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GB > 4. GIT Function 2 > Flashcards

4. GIT Function 2 Flashcards

1
Q

What factors inhibit acid secretion?

A

Enterogastric reflex

Presence of acid, fat and protein in duodenum

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2
Q

What is the enterogastric refex?

A

Distension of the duodenum results in reduced gastric motility and stomach emptying

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3
Q

What does presence of fatty acids and amino acids in the duodenum cause?

A

Secretion of cholecystokinin

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4
Q

What does presence of acid in the duodenum cause?

A

Secretion of secretin

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5
Q

What drugs can inhibit acid secretion?

A

Histamine H2 antagonists

Proton pump inhibitors

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6
Q

What usually happens when histamine acts of a H2 receptor?

A

Stimulates adenylate cyclase
Increases cAMP production
Increases H+ secretion

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7
Q

What is the effect of histamine H2 antagonists?

A

Reduces histamine and gastrin-stimulated acid secretion

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8
Q

Name a H2 antagonist?

A

Cimetidine

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9
Q

What is the action of proton pump inhibitors?

A

Irreversibly inhibits H+/K+ ATPase

Inhibits basal and stimulated acid secretion

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10
Q

Name a proton pump inhibitor

A

Omeprazole

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11
Q

What is CCK stimulated by?

A

Increased levels of fatty acids and amino acids in the duodenum
Activation of sensory afferents and effector nerves with the neurotransmitter CCK releasing peptide

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12
Q

What are the functions of CCK?

A

Inhibits gastric motility and acid secretion by activating CCKa receptors on D cells of pancreas and stomach to release somatostatin
Trophic to endocrine pancreas to increase secretion of pancreatic enzymes
Causes contraction of the gall bladder and relaxation of the sphincter of Oddi

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13
Q

What is secretin release stimulated by?

A

Presence of acid in duodenum

Activation of sensory afferents and effector nerves with neurotransmitter Secretin Releasing Peptide

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14
Q

What are the functions of secretin?

A

Inhibits gastric motility and acid secretion
Stimulates pancreatic duct cells to produce HCO3-
Stimulates liver to secrete bile
Inhibits gastric emptying

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15
Q

Which pancreatic cells produce enzymes?

A

Acinar cells

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16
Q

Which pancratic cells produce HCO3- and water?

A

Ductal epithelial cells

17
Q

What is the neural control of pancreatic secretions?

A

Vagus, enteric reflexes, ACh

18
Q

What is the hormonal control of pancreatic secretion?

A

Gastrin, CCK, secretin

19
Q

What are the 3 phases of pancreatic secretion?

A

Cephalic/reflex phase
Gastric phase
Intestinal phase

20
Q

What is the control of the cephalic phase?

A

ACh from Vagus

21
Q

What happens during the cephalic and gastric phases?

A

Release of a low volume of enzymes from acinar cells

Low volume aqueous NaHCO3- from ductal cells

22
Q

What is the control of the gastric phase?

A

Short reflexes stimulated by stretch and chemoreceptors

Gastrin (presence of peptides and AAs in chyme)

23
Q

What is the control of the intestinal phase?

A

Enterogastric reflexes
CCK (presence of FAs and AAs)
Secretin (acid)

24
Q

What happens during the intestinal phase?

A

Increased enzyme production in acinar cells
Secretion of HCO3- and water from epithelial duct cells
Increased cAMP (active anionic transport)
Acid is neutralised

25
Q

Describe the steps in bile secretion

A
  1. Vagus nerve stimulates bile production by the liver
  2. FAs and AAs in chyme stimulate CCK
    Acid stimulates secretin
  3. CCK causes contraction of the gall bladder
  4. Secretin causes secretion of bile from the liver
26
Q

Where are Brunner’s glands?

A

Submucosal layer of the duodenum

27
Q

What is the function of Brunner’s glands?

A

Secrete alkaline mucous to protect from acid

28
Q

What increases mucous secretion by Brunner’s glands?

A

Enteric reflex (distension)
Vagal stimulation
CCK and secretin

29
Q

Which hormones play a role in GI motility?

A

Motilin
Serotonin (5-HT)
Gastric Inhibitory Polypeptide
Somatostatin

30
Q

What is motilin?

A

Peptide from the mucosa of the upper GI

31
Q

What is the role of motilin?

A

Causes contractions of the stomach when fasting to signal hunger
Helps clear intestine of foreign bodies

32
Q

What is the migrating motor complex?

A

Waves of contraction of the small intestine every 1.5-2 hours in the absence of food

33
Q

What is 5-HT released from?

A

Enterochromaffin cells

34
Q

What does overstimulation of 5-HT3 receptors cause?

A

Nausea and vomiting

35
Q

Name a drug that blocks 5-HT3 receptors on sensory fibres

A

Ondansetron

36
Q

Where is GIP released from?

A

Duodenal mucosa

37
Q

What is GIP released in response to?

A

Food in intestine

38
Q

What is the function of GIP?

A

Inhibits acid secretion

Stimulates insulin production by pancreas

GB (15 decks)

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