GI 6 Flashcards
What are the two main functions of motility of the GI tract?
- The movement of contents from the mouth to the anus
* Mixing to facilitate digestion and absorption
What are the two patterns of motility?
- Peristalsis
* Segmentation
What is Peristalsis?
Rings of contraction that pass along the GI tract and force the contents along
What occurs in Segmentation?
There is constriction in alternating portions of the tract mixing content in specific portions
What causes peristalsis?
Peristalsis is a reflex response triggered by the luminal contents within the intestine stretching the wall
What occurs during the peristalsis reflex?
A food bolus stretches the intestinal wall causing a circular contraction behind the food bolus and relaxation in front of the food bolus
What is the Peristalsis reflex independant of?
It is independent of extrinsic innervation
What can peristalsis be modulated by?
Autonomic input
What does modulation of peristalsis by the autonomic nervous system do?
Adjust the strength
What is the Peristalsis reflex dependant on?
The integrated activity of the enteric nervous system
How does the Peristalsis reflex work?
Stretch response cause the release of serotonin. The Serotonin activates sensory neurons that activate the myenteric plexus. Upstream neurons release substance P and acetylcholine causing constriction. Downstream neurons release Nitric Oxide and VIP causing relaxation
What do the upstream neurons in peristalsis release and what does it do?
They release acetylcholine and substance P causing constriction
What do the downstream neurons in peristalsis release and what does it do?
They release nitric oxide and Vasoactive intestinal polypeptide which causes relaxation
Where does Segmentation primarily occur?
In the small intestine
