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Flashcards in GI Motility Deck (53):
1

Which of the regional motility patterns involves intestinal smooth and regular skeletal muscle?

Swallowing and defacation

2

opiods have (constipating/laxative) effect. How so?

Constipating, promote absorption of fluid and electrolytes

3

Parasympathetic regulation of the myenteric plexus involve (pre/post) ganglionic neurons while sympathetic involve (pre/post) gaglionic neurons.

Parasympathetic = pre ganglionic

sympathetic = post ganglionic

4

3 important inhibitory motor neurons of the ENS

VIP, ATP, and NO

5

List 6 important interneurons of the ENS

5HT
GABA
Ach
Dopamine
Enkephalin
Somatostatin

6

Serotonin
-Net effect on motility:
-Net effect on mucosal secretion/absorption:

-pro-kinetic
-stimulates fluid and electrolyte secretion

7

Dopamine
-Net effect on motility:
-Net effect on mucosal secretion/absorption:

-anti-kinetic
-complicated

8

Enkephalin (opiate)
-Net effect on motility:
-Net effect on mucosal secretion/absorption:

-promotes symmetric segmentation
-stimulates fluid and electrolyte absorption

9

Acetylcholine
-Net effect on motility:
-Net effect on mucosal secretion/absorption:

-pro-kinetic
-stimulates fluid and electrolyte secretion

10

Vasoactive Intestinal Peptide (VIP)
-Net effect on motility:
-Net effect on mucosal secretion/absorption:

-as neurotransmitter: relaxes ISM
-In excess: secretory diarrhea
-stimulates fluid and electrolyte secretion

11

Which region(s) of the GI tract contains only skeletal striated muscle?

Mouth, pharynx, and upper esophageal sphincter (UES)

12

Which region(s) of the GI tract contains a mixed striated/smooth muscle?

Esophagus (1/3 striated, 1/3 striated/smooth, 1/3 smooth muscle) and anal sphincter

13

Which 6 regions only contain smooth muscle?

-stomach
-duodenum
-jejunum
-ileum
-colon
-rectum

14

The motility patterns of these two regions involve mostly segmentation, periodic local peristalsis, and mass movement

Colon and rectum

15

Once we start chewing and the food reaches a certain part of the pharynx, a ____ occurs which includes a swallow, then an _____ of contraction that goes down entire esophagus

-peristaltic wave
-orderly wave

16

What must happen way ahead of the arrival of the orderly wave? Why?

The lower esophageal sphincter relaxes (LES)
-ensures that bolus of food enters the stomach

17

In contrast to vascular smooth muscle, intestinal smooth muscle cannot respond to synaptic input unless it is also innervated by what?

Intestinal Cells of Cajal (ICC) (they are the pacemakers!)

18

What are the Intestinal Cells of Cajal? What is an important feature they contain?

-Cells that form a network over the ISM and are auto-excitatory
-pacemaker activity to generate rhythmic depolarization-repolarization pattern in ISM = slow wave rhythm = bioelectric rhythm

19

ISM only responds to synaptic input from enteric neurons when the ISM membrane potential is in the ____ phase of the slow wave pattern

Plateau phase

20

When the ISM is innervated only by the intestinal Cells of Cajal, what happens? What doesn't happen?

It develops muscle tone but no motility patterns.

21

Motility patterns are programmed in the ___

enteric ganglia

22

Swallowing is a reflex initiated by food bolus by activating ___ in the _____

stretch receptors (GVA), pharynx

23

The GVA stretch receptors activated by bolus of food synapse in the ____, which then sends upper motor neuron output to the which two nuclei?

-Nucleus tractus solitarius
-nucleus ambiguus and vagal nucleus

24

What are the two things that happen to the proximal portion of stomach when food arrives?

-relaxes (receptive relaxation)
-minimal mixing of contents

25

When the distal portion of the stomach senses food, what does it initiates?

Propulsive waves (via local enteric reflexes) starting in upper 1/3 of stomach and ending at pylorus.

26

What happens to the pylorus just before the food is propelled toward the pyloric region? Why is this necessary?

The pylorus closes. --insures that oly chyme particles will leave the stomach during this gastric phase of digestion

27

What is the predominant motility pattern in the small intestine during the intestinal phase of digestion?

What is it during the inter-digestive period?

digestion: asymmetrical segmentation

interdigestive period: periodic MMCs

28

What are MMCs

Migrating motor complexes:
- waves of activity through the intestines in a regular cycle during a fasting state.
-trigger peristaltic waves, which facilitate transportation of indigestible substances through the small intestine, past the ileocecal sphincter, and into the colon

29

Serves a cleansing role--makes sure crap that got left behind during digestive period is expelled from stomach--discourages bacterial growth

MMC

30

The MMC is initiated what region?

Go through cascade that prompts the MMC

Pacemaker region--distal stomach

Prompted by vagus --> release motilin --> acts on enteric neurons in pacemaker region to start propulsive pattern

31

Dysfunction of what disrupts the MMC?

autonomic dysfunction

32

Predominant motility pattern of colon

symmetrical segmentation--simple mixing without net movement

33

3 types of control of defecation

-local reflex
-autonomic
-voluntary

34

Major changes in esophageal function with scleroderma

attacks smooth muscle so esophagus and sphincter is impacted

-slight delay in UES
-decreased middle esophagus and lower
-decreased LES

35

Major changes in esophageal function with Achalasia (failure of smooth muscle fibers to relax)

Pressure is too high so food is not passing through and getting stuck

-slight delay in UES
-slight decrease in upper esophagus
-decrease in middle and lower esophagus (not as dramatic as scleroderma)
-decrease LES

36

Major changes in esophageal function with Diffuse esophageal spasm

-wave like pattern of middle and lower esophagus
-increased duration of LES

37

Major changes in esophageal function with pharyngeal paralysis (like in muscular dystrophy or Parkinson's--skeletal muscle is impacted, smooth muscle is ok)

-all affected except middle and lower esophagus
-LES is normal but has slight sigmoid curve)

38

What does effect does vagotomy (resection of vagal nerve) have on intraluminal pressure during gastric accommodation of food?

-stomach wont have as large of a compliance and pressure goes up tremendously with increase in volume

*need an intact vagus in order to have receptive relaxation of stomach!
*also need intact ENS but can't do job alone

39

In looking at a graph comparing the change in diameter of the proximal and distal stomach during gastric phase of digestion, the proximal stomach stays relatively constant meanwhile the distal goes up and down in wave like matter. Why?

Proximal stomach does not have a lot of contraction meanwhile the distal undergoes contractile movements

40

CCK effect on gastric emptying--what do you see on graph

slows down rate so will see food remain in stomach longer as time progresses

41

What is the effect o fnausea on gastric emptying?

delays emptying

-and vice versa: delayed emptying can cause nausea

42

One complication of long-standing diabetes is loss of ANS function. How does this affect gastric transit and acid secretion during the gastric phase?

transit time: slower (longer)
HCl secretion: no change

43

Gastrocolic reflex is an example of autonomic regulation of ENS. Helpful in regulating digestion and absorption but not necessary. describe it

gastric distension --> GVA via vagus to NTS ---(interneurons)--> preganglionic parasympathetic neurons in sacral spinal cord ---pelvic splanchnic nerves---> myenteric neurons in distal colon --> increased motility and mass movement in distal colon

44

is motor activity in the colon all coordinated?

-Sometimes, activities are coordinated
-mass movement of transverse and descending occur at different times
-Anal sphincter and rectum seems to have life of its own

45

Internal anal sphincter is what time of muscle and innervated by what nerve?

-thickening of intestinal smooth muscle
-pelvic splanchnic nerve

46

External anal sphincter is what type of muscle and innervated by what nerve?

Skeletal muscle, peripheral nerves (pudental nerve)

47

The internal anal sphincter works similar to what esophageal sphincter?

LES
-when food reaches canal, relaxes

48

How does external anal sphincter work

Almost immediately , EAS quickly takes over and keeps anus closed. Good sot hat we dont have to take a shit every time the rectum undergoes a propulsive movement

*NEED INTACT INNERVATION THOUGH!

49

Internal anal sphincter is (voluntary/involuntary) while the external is (voluntary/involuntary)

internal-involuntary
external-voluntary

50

In the large intestine, symmetrical segmentation dominates but is interrupted at infrequent intervals by a _____

regional propulsive mass movement

51

Requirements for defacation and swallowing (3)

1. coordinated activity of striated muscle innervated by spinal nerves
2. coordinates activity of smooth muscle innervated by ENS
3. sensory nerves and ANS are required

52

Fecal continence requires the following: (5)

intact:
1. internal and external anal sphincters
2. pudental nerves --are sensory and also regulate external sphincter
3. sacral autonomic nerves
4. sacral spinal cord
5. forebrain and corticospinal pathways

53

Regulation of defacation reflex

intrarectal pressure increases ---> relax internal sphincter --> GVA to sacral cord and cortex --> constrict external sphincter --> decide what's next --> if ok to defecate, use program in sacral cord (modulated by cortical centers)