GI Motility

Question 1

What are Slow Waves?

Answer 1

1. Basic electrical rhythm
2. Originate in Interstitial cells of Cajal (pacemaker)
   * Abundant in myenteric plexus
3. Frequency of slow waves

• Stomach: 4mins
• Duodenum: 12mins
• Distal Ileum: 8mins
• Cecum: 2mins
• Sigmoid: 6mins

Question 2

What are the steps of Peristalsis?

Answer 2

1. Gut lumen stretches by food bolus

• Releases Serotonin
  
  • Activates Myenteric plexus

2. Cholinergic neurons activate P and ACh in ORAL direction
   * Contraction of smooth muscle forms behind bolus
3. Cholinergic neurons in ANAL direction stimulate the secretion of NO, VIP, neuropeptide y, and ATP
   * Causes relaxation of the smooth muscle in front of the bolus

Question 3

What are the steps of Migrating Motor Complex? (MMC)

Answer 3

1. Contraction from distal stomach to distal ileum occurs
2. Clears intestinal lumen for next meal
   * Every 90 minutes
3. Loss of MMC causes bacterial overgrowth

Question 4

What are the Swallowing Centers?

Answer 4

1. Nucleus of TRACTUS SOLITARIUS
2. Nucleus AMBIGUUS

*Both located in medulla

• Somatosensory receptors carry information via Trigeminal, Glossopharyngeal, and vagus nerve

Question 5

What is Gastro-Esophageal Reflux Disease? (GERD)

Answer 5

1. Lower esophageal sphincter is incompetent
   * Regurgitation of gastric juices and content go back into esophagus
2. Symptoms

• Heartburn
• Sour taste
• Dysphagia
• Regurgitation

Question 6

What is Barret’s Esophagus?

Answer 6

1. Stratified squamous epithelium replaced by intestinal simple columnar epithelium with goblet cells
2. Can cause ADENDOCARCINOMA of lower esophagus

*Upper esophagus results in Squamous cell carcinoma

Question 7

What is Achalasia Cardia?

Answer 7

1. Degeneration of Myenteric plexus (Auerbach)

• Causing loss of Nitric Oxide
• Loss of Peristalsis in distal 2/3

2. Barium swallow (“bird’s beak” appearance)
3. Symptoms

• Dysphagia of solids and liquids
  
  • Absence of coordinated peristaltic effort down the esophagus
• Nocturnal regurgitation of food
• Can cause Esophageal Squamous Cell Carcinoma
• Increase tone in Lower esophageal sphincter

Question 8

What is Mallory-Weiss Tear?

Answer 8

1. Superficial longitudinal mucosal laceration of lower esophagus
2. Associated with

• Forceful retching (vomiting)
• Alcoholism
• Hiatal hernias

Question 9

What is Boerhaave’s syndrome?

Answer 9

1. Spontaneous rupture of distal thoracic esophagus
2. Seen in young people vomiting from alcohol
3. Serious complication of bulima

Question 10

What is the Antral systole?

Answer 10

1. Vigorous peristaltic rhythm

• Mix chyme
• Propel chyme through pylorus into duodenum

Question 11

What is Retropulsion?

Answer 11

1. Mix chyme with digestive enzymes
2. Chyme propelled from antrum of stomach back to body of stomach

Question 12

What is Gastroparesis?

Answer 12

1. Partial paralysis of stomach
   * Inability to empty food
2. Damage to vagus nerve
   * Disruption in digestive system
3. Symptoms

• Nausea
• Vomiting
• Abdominal fullness
• Gastroesophageal reflux
• Heartburn

*More difficult to control blood glucose levels in diabetics

Question 13

What neurotransmitters deal with Vomiting?

Answer 13

1. Serotonin
2. Dopamine

Question 14

What is Gastrocolic Reflex?

Answer 14

1. Food in stomach and chyme in duodenum stimulate mass movement
2. Enteric Nervous System (ENS) activates
3. Propels content toward rectum
4. Defecation
   * By stimulus of local and parasympathetic reflexes