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Secretion of ions and enzymes in the GI tract Flashcards

1
Q

What does the control of salivary secretion depend on?

A

Nervous system

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2
Q

What is tastebuds and mechanoreceptors activated by?

A

Food

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3
Q

Where is sensory information sent to, what type of reflex?

A

Salivary nucleus in medulla of brain

Unconditional reflex

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4
Q

What is a conditional reflex of the salivary nucleus?

A

sensory input to brain e.g sight, smell of food

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5
Q

How does saliva secretion receive impulses?

A

via autonomic nerve

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6
Q

What autonomic nerves create saliva secretion?

A

parasympathetic, cranial nerves 7 & 9

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7
Q

Where does impulses for saliva secretion go to?

A

salivary glands

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8
Q

What does the salivary glands do?

A

Increase secretion of fluid/enzymes/mucins and dilate blood vessels

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9
Q

What is the PH of saliva? (low flow rate)

A

6.2

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10
Q

What is the PH of saliva, high flow rate?

A

8.0

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11
Q

Where does secretions of primary saliva occur?

A

In acinus of a salivary gland

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12
Q

Where does secondary modification of saliva occur?

A

in the duct

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13
Q

Where does mucus in the stomach occur from?

A

Surface epithelial and mucus neck cells - glycoprotein forms gel with water - protective layer over epithelium

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14
Q

Where does the bicarbonate secretions arise from in the stomach?

A

surface epithelial cells - trapped in mucus layer, protective against acid

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15
Q

Where does hydrochloric acid arise from in the stomach?

A

Parietal cells

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16
Q

What is the intrinsic factors of gastric secretions occur from?

A

parietal cells - protection of vitamin b12

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17
Q

Where do pepsinogens arise from?

A

Chief cells - commences protein digestion

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18
Q

What are pepsins?

A

Endopeptidase enzymes

19
Q

What do pepsins do?

A

Hydrolyse specific peptide bonds within a protein chain

20
Q

What do exopeptidases do?

A

Hydrolyse terminal peptide bonds and generate free AA

21
Q

What is the function of gastric acids?

A

activate pepsinogens, maintains pepsin activity, bacteriocidal, disrupts CT proteins, dissolves matter in food

22
Q

What are 3 important factors of stimulating gastric secretion?

A

Acetylcholine
Gastrin
Histamine

23
Q

What does acetylcholine do to stimulate gastric secretion?

A

neurotransmitter release from vagus nerve and local intrinsic nerves

24
Q

What does Gastrin do?

A

Hormone released from G cells of antral mucosa by acetylcholine, stretch, proteins, circulates in bloodstream to parietal and secretory cells

25
Q

What does Histamine do?

A

Local hormone release from cells close to parietal cells by gastrin and ACh - active to give strong secretory response - synergistic

26
Q

What is phase 1?

A

Cephalic phase - head

27
Q

What is phase 1 triggered by?

A

thought, smells, sight, taste

28
Q

What is phase 1 controlled by?

A

Nervous mechanisms - impulses from CNS via vagus nerve - release of acid and pepsin, small release of gastrin from antral g cells

29
Q

Why is phase 1 important?

A

Intact vagus nerve releases ACh as neurotransmitter

30
Q

What is phase 2 ?

A

Gastric phase - stomach

31
Q

What is phase 2 triggered by?

A

distension of stomach by food - action of food components e.g peptides, caffeine, alchohol

32
Q

What is phase 2 controlled by?

A

Hormonal mechanisms - release gastrin from g cells of antrum, circulates to glands in fundus increase acid and pepsin secretion

33
Q

What is important in phase 2?

A

Hormone gastrin is important

34
Q

What is phase 3?

A

Intestinal phase

35
Q

What is phase 3 triggered by?

A

emptying of stomach contents into duodenum (fats, acid, peptides) , low PH in gastric antrum

36
Q

What is phase 3 controlled by?

A

Release of hormones from duodenal mucosa which inhibit gastric secretion (secretin, cholecystokinin) - short local and long cns nervous reflexes inhibit gastric secretions

37
Q

Why is phase 3 important?

A

Nerves and hormones

38
Q

What is peptic ulcer disease (PUD)?

A

protective mechanisms normally operating in epithelium of stomach fail, and epithelial/subepithelial cells become inflamed and damaged by acid and pepsins

39
Q

What are symptons of PUD?

A

Painful, troublesome, common and dangerous (haemorrhage)

40
Q

What are common causes of PUD?

A

Too much acid/pepsin/histamine
Steroidal and nonsteroidal anti-inflam drugs
Helicobacter pylori infection

41
Q

What is treatment for PUD?

A

eradicate infection with antibiotics
change medication
block acid secretion by using proton pump inhibitors (losec, zantac)

42
Q

What can peptic ulcers occur?

A

Oesophagus, stomach, duodenal cap

43
Q

What is zollinger ellison syndrome?

A

levels of gastrin raised in secretory gastrinomas - excess basal and stimulated acid and pepsin secretion, hypertrophy of gastric mucosa

NE (17 decks)

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