Gastrointestinal Physiology (con'd)

Question 1

What is the cephalic phase?

Answer 1

Vagus nerve (thinking about, smelling, or tasting food) stimulates the ENS to produce acid, gastrin and HCl, and Histamine
this occurs before you eat
Prepartory process

Question 2

what is the negative feed back mechanism if pH is too low?

Answer 2

causes D cells to release somatostatin which inhibit G cells, ECL cells, and parietal cells

Question 3

what is the gastric phase?

Answer 3

when food is present in stomach triggers gastointestinal reflex. Baroreceptors detect enlargment of stomach and chemoreceptors respond to food (sent via vagus nerve), stimulating goblet cells, parietal cells, G cells and chief cells

Question 4

what happens to food when the pH gets too low?

Answer 4

movement of food slows down

Question 5

what is the intestinal phase?

Answer 5

signal coming from the intestine to prepare for incoming food

Question 6

what is the enterogastric reflex?

Answer 6

signal from intestine snt to stomach. chemoreceptors detect pH and good contents, causing hormone secretin to be secreted.

Question 7

what does secretin do?

Answer 7

inhibits gastric function via parietal/chief cell

Question 8

what other molecules inhibit stomach function which is stronger

Answer 8

gastric inhibitory peptide (GIP) - stronger

cholecystokinin

Question 9

what does the D cell do?

Answer 9

secretes somatostatin in response to H+ which acts on G cell, parietal cell, and ECL cells

Question 10

what are the two classes of drugs that prevent acid secretion? which is irreversible?

Answer 10

H2 blockers

proton pump inhibitors (irreversible)

Question 11

why are NSDAIDs bad for the stomach?

Answer 11

prevents prostaglandin synthesis

Question 12

why are NSDAIDs bad for the stomach?

Answer 12

prevents prostaglandin synthesis which regulated gastric secretion

Question 13

what are two 2 COX enzymes?

Answer 13

constitutive COX 1

inducible cox 2

Question 14

what is the difference between cox 1 and cox 2?

Answer 14

cox 1 - works all the time and makes a low, protective dose of PG
cox 2 - makes no PG when turned off, but makes a lot when turned on (pro inflammatory)

Question 15

what is the difference between 1st and 2nd generation NSAIDs?

Answer 15

1st - non specific (block both cox 1 and cox2)

snd - block cox 2 only

Question 16

what is a downside to 2nd generation NSAIDs?

Answer 16

can cause heart attack

Question 17

what are NO-NSAIDs?

Answer 17

Nitric oxide NSAIDs (modified NSAID)
have nonselective COX inhibition and NO release causes vasodilation (protective)
CINODs are also non-specific

Question 18

what is the difference between endocrine and exocrine pancreas?

Answer 18

endo - pancreatic islets

exo - pancreatic duct

Question 19

how much pancreatic juice is secreted a day?

Answer 19

1500ml/day

Question 20

what are the two components of pancreatic juice?

Answer 20

1) aqueous which has Na-HCO3 solution (buffer stomach pH)

2) enzyme - proteolytic enzymes (zymogens), pancreatic amylase/lipases

Question 21

what 3 things control pancreatic secretion?

Answer 21

vagus nerve
cholecystokinin
secretin

Question 22

how does the vagus nerve control pancreatic secretion?

Answer 22

activates Ach? (parasym) which is excitatory and promote excretion or NE (sym) which inhibits secretion

Question 23

how does cholecystokinin control pancreatic secretion?

Answer 23

detects lipids and has positive effect on pancreas but negative effect on stomach
also decreases gastric emptying

Question 24

how does cholecystokinin control pancreatic secretion?

Answer 24

detects lipids and has positive effect on pancreas but negative effect on stomach
also decreases gastric emptying

Question 25

how does secretin affect pancreatic secretion?

Answer 25

when acidic contents reach the stomach, it causes secretin release which acts on pancreas to increase aqueous secretion also decreases gastric emptying

Question 26

what is the function of the liver?

Answer 26

continually produce bile

Question 27

what is the function of bile?

Answer 27

neutralization via HCO3 | emulsification via bile salts to solubilize oils

Question 28

what 3 things control gall bladder emptying?

Answer 28

cholecystokinin (gall bladder contraction and relaxation of sphincter of Oddi) parasym Ach (weak) secretin

Question 29

when is cholecystokinin (CCK) released?

Answer 29

when fats are released into duodenum

Question 30

what are crypts of lieberkuhn?

Answer 30

look similar to gastric glands in stomach but are in small intestine they secrete by young cells at bottom of crypt

Question 31

what is the function of the villi?

Answer 31

absorption site

Question 32

what are the 2 kinds of secretion from the small intestine?

Answer 32

``` watery secretion (containing electrolytes) mucoid secretion ```

Question 33

what is the difference between immature and mature epithelial cells?

Answer 33

immature - secrete within crypt (watery usually) | mature - absorb

Question 34

why have lots of watery secretion?

Answer 34

to keep openings clean from bacteria

Question 35

what pump does secretion work though in small intestine? how does it work?

Answer 35

chloride pumps Cl is moved from one side of epithelium to the other which is turned on by cAMP Na ions are involved in another pump (water follows) to balance charge

Question 36

what are two epithelial cell types in the small intestine? what do they release?

Answer 36

paneth - cryptdins and defensins | goblet cells - mucus

Question 37

what 3 things control small intestinal secretion?

Answer 37

1) local distension (when food is present) 2) secretin/CCK (minor) 3) secretagogues

Question 38

what 3 things control small intestinal secretion?

Answer 38

1) local distension (when food is present) 2) secretin/CCK (minor) 3) secretagogues

Question 39

what is the function of the mucus in the large intestine?

Answer 39

lubrication | adhesive medium for conversion of chyme into feces

Question 40

what 4 things control large intestine secretion?

Answer 40

1) tactile stimulation 2) local distension 3) parasym NS (incr production) 4) emotions, stress (diarrhea)

Question 41

what causes cholera?

Answer 41

vibrio cholerae in contaminated food/water

Question 42

what does cholera do to the body?

Answer 42

causes severe gastroenteritis in children, leading to severe diarrhea, dehydration, and death

Question 43

what are the two subunits of cholera toxin and how do they enter the cell?

Answer 43

B and A subunits 1) B subunit binds to enterocyte membrane with high affinity 2) A subunit releases towards the membrane and enters cell membrane

Question 44

what does cholera toxin (A subunit) do once it's entered the cell?

Answer 44

1) splits into two smaller subunits (A1 and A2) 2) activates adenylate cyclase 3) converts ATP to cAMP, which is a potent Cl secretagogue

Question 45

what effects does the cholera toxin have once cAMP is produced?

Answer 45

increased Cl secretion, which affects Na and water | Hypersecretion of H2O leading to severe dehydration

Question 46

how do you treat cholera?

Answer 46

oral rehydration therapy, making intake more than output

Question 47

what is cystic fibrosis caused by? what effect does this have? why is this significant

Answer 47

caused by disfunctional CFTR, which causes little Cl and water secretion, and creates a thick mucus CF can offer some protection against cholera

Question 48

where does enzymatic digestion start and end?

Answer 48

mouth | small intestine

Question 49

what 4 structures secrete digestive enzymes?

Answer 49

salivary glands gastric pits exocrine pancreas liver

Question 50

what is the difference between simple and complex carbs?

Answer 50

complex: polysaccharides (starch, glycogen, cellulose) simple: disaccharides (sucrose, lactose, maltosE) and monosaccharides (glc, fru)

Question 51

what structures secrete amylase?

Answer 51

salivary gland gastric pits pancreas luminal?

Question 52

what are 2 brush border enzymes?

Answer 52

sucrase-isomaltase (sucrase, maltase) | lactase

Question 53

what are 2 brush border enzymes?

Answer 53

sucrase-isomaltase (sucrase, maltase) | lactase

Question 54

what receptors are located on the Apical membrane? Basolateral membrane?

Answer 54

Apical:SGLT1 (Glu and Gal), GLUT5 (Fru) Basolateral: GLUT2 (Monosaccharides)

Question 55

how does each receptor transport carbohydrates across the membrane?

Answer 55

SGLT1: secondary active transport GLUT5: facilitated diffusion GLUT2: facilitated diffusion

Question 56

what are glucose levels in the blood, cytoplasm, and lumen?

Answer 56

blood: 4-7mM cytoplasm: 10mM lumen: 1-40mM

Question 57

what processes break down protein?

Answer 57

1) mastication 2) denaturation 3) acid hydrolysis (activation of pepsinogen) 4) enzymatic breakdown (break peptide bonds) 5) proteolytic enzymes (non specific) 6) endopeptidases (pepsin, trypsin, chymotrypsin) 7) exopeptidases

Question 58

what is the end result of protein digestion?

Answer 58

AAs and short peptide chains

Question 59

what is the end result of protein digestion?

Answer 59

AAs and short peptide chains

Question 60

how are small peptides carried across the cell?

Answer 60

carried intact via transcytosis

Question 61

what happens to tri- and di-peptidases in the cell?

Answer 61

proton pumps pump peptide inside peptidases in cytoplasm break them down into AAs single AAs are transferred into cell with Na

Question 62

what 3 enzymes break down lipids?

Answer 62

``` salivary lipase gastric lipase pancreatic lipase (monoglycerides and FFAs) ```

Question 63

what 3 enzymes break down lipids?

Answer 63

``` salivary lipase gastric lipase pancreatic lipase (monoglycerides and FFAs) ```

Question 64

how much water is absorbed in the small intestine and large intestine?

Answer 64

small - 92% (osmosis) | large - 6-7%

Question 65

what is giardia lamblia?

Answer 65

common intestinal parasite transmitted via fecal-oral

Question 66

how does G. lamblia affect the body?

Answer 66

disrupts cytoskeleton and causes MLCK activation to increase paracellular permeability? leading to decreased digestion, reduced absorption and diffuse microvillus shortening