus trefoil factor (Peptides) stabilise the mucous layer.

51
Q

What does mucous layer do to protect stomach lining?

A

Contains bicarb which neutralizes acid on its way.

Alkaline layer also inactivates pepsin

Prostaglandins are important for barrier integrity (hence NSAIDs and aspirin can inhibit COX-1 PG formation and this would result in mucosal damage.

imed3004 (50 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions