Gastric Motility

Question 1

How do the sections of the stomach differ in terms of function?

Answer 1

the body and fundus are more for the reservoir function while the antrum is more for the emulsification and grinding of food

Question 2

How does the stomach change to accommodate the food being pushed into it?

Answer 2

It doesn’t just expand like a balloon, it undergoes receptive relaxation as a part of the swallowing reflex and in response to gastric mechanoreceptors

Question 3

How much can the stomach store?

Answer 3

2-4 L

Question 4

What neurotransmitters are released during receptive relaxation? Why is this unusual?

Answer 4

ACh is releases from the vago-vagal reflex arch onto interneurons that secrete VIP and NO to do the actual relaxation

unusually because ACh usually triggers ocnstriction in the GI system

Question 5

Expansion of the stomach also signals forward to what two reflexes?

Answer 5

gastrocolic reflex

gastroileal reflex

Question 6

What is the gastrocolic reflex?

Answer 6

induces the need to defacate after ingesting a meal

Question 7

What is the gastroileal reflex?

Answer 7

causes the ileoceccal valve to relax and transfer contents from the small intestine into the large intestine

essentially making room for what’s coming down the gaunlet

Question 8

Describe the four things that take place in terms of digestion in the stomach?

Answer 8

1. low pH facilitates protein denaturation
2. Pepsin endopeptidase releases peptides
3. gastric lipase prduces free fatty acids
4. mechanical movement important for emulsificaiton of fats

Question 9

What can be absorbed in the stomach?

Answer 9

gastric absorption is minimal because there’s no active transport in the stomach, but some lipid-soluble substances like alcohol and aspirin can be absorbed by diffusion

Question 10

Emptying of liquids from the stomach invovles what kind of contraction where?

Answer 10

tonic contraction of the proximal stomach (the reservoir) - these are the longer contractions

Question 11

Emptying of solids involves what kind of contraction and where?

Answer 11

more phasic contractions of the antral pump (the pylorus)

Question 12

How small must food be to pass through the pylorus?

Answer 12

less than 2 mm

Question 13

About how many cycles per minute occur with the phasic contractions?

Answer 13

about 3 cycles per minute

Question 14

What’s the first contraction that occurs in the cycle?

Answer 14

a circulferential contraction sweeps toward the pylorus resulting in anterograde and retrograde propulsion of material

Question 15

WHat happens when a second contraction comes in the cycle?

Answer 15

it mixes contents further

sufficient to cause transient and partial opening of the pylorus to allow small particles to exit the stomach, but larger particles are propelled back into the stomach to be further dispersed by subsequent contractions

Question 16

What’s the term for the 3-5 cycles/per minute thing?

Answer 16

basic electrical rhythm (BER)

Question 17

What is determined by the BER? What can be altered by neural and hormonal input?

Answer 17

frequency is determined by the BER but amplitude can be altered by neural and hormonal input (ACh and gastrin)

Question 18

What determines the magnitude of contraction then?

Answer 18

the number of action potentials that summate on the crests of the slow waves

Question 19

What happens to the contraction as it approaches the closed pyloric sphincter?

Answer 19

it strengthens and speeds up

Question 20

What are 5 factors that will promote rapid emptying of the stomach?

Answer 20

1. tonic contraction of the reservoir
2. deep peristaltic waves along the body with deep constrictions of the antral waves
3. a wide opening of the pylorus
4. duodenum relaxation
5. peristaltic duodenal contractions

Question 21

What are the factors that will delay gastric emptying?

Answer 21

1. prolonged relaxation of the reservoir
2. shallow peristaltic waves along the gastric body
3. small pyloric opening
4. duodenal constriction
5. segmenting duodenal contractions (not peristalsis)

Question 22

What do feedback mechanisms from the duodenum do to gastric emptying?

Answer 22

neural, hormoneal and mechanical signals feed back to slow gastric emptying by diminishing the intensity of the contractile wave

“I’m busy, don’t send anythnig else”

Question 23

Describe how emptying rate depends on the meal?

Answer 23

high glucose meals are processes the fasted, so emptying rate is the fastest

fats take longer, so emptying is delayed

Question 24

What are the three things in the duodenum that will inhibit gastric emptying?

Answer 24

1. acid in the duodenum
2. fat in the fuodenum
3. increasing osmolality of the duodenal contents

Question 25

Acid in the duodenum inhibits gastric emptying via what mechanism?

Answer 25

neural (enteric and vagal) and hormonal (secretin and somatostatin)

Question 26

Fat in the duodenum inhibits gastric emptying via what mechanism?

Answer 26

hormonal (CCK) mehcnisms and enteric neural mechanisms

Question 27

How does konjac flour work?

Answer 27

It’s a dietary fiber that creates a thick gel in the stomach so that gastric empting is delayed and you feel full longer

issue is choking hazard

Question 28

How does palm oil work in theory?

Answer 28

It’s a fat that is thought to activate CCK to slow emptying and promote satiety

Question 29

What is phase I of the migrating motor complex?

Answer 29

quiescent phase - lasts 20-60 minutes

Question 30

What is phase II of the migrating motor complex?

Answer 30

irregular peristaltic contractions lasting 10-30 minutes

promotes increase in gastric and pancreatic juices

Question 31

Describe phase III of the mograting motor complex.

Answer 31

intense contractions lasting 5-10 minutes

the pylorus opens fully

Question 32

What is pyloric stenosis? Trx?

Answer 32

congenital condition where pylorus fails to relax after a meal leading to malnutrition and dehydration. Treated with surgical myotomy.

Question 33

What is gastroparesis? WHat patient population has an issue with this?

Answer 33

reduced gastric emptying often due to diabetic neuropathy involving the vagus and enteric nerves in the stomach such that the stomach fails to generate enough force to empty the stomach.

Question 34

What are some other causes of gastroparesis besides diabetic neuropathy?

Answer 34

Other causes include surgery, drugs, cancer treatments.

Question 35

What is the opposite of gatsroparesis?

Answer 35

dumping syndrome

Question 36

Describe dumping syndrome.

Answer 36

rapid gastric emptying….

rapid entry of gastric contents intot he duodenum represents an osmotic challenge, so water moves intot he lumen resulting in hypovolemia and reduced BP. you get nause,a weakness, dizziness, sweating, diarrhea, heart palpitations, etc.

Question 37

What are some causes of dumping syndrome?

Answer 37

gastric gypass
surgery
vagotomy
high sugar-containing meals

Question 38

What brain structure coordinates vomiting?

Answer 38

the vomiting center in the medulla

Question 39

What’s the first step in the vomiting sequence?

Answer 39

increased salivation thorugh parasympathetic activation to protect enamel from erosion

Question 40

What is the second step in the vomiting sequence?

Answer 40

retro-peristalsis of small intestinal contents up into the stomach thorugh a relaxed pyloric sphincter

Question 41

What’s usually the third step in the vomiting sequence?

Answer 41

retaching helps get the new stomach contents up into the esophagus

Question 42

What things happen when you actually vomit?

Answer 42

1. glottis closes to prevent aspiration
2. hyoid moves upward and forward to open the UES
3. contraction of the diaphragm and abdominal muscles propels stomach contents into the esophagus and then out the oral cavity

Question 43

What are some important inhibitors of vomiting?

Answer 43

dopamine
histamine
serotonin