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GIGU > Motility of the GI Tract > Flashcards

Motility of the GI Tract Flashcards

(59 cards)

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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?

Study These Flashcards
A

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

25
What effect does CCK have on the orad region?
decrease contractions and increase gastric distensibility
26
What is the primary event of the caudad region of the stomach? Where is it the strongest?
Peristaltic contraction (mid stomach to pylorus) Increase in force and velocity as approach pylorus
27
What is retropulsion?
Propulsion of gastric contents back into the stomach for further mixing and reduction of particle size
28
What increases forces of contractions and APs?
parasympathetics gastrin motilin
29
What decreases APs and force of contractions?
sympathetics secretin GIP
30
What increases gastric emptying?
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
What decrease gastric emptying?
relaxation of orad (increase in distensibility) decrease force of peristaltic contractions increase tone in pyloric sphincter segmentation contraction in intestine
32
What is the entero-gastric reflex? What stimulates it?
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
What can cause slow gastric emptying? How can it be treated?
gastric ulcer, cancer, eating disorder, vagotomy pyloroplasty, balloon dilation
34
What is gastroparesis? What are the symptoms?
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
What happens when we fast? Why is this important?
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
What are segment contractions of the SI?
generate back and forth movements, produce no forward, propulsive movements
37
What are peristaltic contractions of the SI?
circular and longitudinal muscles work in opposition to complement each other, reciprocally innervated
38
Do slow waves initiate contractions in the SI?
NO APs/spike potentials necessary for muscle contraction to occur slow wave frequency sets max frequency of contractions (duo (12) >> jeju (10) >> ileum (8) )
39
What happens when the SI becomes distended?
Signals for the release of serotonin by enterochromaffin cells which bind to receptors in IPANs initiating peristaltic reflex
40
What stimulates contraction in the SI?
serotonin, prostaglandins, gastrin, CCK, motilin, and insulin
41
What inhibits contraction in the SI?
epi, secretin, and glucagon
42
What is the role of the myenteric and meissner/submucosal plexus in the SI?
myenteric= regulate relegation and contraction of intestinal wall meissner= sense lumen enviorment
43
What are the steps of the vomiting reflex?
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
What coordinates the vomiting reflex?
medulla, nerve impulses transmitted by vagus and symp afferents to brain stem nuclei
45
What allows the flow of contents from the SI into the LI?
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
What muscles layers are found in the LI?
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
What sphincters are found in the LI?
internal anal of smooth muscle and external of striated muscle
48
What are haustras?
small pouches that give LI segmented appearance, not fixed
49
What is the parasympathetic innervation of the LI?
Vagus for cecum ascending and transverse colon, pelvic nerves for sacral portion of spinal cord (S2-4), descending and sigmoid colon, rectum
50
What is the sympathetic innervation of the LI?
(T10-L2)= superior mesenteric ganglion for proximal regions, inferior mesenteric ganglion for distal, and hypogastric plexus for distal rectum and anal canal
51
What innervates the external anal sphincter?
Somatic pudendal nerve
52
What are mass movements?
Occur in colon over large distances 1-3 times a day stimulating defecation reflex, final movement propels fecal content into the rectum
53
What happens when the anal canal fills?
smooth muscle wall of the rectum contracts and internal sphincter relaxes= rectosphincteric reflex
54
What controls the rectosphinteric reflex?
partially by ENS, reflex reinforced by activity of neurons within the spinal cord
55
What happens in Hirschsprung's disease?
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
What is the vago-vagal reflex?
long reflex, generally stimulatory --> increase motility secretomotor vasodilatory activities, vagus carries both aff and eff
57
What is the intestino-intestinal reflex?
depends on extrinsic neural connections, inhibitory, if bowel grossly distended, contractile activity in rest of bowel inhibited
58
What is the gastroileal reflex?
gastric distention relaxes ileocecal sphincter
59
What is the gastro-duo-colic reflex?
distention of stomach/duo initiates mass movements, transmitted by ANS

GIGU (14 decks)

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