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GI Exam 1 > Motility of the GI Tract > Flashcards

Motility of the GI Tract Flashcards

1
Q
  • Function of the circular muscle of the GI tract
  • Function of the longitudinal muscle of the GI tract
A
  • Decrease diameter of segment
  • Decrease length of segment
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2
Q
  • What are slow waves?
A
  • Depolarization and repolarization of membrane potential
  • NOT AN AP (an AP occurs only when the depolarization of slow wave reaches threshold)
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3
Q
  • Phasic contractions
  • Tonic contractions
A
  • Phasic contractions
    • ​Periodic contractions followed by relaxation
  • Tonic contractions
    • ​ Constant level of contraction without regular periods of relaxation
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4
Q
  • Where are phasic contractions common?
A
  • Esophagus
  • Stomach (antrum)
  • Small intestine
  • All tissues involved in mixing and propulsion
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5
Q
  • Where are tonic contractions common?
A
  • Stomach (orad)
  • Lower esophageal sphincter (LES)
  • Ileocecal Valve
  • Internal anal sphincter
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6
Q
  • What type of contraction is shown?
A
  • Tonic
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7
Q
  • What type of contraction is shown below?
A
  • Phasic
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8
Q
  • What is the relationship between slow waves, APs and contractions in the smooth muscle?
A
  • The greater the number of APs on top of the slow wave, the larger the muscle contraction
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9
Q
  • What NTX increases the amplitude of slow waves (depolarize)
  • What NTX decreases the amplitude of slow waves (hyperpolarize)
A
  • ACh (also stretch and parasympathetics)
  • NE (and sympathetics)
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10
Q
  • The _ plexus controls GI secretions and local blood flow
  • The _ plexus controls GI movements
  • _ in both plexuses generate spontaneous slow wave activity
A
  • Submucosal
  • Myenteric (Auerbach)
  • Pacemaker regions
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11
Q
  • What cells are responsible for generating and propagating slow waves in the GI tract?
  • How do these slow waves spread to the smooth muscle cells?
  • Electrical activity drives the _ of contraction
A
  • ICC (Interstitial Cells of Cahal)
  • Gap junctions
  • Frequency
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12
Q
  • What nerve innervates the muscles of mastication
  • What area of the brain is responsible for controlling mastication?
  • Mastication is caused by a _ reflex
A
  • Motor branch of CN V
  • Brainstem nuclei
  • Chewing
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13
Q
  • What are the three phases of swallowing?
  • Which phases are voluntary?
  • Which phases are involuntary?
  • What area of the brain controls the involuntary swallowing reflex?
A
  • Oral phase, Pharyngeal phase, Esophageal Phase
  • Voluntary
    • Oral Phase
  • Involuntary
    • Pharyngeal phase
    • Esophageal phase
  • Medulla
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14
Q
  • Describe the pharyngeal phase of the swallowing reflex
A
  • Soft palate pulled up
  • Epiglottis moves
  • UES relaxes
    Peristaltic wave of contractions initiated in pharynx
  • Food propelled thru oppen UES
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15
Q
  • Describe the esophageal phase of the swallowing reflex
A
  • Controlled by swallowing reflex and the ENS
  • Primary (1) peristaltic wave
  • Secondary (2) peristaltic wave
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16
Q
  • Describe the involuntary swallowing reflex
A
  • Food in pharynx sensed by afferent sensory neurons (vagus/glossopharyngeal)
  • Signals sent to the swallowing center
  • To brainstem nuclei
  • Efferent input to the pharynx
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17
Q
  • Primariy peristaltic wave
  • Unable to occur after which procedure?*
A
  • Continuation of pharyngeal peristalsis
  • Controlled by medulla
  • Vagotomy
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18
Q
  • Secondary Peristaltic Wave:
    • When does it occur?
    • What structures are involved?
    • Can occur in absence of _
    • Can still occur after what procedure?
A
  • Occurs if primary wave fails to empty the esophagus or if the gastric contents reflux into the esophagus
  • Medulla and ENS
  • Oral and pharyngeal phase
  • Vagotomy
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19
Q
  • Which pressure is more subatmospheric: thorax or abdomen?
A
  • Thorax
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20
Q
  • Achalasia
A
  • Impaired peristalsis
  • Incomplete LES relaxation during swallowing (causes backup of food)
  • Elevation of LES resting pressure
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21
Q
  • What causes achalasia?
A
  • Lack of VIP
  • ENS has been knocked out
  • Damage to nerves in the esophagus
  • Can result in:
  • Regurgitation
  • Dysphagia
  • Chest Pain
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22
Q
  • What causes GERD?
  • What occurs anatomically?
  • What can result?
A
  • Motor abnormalities that result in abnormally low pressures in the LES (if intragastric pressure increases: large meal, heavy lifting, pregnancy)
  • LES relaxes abnormally or weakens
  • Backwash of acid, pepsin, bile into the esophagus
  • Heartburn, acid regurg
  • Esophagitis, Stricture of esophagus, Barrett’s Esophagus
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23
Q

Function of the orad of the stomach (contains fundus and proximal portion of the body of the stomach)

​​

A
  • Receptive relaxation
  • Decreased pressure and increased volume of the orad region
  • Vagovagal reflex
  • CCK can decrease contractions and increase gastric distensibility
24
Q
  • Function of the caudad region of the stomach (contains the distal portion of the stomach and the antrum)
A
  • Mix and digestion
  • Peristaltic contractions (mid stomach to pylorus)
  • Contractions increase in force and velocity as they approach the pylorus
  • Max frequency is 3-5 waves/min
  • PHASE LAG DECREASES AS PERISTALTIC WAVE APPROACHES THE ANTRUM
25
Q

Waves of contraction close the _ sphincter and gastric contents are retropulsed back into stomach for further mixing

A
  • Pyloric
26
Q
  • Effects of parasympathetic stimulation, gastrin and motilin on gastric contractions
  • Effects of sympathetic stimulation, secretin and GIP on gastric contractions
A
  • Increase AP and force of contractions
  • Decrease AP and force of contractions
27
Q
  • How long does gastric emptying take?
A
  • 3 hours
28
Q
  • What factors increase the rate of gastric emptying?
A
  • Decreased distensibility of the orad
  • Increased force of peristaltic contractions of caudad stomach
  • Decreased tone of pylorus
  • Increased diameter and inhibition of segmenting contractions of proximal duodenum
29
Q
  • Factors that inhibit gastric emptying?
A
  • Increased distensibility of the orad
  • Decreased force of peristaltic contractions in the caudad
  • Increased tone of the pyloric sphincter
  • Segmentation contractions in the intestine (shuts pyloric sphincter to limit gastric contents that enter the duodenum)
30
Q
  • Entero-Gastric Reflex
A
  • Negative feedback from the duodenum will slow down the rate of gastric emptying
    • ​Acid in the duodenum stimulates secretin release and inhibits stomach motility via inhibition of gastrin
    • Fats in the duodenum stimulate CCK and GIP which inhibit stomach motility
    • Hypertonicity in the duodenum act on unknown hormone to inhibit gastric emptying
31
Q
  • What conditions can slow gastric emptying?
  • Symptoms?
  • Treatment?
A
  • Gastric ulcer, cancer, eating disorders, vagotomy
  • Fullness, loss of appetite, nausea, sometimes vomiting
  • Pyloroplasty, Balloon DIlation
32
Q
  • Gastroparesis
A
  • Slow emptying of stomach/paralysis of stomach in absence of mechanical obstruction
  • Can be caused by:
    • Diabetes Mellitus
    • Damage to the Vagal Nerve
  • Symptoms:
    • Nausea
    • Vomiting
    • Fullness after early eating
    • Weight loss
    • Abdominal Bloating
    • Abdominal Pain
33
Q
  • What is the function of the Migrating Myoelectic Complex (MMC)?
  • What peptide mediates the MMC?
  • When is the MMC inhibited?
A
  • Empties large particles of undigested residues that remain in the stomach
  • Periodic bursting peristaltic contractions that occur every 90 minutes
  • Motilin
  • Feeding
34
Q
  • What two types of contractions are present in the small intestine?
  • What is the function of each?
A
  • Segmental contraction
    • ​Generates back and forth movemetns
    • Produces no forward, propulsive movement along the small intestine
  • Peristaltic contractions
    • ​Circular and longitudinal muscles work in opposition and complement each other’s actions
    • Are reciprocally innervated
35
Q
  • Do slow waves initiate contractions in the small intestine?
A
  • NO
36
Q
  • _ are necessary for APs in the small intestine to occur
  • _ frequency sets the maximum frequency of contractions
A
  • Spiked Potentials
  • Slow wave frequency
37
Q
  • What is the slow wave frequency gradient for:
    • Duodenum
    • Jejunum
    • Ileum
A
  • Duodenum: 12 cycles/min
  • Jejunum: 10 cycles/min
  • Ileum: 8 cycles/min
38
Q
  • *_ is released by enterochromaffin cells and binds to receptors in _, initiating the peristaltic reflex*
A
  • Serotonin (5-HT)
  • IPANs (intrinsic primary afferent neuron)
39
Q
  • Excitatory motor neurons release _ or _ and cause _
  • Inhibitory motor neurons release _ or _ and cause _
A
  • Excitatory:
    • ACh
    • Substance P
    • Contraction
  • Inhibitory
    • Substance P
    • NO
    • Relaxation
40
Q

The _ plexus regulates relaxation and contraction of the intestinal wall

The _ plexus senses the luminal environment

A
  • Myenteric
  • Submucosal (Meissner)
41
Q

Which factors stimulate intestinal contraction?

A
  • Serotonin
  • Prostaglandins
  • Gastrin
  • CCK
  • Motilin
42
Q

Which factors inhibit intestinal contractions

A
  • Epinephrine from adrenal glands
  • Secretin
  • Glucagon
43
Q
  • What area of the brain controls the vomiting reflex?
  • Nerve impulses are sent from _ and _ afferents to brainstem nuclei
  • What types of drugs can trigger the vomiting center in the brain?
A
  • Medulla
  • Vagus and sympathetic
  • Morphine, apomorphine
44
Q
  • Events of the vomiting reflex
A
  1. Reverse peristalsis in SI
  2. Stomach and pylorus relaxation
  3. Forces inspiration to increase abdominal pressure
  4. Movement into larynx
  5. LES relaxation
  6. Glottis closes
  7. Forceful expulsion of gastric contents
45
Q
  • Flow of contents from SI to LI is regulated at the _ junction
  • Distension of the _ causes relaxation of the ileocecal sphincter (allows contents to go from SI to LI)
  • Distension of the _ causes contraction of the ileocecal sphincter (prevents passage of contents from SI to LI)
A
  • Ileocecal
  • Ileum
  • Colon
46
Q
  • The longitudinal muscle layer of the large intestine forms _
  • These run from the cecum to the rectum
  • _ are small puches that give the large intestine its segmented appearance (not fixed)
A
  • Taeniae coli (3 flat bands of longitudinal fibers)
  • Haustras
47
Q
  • What are the main innervations of the large intestine?
A
  • ENS
    • Innervates inner circular and outer longitudinal layers of the muscularis externa
  • Parasympathetics
    • Vagus: Cecum, ascending and transverse colon
    • Pelvic nerves: Sacral portion of the spinal cord (S2-S4), Descending and sigmoid colon, rectum
  • Sympathetics
    • Superior mesenteric ganglion: proximal regions
    • Inferior mesenteric ganglion: distal regions
    • Hypogastric plexus: distal rectum and anal canal
  • Somatic pudendal nerves-external anal sphincter
48
Q
  • Mass movements occur in the LI _ times/day
  • This stimulates the _ reflex
  • Final mass movement propels fecal content into the _
  • Poor mobility causes _ absorption of water and _ feces (can lead to constipation)
  • Excess mobility causes _ absorption of water and _ feces (can lead to diarrhea)
A
  • 1-3
  • Defecation
  • Rectum
  • Increased, hard
  • Decreasedm soft
49
Q
  • Retrosphincteric reflex
A
  • As the rectum fills with feces, the smooth muscle contracts (ENS) and internal anal sphincter relaxes
  • Reflex is reinforced by neurons within spinal cord
  • The external anal sphincter, on the other hand, is tonically closed (and under voluntary control)
  • Sensation of rectal distension and voluntary control of the external anal sphincter are mediated by pathways within the spinal cord that lead to the cerebral cortex (Destruction of these pathways causes loss of voluntary control of defecation)
50
Q
  • Hirschprung’s Disease (was included like 3 times, so would definitely know this)
    • Cause:
    • Result:
    • Treatment
A
  • Ganglion cells absent from segment of colon
  • VIP levels are low; SM contraction, loss of coordinated movement; colon contents accumulate
  • Usually present at birth:
    • Failure to pass meconium
    • Poor feeding
    • Jaundice
    • Vomiting
    • Constipation
    • Swollen Belly
    • Malnutrition
  • Treatment:
    • Surgical resection of the colonic segment lacking ganglia
51
Q

Vago-vagal reflex (long reflex)

A
  • Generally stimulatory, increases motility, secretomotor and vasodilatory activities
  • Vagus carries both afferents (75%) and efferents (25%)
52
Q
  • Intestino-intestinal reflex
A
  • Depends on extrinsic neural connections
  • Generally inhibitory
53
Q
  • Enterogastric reflex
A
  • Negative feedback from duodenum slows rate of gastric emptying
54
Q
  • Gastroileal reflex (gastroenteric)
A
  • Gastric distension releases ileocecal sphincter
55
Q
  • Gastro and duodeno-colic reflexes
A
  • Distension of stomach/duodenum inititates mass movements
  • Transmitted by way of the ANS
56
Q
A

GI Exam 1 (10 decks)

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