7: GI Tract Motility

Question 1

Slow waves

Answer 1

Depols and repols of membrane potential in GI smooth muscle

Question 2

How do slow waves cause contraction

Answer 2

Greater number of APs on top of slow waves creates larger contraction

Question 3

Three things that increase slow wave amplitude

Answer 3

Ach, parasymps, stretch

Question 4

Two things that decrease slow wave amplitude

Answer 4

NE, sympathetics

Question 5

ICCS: Interstitial Cells of Cajal

Answer 5

GI pacemakers that spontaneously generate and propagate slow waves; slow waves spread to smooth muscle via gap junctions

Question 6

Where are ICCs located?

Answer 6

Myenteric plexus and smooth muscle

Question 7

Phasic vs tonic contraction

Answer 7

Phasic: periodic contraction and relaxation
Tonic: maintain constant contraction

Question 8

4 places where tonic contraction occurs

Answer 8

Stomach, lower esophagus, ileocecum, internal anal sphincter

Question 9

Which cannot occur after a vagotomy, primary or secondary peristaltic waves?

Answer 9

Primary

Question 10

What controls the involuntary swallowing reflex

Answer 10

Medulla

Question 11

Involuntary swallowing reflex steps

Answer 11

1. Food in pharynx -> sensory input via CN 9 and 10
2. Swallowing center in medulla -> brainstem nuclei
3. Efferent input to pharynx

Question 12

Achalasia

Answer 12

Impaired peristalsis and incomplete LES relaxation during swallowing

Question 13

What causes achalasia?

Answer 13

Decreased ganglion cells in myenteric plexus -> LES stays mostly closed during swallowing

Question 14

Presentation of achalasia

Answer 14

Regurgitation, heartburn, dysphagia

Question 15

How to Dx achalasia

Answer 15

Barium swallow study

Question 16

What causes GERD

Answer 16

Motor abnormalities -> low pressure in LES -> persistent reflux -> inflammation

Question 17

Secondary causes of GERD

Answer 17

Increase in intra-gastric pressure; after a large meal, pregnancy, heavy lifting, etc.

Question 18

Complications associated with GERD

Answer 18

GI bleed, esophagitis, scar tissue/strictures, Barrett’s esophagus

Question 19

Max frequency of peristalsis in caudad stomach

Answer 19

3-5 waves/min

Question 20

Why is gastric emptying closely regulated

Answer 20

Provide time for digestion and neutralizing gastric H in duodenum

Question 21

SIBO

Answer 21

Colonic bacterial overabundance that can disturb SI motility -> nausea, anorexia, bloating

Question 22

Slow gastric emptying sx

Answer 22

Fullness, loss of appetite, nausea, sometimes vomiting

Question 23

What can cause slow gastric emptying

Answer 23

Gastric ulcer, cancer, eating disorders, vagotomy

Question 24

Tx for slow gastric emptying

Answer 24

Pyloroplasty, balloon dilation

Question 25

Gastroparesis

Answer 25

Slow emptying of stomach in absence of mechanical obstruction

Question 26

What can cause gastroparesis?

Answer 26

DM, injury to vagus nerve

Question 27

Sx of gastroparesis

Answer 27

N/V, early feeling of fullness, weight loss, abd bloating and discomfort

Question 28

IPAN stands for?

Answer 28

Intrinsic primary afferent neuron

Question 29

Slow waves in SI vs stomach

Answer 29

In SI, slow waves dont initiate contractions, they just set max frequency for contractions

Question 30

Vomiting reflex events

Answer 30

reverse peristalsis in SI -> stomach and pyloric relaxation -> forced inspiration to increase abdominal pressure -> movement of larynx -> LES relaxation -> glottis closes -> forceful expulsion of gastric contents

Question 31

Regulation at ileocecal junction: distention of ileum vs colon

Answer 31

Ileum distention -> relaxes ileocecal sphincter

Colon distention -> contracts sphincter to prevent backflow

Question 32

Where is the ENS in the LI?

Answer 32

Concentrated beneath tenia coli

Question 33

What type of nerve innervates external anal sphincter?

Answer 33

Somatic pudendal nerves