2.2 Myenteric vs Submucosal Plexus

• What does the myenteric plexus consist mostly of?

  A linear chain of interconnecting neurons
• Where does the myenteric plexus extend?

  Along the entire length of the gastrointestinal tract
• What is the primary function of the myenteric plexus?

  Controlling muscle activity along the gut
• What are the principal effects when the myenteric plexus is stimulated?

  Increased gut wall tone and contraction intensity
• What is one effect of stimulating the myenteric plexus?

  Increased tonic contraction of the gut wall
• What is another effect of stimulating the myenteric plexus?

  Increased intensity of rhythmical contractions
• What is a third effect of stimulating the myenteric plexus?

  Slightly increased rate of contraction rhythm
• What is a fourth effect of stimulating the myenteric plexus?

  Increased velocity of conduction of excitatory waves
• Why should the myenteric plexus not be considered entirely excitatory?

  Some neurons secrete inhibitory transmitters
• What is one possible inhibitory transmitter secreted by the myenteric plexus?

  Vasoactive intestinal polypeptide
• Which sphincter does the myenteric plexus inhibit to control stomach emptying?

  The pyloric sphincter
• What does the pyloric sphincter control?

  Emptying of the stomach into the duodenum
• Which sphincter controls emptying from the small intestine into the cecum?

  The sphincter of the ileocecal valve
• What is the main function of the submucosal plexus?

  Controlling function within the inner wall
• How does the submucosal plexus integrate sensory signals?

  It integrates signals from the gastrointestinal epithelium
• What local functions does the submucosal plexus help control?

  Local secretion, absorption, and contraction
• What is the relationship between the submucosal plexus and the myenteric plexus?

  The submucosal plexus controls inner wall functions, unlike myenteric
• What are the types of neurotransmitters secreted by enteric neurons?

  • Acetylcholine
  • Norepinephrine
  • Adenosine triphosphate
  • Serotonin
  • Dopamine
  • Cholecystokinin
  • Substance P
  • Vasoactive intestinal polypeptide
  • Somatostatin
  • Leu-enkephalin
  • Met-enkephalin
  • Bombesin
• What is the primary effect of acetylcholine on gastrointestinal activity?

  It most often excites gastrointestinal activity
• What is the effect of norepinephrine on gastrointestinal activity?

  It almost always inhibits gastrointestinal activity
• How does epinephrine affect gastrointestinal activity?

  It inhibits gastrointestinal activity via the blood
• What can be said about the other neurotransmitter substances mentioned?

  They are a mixture of excitatory and inhibitory agents
• What are the characteristics of neurotransmitters in the enteric nervous system?

  • Acetylcholine: Excites activity
  • Norepinephrine: Inhibits activity
  • Epinephrine: Inhibits activity via blood
  • Other substances: Mixture of excitatory and inhibitory