Lec 11 GI Motility

Question 1

What plexus is between submucosa and circular muscle layer?

Answer 1

meisseners = mucosal plexu

Question 2

What plexus is circular and longitudinal muscle layers?

Answer 2

auerbachs = myenteric plexus

Question 3

What makes up the muscularis propria?

Answer 3

• inner circular

- outer longitudinal

Question 4

How is the longitudinal muscle layer arranged in the colon?

Answer 4

arrounded in 3 parallel bundles = tenia coli

Question 5

What cells are located in auerbach’s plexus?

Answer 5

interstitial cells of cajal = pacemaker of the gut

Question 6

What is the slow wave of GI tract?

Answer 6

• constant background rhythm
• initiated by interstitial cells of Cajal in myenteric plexus
• controls the timing of phasic contractions

Question 7

What is frequency of slow waves in stomach?

Answer 7

3 per minute

Question 8

What is frequency of slow waves in duodenum and jejunum?

Answer 8

11-12 per minute

Question 9

What is frequency of slow waves in distal small bowel?

Answer 9

7-8 per minute

Question 10

What is frequency of slow waves in colon?

Answer 10

3-6 per minute

Question 11

What is the spike activity of the stomach?

Answer 11

• contractions of smooth muscle that occur only when slow wave depolarizations reach threshold for AP
• rapid depolarization results in contraction of smooth muscle through release of Ca

Question 12

What is action of ACh on MMC?

Answer 12

increases = pro motility

Question 13

What is action of gastrin on MMC?

Answer 13

increases = pro motility

Question 14

What is action of motilin on MMC?

Answer 14

increases = pro motility

Question 15

What is action of VIP on MMC?

Answer 15

inhibits = anti-motiliy

Question 16

What is action of secretin on MMC?

Answer 16

inhibits = anti-motility

Question 17

What is action of neuropeptide Y on MMC?

Answer 17

inhibits = anti-motility

Question 18

What are the 2 major types of contractions in the small intestine?

Answer 18

peristalsis = slow proximal to distal movement; from longitudinal smooth muscle

segmentation = major contractile grinding/churning/crushing from circular smooth muscle

Question 19

What things control peristalsis?

Answer 19

• mediated by ACh
• 5HT plays a big role
• substance P may also add to contraction
• NO mediates distal relaxation

Question 20

What is function of fundus/body of stomach?

Answer 20

receptive relaxation + reservoir; regulates emptying of liquids

Question 21

What is function of antrum of stomach?

Answer 21

mixes/grinds; regulates emptying of solids

Question 22

What is fed motor pattern of small intestine?

Answer 22

slow waves w/ increased number of spike potential to promote mixing/absorption of food; segmental

Question 23

What is fasting motor pattern of small intestine?

Answer 23

• cyclic migrating motor complex

- keeps intestine swept clean of bacteria/residue

Question 24

What are the 3 phases of the migrating motor complex (MMC)?

Answer 24

Phase I: 45-60 min, no spike potentials, no contractions

Phase II: lasts 30 min; intermittent spikes + contractions [50% of slow waves associated w/ spikes]

Phase III: 5-15 min; each slow wave has spikes and contractions

Question 25

What are some common causes of small bowel dysmotility?

Answer 25

``` neuro: parkinsons, post viral scleroderma DM, hypothyroid opiates visceral neuropathy ```

Question 26

What is chronic intestinal pseudo-obstruction?

Answer 26

problem where almost no motility of certain segments of bowel; no physical obstruction but basically is obstructed

Question 27

What are characteristics of high amplitude propagating contractions [HAPC] of colon?

Answer 27

- have amplitude > 100 mmHg - occur infrequently ~6/day - function = mass movement - associated w/ defection

Question 28

What are characteristics of low amplitude propagating contractions [LAPC] of colon?

Answer 28

- have amplitude < 50 mmHg - occur > 100/day - function = transport fluid contents - associated w/ distension and flatus

Question 29

What is ogilvie's syndrome?

Answer 29

non-obstructive colonic dilation | have colonic ieus --> usually due to drugs [narcotics], post op state, electrolyte imbalance, immobility

Question 30

How do you treat ogilvies?

Answer 30

decompress colon if needed; neostigmine to stimulate parasympathetics

Question 31

What are criteria for IBS?

Answer 31

recurrent abdominal pain or discomfort with 2 or more of - improvement with defecation - change in stool frequency - change in stool appearance/form

Question 32

What is treatment for IBS?

Answer 32

- laxative - anti-diarrheals - anti-depressants - serotonin receptor agonists

Question 33

What is mech behind IBS?

Answer 33

not clear; thought that mech is due to decrease 5HT which is responsible for controlling motility of bowel through enteric nervous system

Question 34

What things normally determine continence?

Answer 34

- stool volume and consistency - anal sphincter function - neurologic integrity - rectal sensation - rectal storage capacity - psychological motivation

Question 35

most of resting tone of anus depends on what?

Answer 35

internal anal sphincter determines most of resting tone

Question 36

What are some causes of fecal incontinence?

Answer 36

- back trauma - sphincter disruption - medical illness