Secretion of ions and enzymes in the GI tract

Question 1

What does the control of salivary secretion depend on?

Answer 1

Nervous system

Question 2

What is tastebuds and mechanoreceptors activated by?

Answer 2

Food

Question 3

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

Answer 3

Salivary nucleus in medulla of brain

Unconditional reflex

Question 4

What is a conditional reflex of the salivary nucleus?

Answer 4

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

Question 5

How does saliva secretion receive impulses?

Answer 5

via autonomic nerve

Question 6

What autonomic nerves create saliva secretion?

Answer 6

parasympathetic, cranial nerves 7 & 9

Question 7

Where does impulses for saliva secretion go to?

Answer 7

salivary glands

Question 8

What does the salivary glands do?

Answer 8

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

Question 9

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

Answer 9

6.2

Question 10

What is the PH of saliva, high flow rate?

Answer 10

8.0

Question 11

Where does secretions of primary saliva occur?

Answer 11

In acinus of a salivary gland

Question 12

Where does secondary modification of saliva occur?

Answer 12

in the duct

Question 13

Where does mucus in the stomach occur from?

Answer 13

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

Question 14

Where does the bicarbonate secretions arise from in the stomach?

Answer 14

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

Question 15

Where does hydrochloric acid arise from in the stomach?

Answer 15

Parietal cells

Question 16

What is the intrinsic factors of gastric secretions occur from?

Answer 16

parietal cells - protection of vitamin b12

Question 17

Where do pepsinogens arise from?

Answer 17

Chief cells - commences protein digestion

Question 18

What are pepsins?

Answer 18

Endopeptidase enzymes

Question 19

What do pepsins do?

Answer 19

Hydrolyse specific peptide bonds within a protein chain

Question 20

What do exopeptidases do?

Answer 20

Hydrolyse terminal peptide bonds and generate free AA

Question 21

What is the function of gastric acids?

Answer 21

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

Question 22

What are 3 important factors of stimulating gastric secretion?

Answer 22

Acetylcholine
Gastrin
Histamine

Question 23

What does acetylcholine do to stimulate gastric secretion?

Answer 23

neurotransmitter release from vagus nerve and local intrinsic nerves

Question 24

What does Gastrin do?

Answer 24

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

Question 25

What does Histamine do?

Answer 25

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

Question 26

What is phase 1?

Answer 26

Cephalic phase - head

Question 27

What is phase 1 triggered by?

Answer 27

thought, smells, sight, taste

Question 28

What is phase 1 controlled by?

Answer 28

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

Question 29

Why is phase 1 important?

Answer 29

Intact vagus nerve releases ACh as neurotransmitter

Question 30

What is phase 2 ?

Answer 30

Gastric phase - stomach

Question 31

What is phase 2 triggered by?

Answer 31

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

Question 32

What is phase 2 controlled by?

Answer 32

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

Question 33

What is important in phase 2?

Answer 33

Hormone gastrin is important

Question 34

What is phase 3?

Answer 34

Intestinal phase

Question 35

What is phase 3 triggered by?

Answer 35

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

Question 36

What is phase 3 controlled by?

Answer 36

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

Question 37

Why is phase 3 important?

Answer 37

Nerves and hormones

Question 38

What is peptic ulcer disease (PUD)?

Answer 38

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

Question 39

What are symptons of PUD?

Answer 39

Painful, troublesome, common and dangerous (haemorrhage)

Question 40

What are common causes of PUD?

Answer 40

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

Question 41

What is treatment for PUD?

Answer 41

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

Question 42

What can peptic ulcers occur?

Answer 42

Oesophagus, stomach, duodenal cap

Question 43

What is zollinger ellison syndrome?

Answer 43

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