Gi Physiology: The Basics

Front 1

What is the enteric nervous system?

Back 1

Intrinsic nervous system (Meissner's and Aurbach's plexuses)
Contained within the gut (complete)
Esophagus to anus
Required for normal function

Front 2

What does the submucosal plexus (Meissner's) do?

Back 2

Found in submucosa
Controls secretions, circulation, and muscularis mucosae contractions

Front 3

What does the myenteric plexus (Aurbach's) do?

Back 3

Between layers of muscularis externis
Controls motility

Front 4

What is ACh's purpose in the enteric nervous system?

Back 4

Increase activity
*Can also be used by the extrinsic

Front 5

What is VIP and what does it do?

Back 5

Vasoactive intestinal polypeptide
Increase secretion
Decrease motility

Front 6

What does norepinephrine do in the enteric nervous system?

Back 6

Decreases activity, especially motility

Front 7

What is the major inhibitory neurotransmitter of the enteric nervous system?

Back 7

Nitric oxide
It is REQUIRED to cause relaxation

Front 8

What is Hirschsprung's disease?

Back 8

Loss of the NO-ergic neurons in a part of the colon causing it to become tightly contracted
Causes obstruction

Front 9

What is achalasia?

Back 9

Lower esophageal sphincter doesn't relax
Swallowing becomes painful

Front 10

What are endorphins?

Back 10

Opiods via the mu receptors
Decrease peristalsis
Increase mixing motions
Net: slow down and absorb more
*Can cause constipation

Front 11

How do the parasympathetic and sympathetic nervous systems affect GI activity?

Back 11

Parasympathetic: Increase activity of intrinsic neurons and excites most GI function
Sympathetic: Decrease activity of intrinsic neurons and depresses most GI function

Front 12

What is the "local" reflex of the stomach?

Back 12

Distension in stomach increases gastric motility
Neurons located entirely within enteric nervous system

Front 13

What are the "long loop" reflexes and what is their purpose?

Back 13

Gastrocolic reflex:
Distension in stomach
Relaxation in the colon
Purpose: "Get ready, here comes some food"
Afferent to sympathetic ganglia then back to gut

Front 14

How are GI reflexes named?

Back 14

FIrst part of name s origin of reflex
Second part of name is where effect occurs

Front 15

What are the "longest" reflexes?

Back 15

Cell body in dorsal root ganglion (not enteric)
To CNS
Back to gut
Ex: response to pain inhibition

Front 16

What is the source and stimulus of gastrin?

Back 16

Peptide hormone secreted by G cells in the pyloric glands of the stomach
Elicited by distention of the stomach

Front 17

What does gastrin do?

Back 17

Increase acid secretion
Increase motility
Increase pancreatic enzyme secretion

Front 18

T or F: All of the GI hormones travel through the blood.

Back 18

True

Front 19

What is the source and stimulus of secretin?

Back 19

Peptide hormone secreted by the S cells of the intestine Presence of acid in duodenum

Front 20

What does secretin do in the stomach? Pancreas? Liver?

Back 20

Stomach:
Decrease gastrin, acid, and motility
Increase enzyme (pepsin)
Pancreas:
Increase bicarbonate and pancreatic enzyme
Liver:
Increase bicarbonate

Front 21

What is the source and stimulus of CCK-PZ (cholecystokinin pancreozymin)?

Back 21

Peptide hormone from the I cells of the intestine (duodenal mucosa)
Stimulated by fats in the duodenum

Front 22

What does CCK-PZ do?

Back 22

Gall bladder contraction
Increase enzyme secretion in pancreas
*Also acts in brain and liver - satiety

Front 23

What is the source and stimulus of GLP-1 (glucagon-like peptide 1)?

Back 23

Peptide hormone secreted by L cells of ilium/colon
Stimulated by nutrients, particularly fats and dietary fiber in intestine

Front 24

What does GLP-1 do?

Back 24

Increased synthesis of insulin
Decrease gastric acid and mobility

Front 25

What is the source and stimulus of GLP-2?

Back 25

Peptide hormone from L cells of the intestine
Stimulated by nutrients, particularly fats and dietary fiber as well as intestinal injury

Front 26

What does GLP-2 do?

Back 26

Trophic growth factor for intestine causing growth of villi and mucosal hyperplasia

Front 27

What is the source and stimulus of amylin?

Back 27

Peptide hormone from Beta cells of the pancreatic islets
Stimulated by increase in blood glucose
*Co-released with insulin

Front 28

What does amylin do?

Back 28

Trophic to pancreas
Decrease motility and control of appetite
Blood glucose control

Front 29

What is the source and stimulus for motilin?

Back 29

Peptide hormone from ECFL and Mo cells of stomach, small intestine, and colon
Stimulus is unknown

Front 30

What does motilin do?

Back 30

Increase motility
Major regulator of the migrating motor complex

Front 31

What is splanchnic circulation?

Back 31

Blood supply going to the GI tract plus the pancreas, spleen, and liver

Front 32

What is the hepatic portal system?

Back 32

Veins leaving the intestine break into capillaries again in liver
Gives liver first choice of nutrients and toxins absorbed

Front 33

What is counter-current blood flow?

Back 33

In the villi
Arteriole entering flows alongside venule leaving
Exchange of oxygen and CO2

Front 34

T or F: The tip of the villi is oxygen rich.

Back 34

False

The tip is hypoxic due to the counter current blood flow

Front 35

Where do the replacement cells for the tip of the villi come from and why is the sloughing of the tip good?

Back 35

Replacement cells come from the base of the villi
The rapid turn over is protective of the system from bacteria

Front 36

What is the function of P-glycoprotein (MDR-1 gene product)?

Back 36

To remove drugs/other exogenous substances from cell to the lumen (prevent absorption)