GI Motility, Stomach Physio

Question 1

7 sphincters

Answer 1

• UES
• LES
• pyloric
• oddi
• ileocecal
• internal anal
• external anal

Question 2

parasympathetic NS acts thru _________ to stim enteric NS activity

Answer 2

dorsal motor nucleus of vagus nerve

Question 3

ACh

Answer 3

excitatory 
smc contraction
intestinal secretions
enteric hormone release
blood vessel dilation

Question 4

NE

Answer 4

inhibitory
extrinsic sympathetic neurons
opposite effect of ACh

Question 5

myenteric plexus

Answer 5

between longitudinal and circular layers of m. in tunica musclularis

exerts control over digestive tract motility

Question 6

submucous plexus

Answer 6

buried in submucosa

principal role = senses envious w/i lumen (regulates blood flow and epithelial cell function)

Question 7

equivalent of Z-lines in smc

Answer 7

dense bodies, points of attachment for myofilaments

single-unit muscle cells contract as a single unit bc electrically linked by gap junctions

Question 8

interstitial cells of cajal

Answer 8

intestinal wall, between longitudinal and circular layers of muscular externa

transmission of info from enteric neurons to smc

PACEMAKER cells, have capacity to generate basic electrical rhythm (slow wave activity)

Question 9

esophageal achalasia

Answer 9

motor disorder characterized by complete loss of contraction and relaxation of m. used to move contents down esophagus

Question 10

paraesophageal hernia

Answer 10

stomach protrudes thru diaphragm into chest alongside esophagus

Question 11

negative regulators of esophageal smc (relax)

Answer 11

VIP (vasoactive intestinal polypeptide)

Nitric oxide

Question 12

positive regulators of esophageal smc (contraction)

Answer 12

ACh

Substance P

Question 13

ileocecal valve

Answer 13

• joining point between lg and small intestines

- controls flow and retains contents of colon (gut microbiota)

Question 14

primary movements in colon

Answer 14

haustral contractions and mass movements, mostly in ascending and transverse colon

Question 15

haustral contactions

Answer 15

colon

slow, about every 30 mins, last approx 1 in

stim by stretch

Question 16

mass movements

Answer 16

colon

slow, powerful contractions

move over colon 3-4x daily, typically after meals

stim by GASTRIN release when stomach receives food

Question 17

stomach functions

Answer 17

• reservoir
• food mixing
• kneeding of food
• metered emptying in response to duodenal feedback
• vomit

Question 18

stomach secretions

Answer 18

H+ 
Pepsinogens/pepsin
Mucus
Intrinsic factor
Water

Question 19

converts pepsinogen –> pepsin

Answer 19

H+

Question 20

kills microbes, denatures protein

secreted prod of stomach

Answer 20

H+

Question 21

enterochromaffin-like cell

Answer 21

histamine secretion

Question 22

parietal cells

Answer 22

acid, intrinsic factor secretion

Question 23

chief cells

Answer 23

pepsinogen secretion

gastric lipase secretion

Question 24

cell surface pH of gastric mucosal barrier

Answer 24

~7

Question 25

pH of gastric juice

Answer 25

1-2

Question 26

agents that disrupt gastric mucosal barrier

Answer 26

``` weak acids (aspirin) alcohols (EtOH) NSAIDs (indomethacin) detergents (bile salt/acids) inflammation (H. pylori) ```

Question 27

most common cause of gastritis and peptic ulcer disease

Answer 27

H. pylori infection

Question 28

breakage of gastric mucosal barrier allows back diffusion of

Answer 28

H+ (damages tissue)

Question 29

____ strongly increases vascular permeability

Answer 29

HISTAMINE

Question 30

gastrin hormone MOA

Answer 30

endocrine, secretion

Question 31

gastrin releasing peptide MOA

Answer 31

neurocrine, action potential

Question 32

histamine MOA

Answer 32

paracrine, diffusion

Question 33

gastric mucosa cells produce _____ hormones

Answer 33

peptide

Question 34

Gastrin

Answer 34

prod by G cells, Antrum of stomach, target parietal cell in stomach stim acid secretion stim pepsinogen secretion

Question 35

Somatostatin

Answer 35

prod by D cells inhibits gastrin release

Question 36

cell source of gastrin releasing peptide

Answer 36

vagal nerve endings *neurocrine not hormone

Question 37

CCK

Answer 37

source: duodenum and jejunum target: pancreas and gallbladder inc enzyme secretion, contraction

Question 38

secretin

Answer 38

source: duodenum target: pancreas and gallbladder inc HCO3- and fluid secretion by pancreatic and bile ducts

Question 39

gastrin releasing peptide target/action

Answer 39

target: antrum inc gastrin release

Question 40

somatostatin

Answer 40

source: stomach and duodenum target: stomach, pancreas, liver dec gastrin release, dec endocrine and exocrine secretions, dec bile flow

Question 41

gastrin inhibitory peptide

Answer 41

source: duodenum and jejunum target: pancreas action: dec fluid absorption

Question 42

site of B12 absorption

Answer 42

distal ileum

Question 43

cephalic phase

Answer 43

everything short of having food enter stomach

Question 44

2 paths by which vagus nerve exerts its effects

Answer 44

direct stim by ACh indirect through gastrin

Question 45

gastric phase

Answer 45

1. dissension of stomach --> activates stretch receptors and inc in pH --> chemoreceptors in mucosa =mucin, lots of acid, pepsinogen are secreted. 2. enteric NS + gastrin release --> smc contraction

Question 46

bulk of protein digestion occurs in the

Answer 46

SI

Question 47

resting pH of sotmach

Answer 47

1-2

Question 48

stimulated pH of stomach

Answer 48

>/=3

Question 49

H2 receptor blockers and PPIs reduce ___ secretion but have no effect on ___ production/action

Answer 49

H2 receptor blockers and PPIs reduce [H+] secretion but have no effect on [GASTRIN] production/action

Question 50

majority of chyme entering SI is ____mm

Answer 50

<1mm

Question 51

CCK and GIP are activated by the presence of

Answer 51

lipids and carbs

Question 52

secretin is activated by

Answer 52

dec pH

Question 53

intestinal phase

Answer 53

digestive prod and H+ move into SI --> release of CCK, GIP, secretin (inhibit H+, pepsinogen, and stomach mixing, slow passage of chyme to SI which may be filled/overactive)

Question 54

duodenal stretch and chemoreceptors action on myenteric plexus

Answer 54

inhibition