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GIGU > Motility of the GI Tract > Flashcards

Motility of the GI Tract Flashcards

1
Q

What is motility in terms of the GI tract?

A

contraction and relaxation of the wall and sphincters of the GI tract, rate regulated

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2
Q

What is the role of the muscularis propria? What muscles play a role?

A

Smooth muscles that mix and circulate content of the lumen and propel through the GI tract

Circular muscle changes diameter and longitudinal muscle changes length

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3
Q

Are slow waves APs?

A

No they are depolarization and depolarization of the membrane

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4
Q

How does the number of APs on a slow wave effect contractions?

A

The greater number of APs causes a larger contraction

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5
Q

What stimulates slow waves?

A

Stretch
Ach
Parasympathetics

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6
Q

What decreases slow waves?

A

NE and sympathetics

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7
Q

What are phase contractions? Where do they occur?

A

periodic contractions followed by relaxation

esophagus, stomach (antrum), SI, and all tissue involved in mixing and propulsion

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8
Q

What are tonic contractions? Where do they occur?

A

maintain a constant level of contraction without regular periods of relaxation

orad of stomach, lower esophageal, ileocecal, and internal anal sphincters

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9
Q

Where is the submucosal plexus of the enteric nervous system found? What does it control?

A

plexus in submucosa

GI secretions and local blood flow

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10
Q

Where is the myenteric plexus found? What does it control?

A

between longitudinal and circular layers

GI movements

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11
Q

What cells are the pacemaker of GI smooth muscle?

A

Interstitial cells of Cajal (ICCs)

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12
Q

What allows ICCs to spread and propagate slow waves?

A

gap junctions

electrical activity= freq of contractions

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13
Q

Which phases of swallowing are voluntary and which are involuntary?

A

Voluntary= oral phase

Involuntary= pharyngeal and esophageal

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14
Q

What happens during the pharyngeal phase of swallowing?

A

soft palate pulled up –> epiglottis moves –> UES relaxes –> peristaltic wave of contractions initiated in pharynx –> food propelled through open UES

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15
Q

What controls the esophageal phase of swallowing?

A

Swallowing reflex and enteric nervous system

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16
Q

What are primary peristaltic waves of the esophageal phase? Can they occur after vagotomy?

A

continuation of pharyngeal peristalsis, controlled by medulla

NO

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17
Q

When do secondary peristaltic waves occur? Can they occur after vagotomy?

A

if primary wave fails to empty esophagus or if gastric contents reflux into esophagus

Can occur in absence of oral and pharyngeal phases and after vagotomy

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18
Q

What are the steps of the swallowing reflex?

A

food in pharynx –> afferent sensory input via vagus/glossopharyngeal –> swallowing center in medulla –> brainstem nuclei –> efferent input to pharynx

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19
Q

What three parts have high pressure contractions before swallowing?

A

UES
LES
esophagus

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20
Q

Why is intrathoracic pressure an issue? How does out body help with this?

A

need to keep air and gastric contents out

UES and LES closed except when food bolus is passing from pharynx to esophagus or esophagus to stomach

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21
Q

What is achlasia?

A

impaired peristalsis and incomplete LES relaxation during swallowing –> elevation of LES resting pressure

Results in backflow of food in the throat (regurgitation), difficulty in swallowing (dysphagia), heart burn, chest pain

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22
Q

What are causes of achlasia?

A

Decreased number of ganglion cells in myenteric plexuses

Degeneration preferentially involves inhibitory neurons producing NO/VIP

Damage to nerves in the esophagus preventing it from squeezing food into stomach

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23
Q

What is GERD?

A

changes in barrier between esophagus and stomach (LES relaxes abnormally or weakens) causing low pressure in LES

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24
Q

What is the job of the orad region of the stomach?

A

Receptive relaxation= decrease pressure and increase volume, caused by vagovagal reflex
Minimal contractions aka little food mixing

25
Q

What effect does CCK have on the orad region?

A

decrease contractions and increase gastric distensibility

26
Q

What is the primary event of the caudad region of the stomach? Where is it the strongest?

A

Peristaltic contraction (mid stomach to pylorus)

Increase in force and velocity as approach pylorus

27
Q

What is retropulsion?

A

Propulsion of gastric contents back into the stomach for further mixing and reduction of particle size

28
Q

What increases forces of contractions and APs?

A

parasympathetics
gastrin
motilin

29
Q

What decreases APs and force of contractions?

A

sympathetics
secretin
GIP

30
Q

What increases gastric emptying?

A

decrease in distensibility of the orad
increase peristaltic contractions of caudad
decrease tone of pylorus
increased diameter
inhibition of segmenting contractions of proximal duo

31
Q

What decrease gastric emptying?

A

relaxation of orad (increase in distensibility)
decrease force of peristaltic contractions
increase tone in pyloric sphincter
segmentation contraction in intestine

32
Q

What is the entero-gastric reflex? What stimulates it?

A

Neg feedback from duo slows down rate of gastric emptying, hormone dependent

Acid in duodenum= secretin –> gastrin inhibition
Fats in duodenum= stimulate CCK and GIP
Hypertonicity in duodenum= inhibit emptying

33
Q

What can cause slow gastric emptying? How can it be treated?

A

gastric ulcer, cancer, eating disorder, vagotomy

pyloroplasty, balloon dilation

34
Q

What is gastroparesis? What are the symptoms?

A

Slow emptying of stomach/paralysis of stomach in absence of mechanical obstruction, DM common cause, injury to vagus

Nausea, vomiting, early feeling of fullness when eating, weight loss, abdominal bloating, abdominal discomfort

35
Q

What happens when we fast? Why is this important?

A

Myoelectric complex/migrating motor complex
Periodic burst of peristaltic contractions mediated by motilin

Cleansing mechanisms to prevent small intestinal bacterial overgrowth which can lead to small bowel motility nausea anorexia and bloating

36
Q

What are segment contractions of the SI?

A

generate back and forth movements, produce no forward, propulsive movements

37
Q

What are peristaltic contractions of the SI?

A

circular and longitudinal muscles work in opposition to complement each other, reciprocally innervated

38
Q

Do slow waves initiate contractions in the SI?

A

NO
APs/spike potentials necessary for muscle contraction to occur
slow wave frequency sets max frequency of contractions
(duo (12)&raquo_space; jeju (10)&raquo_space; ileum (8) )

39
Q

What happens when the SI becomes distended?

A

Signals for the release of serotonin by enterochromaffin cells which bind to receptors in IPANs initiating peristaltic reflex

40
Q

What stimulates contraction in the SI?

A

serotonin, prostaglandins, gastrin, CCK, motilin, and insulin

41
Q

What inhibits contraction in the SI?

A

epi, secretin, and glucagon

42
Q

What is the role of the myenteric and meissner/submucosal plexus in the SI?

A

myenteric= regulate relegation and contraction of intestinal wall

meissner= sense lumen enviorment

43
Q

What are the steps of the vomiting reflex?

A

Reverse peristalsis in small intestine –> stomach and pylorus relaxation –> forced inspiration to increase abdominal pressure –> movement of larynx –> LES relaxation –> glottis closes –> forceful expulsion of gastric contents

44
Q

What coordinates the vomiting reflex?

A

medulla, nerve impulses transmitted by vagus and symp afferents to brain stem nuclei

45
Q

What allows the flow of contents from the SI into the LI?

A

Ileocecal junction
Distention of ileum cause relaxation of sphincter allowing for flow of contents from ileum into colon
Distention of colon causes contraction of sphincter preventing passage

46
Q

What muscles layers are found in the LI?

A

circular which is continuous from cecum to the anal canal

longitudinal= taeniae coli of 3 flats bands of longitudinal fibers that run from cecum to rectum

47
Q

What sphincters are found in the LI?

A

internal anal of smooth muscle and external of striated muscle

48
Q

What are haustras?

A

small pouches that give LI segmented appearance, not fixed

49
Q

What is the parasympathetic innervation of the LI?

A

Vagus for cecum ascending and transverse colon, pelvic nerves for sacral portion of spinal cord (S2-4), descending and sigmoid colon, rectum

50
Q

What is the sympathetic innervation of the LI?

A

(T10-L2)= superior mesenteric ganglion for proximal regions, inferior mesenteric ganglion for distal, and hypogastric plexus for distal rectum and anal canal

51
Q

What innervates the external anal sphincter?

A

Somatic pudendal nerve

52
Q

What are mass movements?

A

Occur in colon over large distances 1-3 times a day stimulating defecation reflex, final movement propels fecal content into the rectum

53
Q

What happens when the anal canal fills?

A

smooth muscle wall of the rectum contracts and internal sphincter relaxes= rectosphincteric reflex

54
Q

What controls the rectosphinteric reflex?

A

partially by ENS, reflex reinforced by activity of neurons within the spinal cord

55
Q

What happens in Hirschsprung’s disease?

A

ganglion cells absent from segment of colon –> VIP low –> SM constricts and loss of coordinated movements –> colon contents accumulate

cause difficulty in passing stool (congenital megacolon), failure to pass meconium, poor feeding, jaundice, vomiting

56
Q

What is the vago-vagal reflex?

A

long reflex, generally stimulatory –> increase motility secretomotor vasodilatory activities, vagus carries both aff and eff

57
Q

What is the intestino-intestinal reflex?

A

depends on extrinsic neural connections, inhibitory, if bowel grossly distended, contractile activity in rest of bowel inhibited

58
Q

What is the gastroileal reflex?

A

gastric distention relaxes ileocecal sphincter

59
Q

What is the gastro-duo-colic reflex?

A

distention of stomach/duo initiates mass movements, transmitted by ANS

GIGU (40 decks)

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