Motility Physiology

Question 1

2 main plexus networks of enteric nervous system (ENS)

Answer 1

myenteric- b/w outer and middle muscle layers

submucosal- b/w middle layer and mucosa

Question 2

myenteric fn

Answer 2

motor fn of longitudinal and circular muscle, stim thru ACh and inhib via NO

Question 3

submucosal plexus fn

Answer 3

controls intestinal secretion

Question 4

para control over GI tract

Answer 4

mostly vagus, typically result in muscle contraction in small and large intestine

Question 5

symp fn on GI tract

Answer 5

shunts blood away from splanchnic circulation, suppresses digestive fn

via NE

Question 6

describe the flow of peristalsis

Answer 6

response to wall stretch is contraction of circular muscle w/ relaxation of long muscle in propulsive segment, opposite contratctions in receiving segment

wave moves oral to caudal

Question 7

define trituration

Answer 7

crushing food by stomach to increase surface area

Question 8

intestinal mixing movements

Answer 8

segmentation by intestines, mixes enzymes w/ nutrients

Question 9

reservoir fns

Answer 9

performed by stomach and colon- gastric body stores ingested food, colon holds material for absorption of water until time for defecation

Question 10

7 GI sphincters

Answer 10

UES

LES

pylorus

sphincter of Odi (pancreatic
and bil ducts insert into duodenum)

ileocecal valve

internal and external sphincters of the anus

Question 11

muscle division of esophagus

Answer 11

upper third is striated muscle, rest is smooth muscle

Question 12

primary vs secondary peristalsis

Answer 12

primary is voluntary act of swallowing, secondary is when primary fails to clear bolus (reflexively)

coordinated w/ LES relaxation on initiation of swallow via vagus

Question 13

gastric accomadation occurs via:

Answer 13

relaxation of the fundus, increasaing gastric volume

Question 14

3 types of gastric relaxation

Answer 14

receptive- from act of swallowing

adaptive- vago vagal reflex from gastric distension

feedback- nutrients in SI signal stomach

Question 15

3 antral pump phases

Answer 15

propulsion- gastric action potentials create leading and trailing contractions, pushing food toward antrum

emptying- small amount is emptied, pylorus closes

retropulsion- trailing contraction forces food against closed pylorus

goes at 3 cycles a min until full emptying

Question 16

hyperosmolality of duodenal contents causes:

Answer 16

decrease in gastric emptying

Question 17

MMC occurs when? what 3 phases?

Answer 17

interdigestive state only in SI, when digestion complete

1. silent, no contraction
2. irregular contractions
3. regular contractions

repeat in cycle, independent of extrinsic nervous control

Question 18

3 fns of MMC

Answer 18

1. prevents accumulation of bile in gallbladder
2. clear indigestible debris (clears larger particles from antrum)
3. prevent microbial overgrowth in SI

Question 19

describe power propulsion and its fn

Answer 19

strong, longer circular muscle contraction

longer distances on SI and LI

retrograde during emesis, antegrade from noxious stimuli (diarrhea)

also normal for clearing material from colon

Question 20

trigger for colon mass movements

Answer 20

increased delivery of ileal chyme into ascedning after meal- gastrocolic reflex after meal

Question 21

primary site for water reabsorption in colon

Answer 21

transverse colon

descedning and ascending more for conduits, power propulsion

Question 22

3 motor patterns of SI

Answer 22

MMC, segmentation, power propulsion

Question 23

2 motor patterns of LI

Answer 23

haustration, power propulsion