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COM - GI Final > Motility Of GI Tract - Lopez > Flashcards

Motility Of GI Tract - Lopez Flashcards

1
Q

When circular muscle contracts what happens?

A

Diameter decreases

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2
Q

When longitudinal muscle contracts what happens?

A

Length of segment decreases

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3
Q

Describe phasic contractions

A

Periodic contraction, followed by relaxation

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4
Q

What body parts use phasic contraction?

A

Esophagus, stomach (antrum), small intestine

ESS

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5
Q

Describe tonic contractions

A

Constant level of contraction, no relaxation

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6
Q

What body parts use tonic contractions?

A

Stomach (orad), lower esophagus, ileocecal, internal anal sphincters

SLEii

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7
Q

What are slow waves a unique feature of?

What are they not?

A

Smooth muscle

Action Potential

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8
Q

TRUE or FALSE: Subthreshold depolarization can produce contractions in GI smooth m.?

A

TRUE, but weak

Aka basal contractions

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9
Q

What neurotransmitter increases the amplitude of slow waves and # of APs?

Decreases?

A

ACh

NE

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10
Q

What else increases amplitude of slow waves and # of APs?

What else decreases?

A

Stretch, PS

Sympathetics

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11
Q

Where do slow waves originate?

A

Interstitial cells of Cajal (ICC)

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12
Q

How do slow waves spread through ICC to smooth m.?

A

Gap junctions

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13
Q

What are the 3 phases of swallowing and which are voluntary/involuntary?

A

Oral (V)
Pharyngeal (IV)
Esophageal (IV)

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14
Q

Describe the pharyngeal phase of swallowing

A

Soft palate pulled up -> epiglotis movies -> UES relaxes -> peristaltic wave initiated -> food propelled through open UES

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15
Q

What controls the esophageal phase of swallowing?

A

Swallowing reflex and ENS

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16
Q

Where is the swallowing center located?

A

Medulla

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17
Q

What nerves sense food in the pharynx?

A

Vagus and glossopharyngeal

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18
Q

What inhibits the respiratory center during the pharyngeal stage of swallowing?

A

Swallowing center

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19
Q

Describe the primary peristaltic wave

A

Continuation of pharyngeal peristalsis

Cannot occur after vagotomy

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20
Q

What does the secondary peristaltic wave do?

A

Occurs when primary wave fails to clear gastric contents
Induced by distention of esophagus
Involves swallowing center and ENS
Occurs after vagotomy

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21
Q

What nerve acts through the Myenteric nervous system?

This controls what part of the esophagus?

A

Vagus

Mid and lower regions

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22
Q

When does gastroesophageal reflux occur?

A

Intra-abdominal pressure is increased (due to pregnancy, obesity)

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23
Q

What is released to mediate opening of the LES for receptive relaxation?

A

VIP and possibly NO

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24
Q

What is GERD?

Symptoms?

Result?

A

Abnormal relaxation of the LES

Heartburn, chest pain, dysphagia, lump in throat

Barret’s, stricture, asthma, sinusitis

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25
Q

What is achalasia?

Cause?

Symptoms?

A

Impaired peristalsis or lack of LES relaxation during swallowing or elevation of LES resting pressure

Damage to nerves in esophagus or abnormal immune system response

Weight loss, regurgitation, dysphagia, vomiting, chest pain

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26
Q

What layers of muscles does the stomach have?

A

Circular
Longitudinal
Oblique

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27
Q

What happens in the orad region of the stomach during receptive relaxation?

What kind of reflex is this?

A

DEC pressure, INC volume

Vagovagal reflex

28
Q

What effect does CCK have on the stomach?

A

DEC contractions

INC gastric secretions

29
Q

What does phase lag do as the peristaltic wave approaches teh antrum of the stomach?

A

DECREASES

30
Q

What happens in the caudad region of the stomach to further mix and reduce particle size of stomach contents?

A

Retropulsion

31
Q

What factors INC AP and force of contractions in the stomach?

A

PS
Gastrin
Motilin

32
Q

What factors DECREASE AP and force of contractions?

A

Sympathetics
Secretin
GIP

33
Q

How does the rate of gastric emptying INCREASE?

A

DEC distensibility of the orad, DEC tone of the pylori so

INC peristaltic contractions of caudad
INC diameter and inhibition of segmenting contractions of prox duodenum

34
Q

What factors inhibit gastric emptying?

A

DEC peristaltic contractions

INC tone of pyloric sphincter

35
Q

What receptors inhibit gastric emptying via what hormone?

A

Fat and proteins via CCK (INC gastric distensibility)

36
Q

What does hypertonicity in the duodenum lead to?

A

Inhibition of gastric emptying

37
Q

What is the most common problem associated with disorders of gastric motility?

A

Slow gastric emptying

38
Q

What is gastroparesis?

Cause?

Symptoms?

A

Slow emptying of stomach/paralysis of stomach

Damage to the vagus nerve or high blood glucose

Nausea, vomiting, abdominal bloating, weight loss

39
Q

How are large particles of undigested residue in the stomach emptied?

How is this mediated and how often?

A

MMC

Via Motilin in 90 minute intervals

40
Q

Absence of MMCs in the stomach is assoc. with what?

A

Gastroparesis

41
Q

What does segmentation contractions do?

A

Mix the chyme and expose it to pancreatic enzymes

42
Q

What do peristaltic contractions do?

A

Propel the chyme towards large intestine

43
Q

What contracts behind the bolus?

In front of?

A

Circular

Longitudinal

44
Q

Describe initiation of contractions in the small intestine

A

Slow waves DO NOT initiate contraction
APs necessary
Slow wave freq. sets the max freq. of contractions

45
Q

What has a higher higher slow wave frequency:
Duodenum or ileum?

What is the general trend?

A

Duodenum (12 cycles/min)

DECREASE in freq. toward ileocecal junction

46
Q

What releases serotonin?

Where does it bind?

What does it initiate?

A

ECCs

Receptors in IPAN (intrinsic primary afferent neuron)

Peristaltic reflex (stimulates contractions)

47
Q

What hormones stimulate contractions of the intestine?

Inhibit?

A

PGs, Gastrin, CCK, Motilin, insulin

Epi, secretin, glucagon

48
Q

What coordinates the vomiting reflex?

A

Medulla

49
Q

Describe the order of events of reverse peristalsis in vomiting

A 
Reverse peristalsis of s.i.
Relaxation of stomach and pylorus
Force inspiration to INC abdominal pressure
Movement of larynx
Relaxation of LES
Closure of glottis
Forceful expiration of gastric contents
50
Q

What stimulates the chemical trigger zone in the vomiting reflex?

A

Morphines, opioids

51
Q

What relaxes the sphincter and excites peristalsis at the ileocecal junction?

A

Pressure and chemical irritation

52
Q

What inhibits peristalsis of ileum and excites sphincter at the ileocecal junction?

A

Pressure or chemical irritation in cecum

53
Q

What prevents passage of contents from the colon to the ileum?

A

Distention of the colon –> contraction of sphincter

54
Q

Main fx of l.i.?

A

Absorb water and Vits

Convert digested food into feces

55
Q

What portions of the Sympathetic N.S. Innervates the large intestine?

A

T10-L2

56
Q

What is the sympathetic innervation of the distal rectum and anal canal?

A

Hypogastric plexus

57
Q

What is the sympathetic innervation of the proximal large intestine?

A

SM ganglion

58
Q

What is the sympathetic innervation of the distal large intestine?

A

IM ganglion

59
Q

What is the sympathetic innervation of the external anal sphincter?

A

Somatic pudendal nerves

60
Q

What are the major excitatory mediators of the large intestine?

Inhibitory?

A

ACh and Substance P

NO and VIP

61
Q

Where do segmentation contractions occur?

Fx?

A

Cecum and ascending colon

Mix contents

62
Q

What do mass movements stimulate?

How often?

A

Defecation reflex, propels feces into rectum

1-3 times/day

63
Q

What does poor motility cause in large intestine?

Excess motility?

A

Greater absorption therefore hard stool –> constipation

Less absorption –> diarrhea

64
Q

Where do rectal distention senses and voluntary control of the external anal sphincter pathways travel to?

A

Spinal cord to cerebral cortex

65
Q

What is the rectosphincteric reflex under control of?

What happens in paraplegic patients?

A

Neural control

Lack tonic contractions, defecation

66
Q

What is diverticulitis?

What causes it?

Where is the most common location?

A

Small sacs of intestinal lining that bulge outward in a weak spot

Excess pressure in colon

Left side of colon

67
Q

What is motility important for?

A

Preparation of ingested food for digestion and absorption

COM - GI Final (5 decks)

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