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GI-Final > Motility Of The GI Tract-1/21/16 > Flashcards

Motility Of The GI Tract-1/21/16 Flashcards

1
Q

Phasic contractions are found where?

Tonic contractions are found where?

A

Phasic-Esophagus, stomach (antrum), SI, all tissues involved in mixing and propulsion

Tonic-Stomach (orad), lower esophagus, ileocecal and internal anal sphincters

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2
Q

List 3 stimuli for depolarization of slow waves to generate an AP

List 2 stimuli for hyperpolarization of slow waves that result in no AP

A

Depolarization–> 1) stretch, 2) Ach, 3) Parasympathetics

Hyperpolarization –> 1) Norepi, 2) Sympathetics

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3
Q

This functional layer consists of smooth muscle, its contractions change the surface area and shape of the epithelium:

These functional layers are made of smooth muscle and provide motility to the GI tract:

A

Muscularis mucosae

Muscularis propria or externa

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4
Q

This ENS plexus mainly controls GI secretion and local blood flow:

This ENS plexus is between longitudinal and circular layers and mainly controls GI movements:

A

Submucosal

Myenteric (Auerbachs)

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5
Q

Where do slow waves originate?

How do slow waves spread rapidly to smooth muscle?

A

Interstitial Cells of Cajal (ICC)

Via GAP JUNCTIONS

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6
Q

What are the 3 phases of swallowing?

A

Oral phase (Voluntary)–> Initiates swallowing process

Pharyngeal phase (involuntary) --> passage of food through pharynx into esophagus
Soft palate pulled upward --> epiglottis moves --> UES relaxes --> peristaltic wave of contractions is initiated in the pharynx --> food is propelled through open UES

Esophageal phase (involuntary) –> passage of food from pharynx to stomach; controlled by the swallowing reflex and the ENS (primary and secondary peristaltic waves)

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7
Q

Where is the swallowing center located?

A

The medulla

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8
Q

Diagram the neural circuit involved the in the swallowing reflex:

A

Food in pharynx –> AFFERENT sensory input via CN VII/IX –> Swallowing center (medulla) –> brain stem nuclei –> EFFERENT input to pharynx

The swallowing center inhibits the respiratory center during the pharyngeal stage

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9
Q

The primary peristaltic wave is a continuation of pharyngeal peristalsis, is controlled by the ____ and cannot occur after a ___

A

Medulla, Vagotomy

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10
Q

A secondary peristaltic wave occurs if primary contraction fails to empty the esophagus or when gastric contents reflux into the esophagus. It is induced by distention of the esophagus itself by the retained food, repeats until the bolus is cleared, both swallowing center and ENS are involved, can occur in the absence of ____ and occurs even after a ____

A

Oral and pharyngeal phases, Vagotomy

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11
Q

What type of muscle is found in the pharynx and UES?

What type of muscle is found in the rest of the esophagus, LES, and stomach?

A

Striated

Smooth

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12
Q

What are the UES and LES doing between swallows? What about the body of the esophagus?

Describe the pressure in the UES compared to the pharynx and body of esophagus between swallows:

A

They are both CLOSED

Body of esophagus is flaccid

UES Pressure > pharynx and body of esophagus pressure

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13
Q

What does the UES do during swallowing?

What does the body of the esophagus do during swallowing?

What does the LES and upper part of stomach do during swallowing?

A

UES relaxes (opens)=Low pressure

Body of esophagus undergoes peristaltic contraction=High pressure

LES and upper part of stomach relaxes=Low pressure

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14
Q

After a food bolus enters the stomach, the LES ____

A

Contracts (Increase pressure)

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15
Q

An abnormal relaxation of the LES as well as heartburn, chest pain, dysphagia, food regurgitation, a “lump” in the throat, and dry cough may indicative of ___

A

GERD

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16
Q

Achalasia is a neurogenic esophageal motility disorder characterized by impaired peristalsis and a lack of LES relaxation during swallowing. WHat are some causes of Achalasia?

A

Lack of VIP or the Enteric NS has been knocked out

Results from damage to nerves in the esophagus, preventing it from squeezing food into the stomach

May be caused by an abnormal IS response

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17
Q

Receptive relaxation occurs in the ___ region of the stomach

The function of receptive relaxation is to ____

Receptive relaxation is a ____ reflex

A

Orad

Receive the food bolus in the stomach: Decrease pressure, Increase the volume of the orad region

Vagovagal

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18
Q

Contractions of the ___ region of the stomach serve to both mix and propel gastric contents

A

Caudad

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19
Q

____ regulates gastric contractions by increase AP’s and the force of contractions

____ regulates gastric contraction by decreasing AP’s and the force of contractions

A

Parasympathetic stimulation, gastrin, motilin

Sympathetic stimulation, secretin, GIP

20
Q

The rate of gastric emptying increases by (increase or decrease):
___ distensibility of the orad
___ force of peristaltic contractions of the caudad stomach
___ tone of the pylorus
___ diameter and inhibition of segmenting contractions of the proximal duodenum

A

Decreased
Increased
Decreased
Increased

21
Q

What are factors that inhibit gastric emptying?

A
  • Relaxation of orad
  • Decreased force of peristaltic contractions
  • Increased tone of pyloric sphincter
  • Segmentation contractions in intestine
22
Q

Complete the last step in the following pathways:

Acid in duodenum –> Stimulates secretin release —> ?

Fats in duodenum –> Stimulates CCK and GIP –> ?

Hypertonicity in duodenum –> (unknown hormone) –> inhibit ___

A

Acid in duodenum –> stimulates secretin release –> INHIBIT STOMACH MOTILITY VIA GASTRIN INHIBITION

Fats in duodenum –> stimulate CCK and GIP –> INHIBIT STOMACH MOTILITY

Hypertonicity in duodenum –> (unknown hormone) –> INHIBIT GASTRIC EMPTYING

23
Q

___ is a slow emptying of the stomach/paralysis of the stomach caused by damage to the vagus nerve.

A

Gastroparesis –> Type I diabetes at risk and can be caused by High blood glucose (diabetic gastroparesis)

24
Q

Large particles of undigested residue remaining in the stomach are emptied by ___

A

Migrating Myoelectric Complexes (MMC)

25
Q

MMC’s are mediated by this hormone ___

Absence of MMCs in the stomach has been associated with this disorder ___

A

Motilin

Gastroparesis

26
Q

Describe what circular muscle and longitudinal muscle do BEHIND THE BOLUS during peristalsis:

Describe what circular muscle and longitudinal muscle do IN FRONT OF THE BOLUS during peristalsis

A

Behind the bolus–> Circular muscle CONTRACTS, Longitudinal muscle RELAXES

In front of the bolus –> Circular muscle RELAXES, Longitudinal muscle CONTRACTS

27
Q

How does the Slow Wave frequency gradient change along the SI?

A

There is a decrease in frequency toward the iliocecal junction

Duodenum=12 cycles/min
Jejunum=10 cycles/min
Ileum=8 cycles/min

28
Q

An excitatory motor neuron can cause peristaltic contractions in the SI with ___

An inhibitory motor neuron can inhibit peristaltic contractions in the SI with ___

A

Ach and Substance P –> cause contraction

VIP and NO -> Cause relaxation

29
Q 
Describe the actions of the following hormones as they relate to contractions of the intestine:
A) Serotonin
B) Prostaglandins
C) Epinephrine
D) Gastrin, CCK, motilin, and insulin
E) Secretin and glucagon
A

A) Serotonin –> stimulates contractions
B) Certain PGs–> stimulates contractions
C) Epi–>inhibits contractions
D) gastrin, cck, motilin, insulin–>tend to stimulate contractions
E) Secretin and glucagon –> tend to inhibit contractions

30
Q

The vomiting reflex is coordinated by the ___

A

Medulla

31
Q

Describe the order of events in REVERSE PERISTALSIS of the vomiting reflex:

How are nerve impulses trasnmitted in the vomiting reflex?

A

Reverse peristalsis in the SI –> Relaxation of stomach and pylorus –> forced inspiration to increase abdominal pressure –> movement of larynx –> relaxation of LES –> Closure of the glottis –> Forceful expulsion of gastric contents

By both Vagal and Sympathetic Afferent nerve fibers to multiple distributed nuclei in the brain stem

32
Q

Distention of the ileum causes ___ of the ileocecal sphincter

Distention of the colon causes ___ of the iliocecal sphincter

A

Relaxation-Allows flow of contents from the ileum into the colon

Contraction-Prevents passage of contents from the colon to the ileum

33
Q

The internal anal sphincter is composed of ____ muscle

The external anal sphincter is composed of ____ muscle

A

Smooth

Striated

34
Q

Where is the Myenteric plexus located in the LI?

List the main Parasympathetic innervation of the LI:

List the main Sympathetic innervation of the LI:

A

Concentrated beneath teneae coli, innervates muscle layers

Vagus n.–> cecum, ascending and transverse colon
Pelvic splanchnic nerves (S2-S4)–> descending and sigmoid colon, rectum

Superior mesenteric ganglion–> Proximal regions
Inferior mesenteric ganglion –> distal regions
Hypogastric plexus–> distal rectum and anal canal
Somatic pudendal nerves –> external anal sphincter

35
Q

____ occur in the cecum and ascending colon, cause little propulsion, and serves to mix the contents of the LI

A

Segmentation contractions

36
Q

___ occur in the colon, over large distances such as from the transverse colon to sigmoid colon, occurs 1-3 times/day and move the contents of the LI and stimulate defecation reflex.

A

Mass movements

37
Q

Fluid to semi-fluid is found in the ___ of the LI

Mush is found in the ___ of the LI

Semi-mush to semi-solid is found in the __ of the LI

Solid is found in the __ of the LI

A

Ascending colon

Transverse colon

Descending colon

Rectum

38
Q

___ motility causes greater absorption, and hard feces in transverse colon cause constipation

___ motility causes less absorption and diarrhea or loose feces

A

Poor

Excess

39
Q

In paraplegic patients lacking tonic contraction of the external anal sphincter, the ___ reflex results in defecation

A

Rectosphincteric

40
Q

The sensation of rectal distention, as well as the voluntary control of the external anal sphincter, is mediated by pathways within the spinal cord that lead to the ____

A

Cerebral cortex–> destruction of these pathways causes a loss of voluntary control of defecation

41
Q

___ contraction decreases the diameter of the segment

___ contraction decreases the length of the segment

A

Circular muscle

Longitudinal

42
Q

This long reflex is generally stimulatory and increases motility, is secretomotor, and has vasodilatory activities

A

Vago-vagal reflex–> vagus carries both afferents (75%) and efferents (25%)

43
Q

This short reflex is generally inhibitory, involving only the ENS and completely independent of the ANS

A

Intestino-intestinal reflex –> Ileocecal sphincter acts by this reflex and Atropine has no effect on it

44
Q

___ reflex is when negative feedback from the duodenum will slow down the rate of gastric emptying

A

Enterogastric

45
Q

___ reflex is when gastric distention relaxes the ileocecal sphincter

A

Gastroileal (gastroenteric)

46
Q

Gastrocolic and gastroduodenal reflexes are when distention of the stomach/duodenum initiate mass movements and are transmitted by way of the ___ nervous system

A

Autonomic

47
Q

___ reflex initiates defecation and is caused by rectal distention

A

Rectosphincteric

GI-Final (9 decks)

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