GI Tract Motility

What are the muscle functions in the gut?

to move, mix, and chop

Where is bolus found along the gastrointestinal tract?

from mouth to stomach

Where is chyme found along the gastrointestinal tract?

from stomach through small intestine

Where is fecal matter found along the gastrointestinal tract?

through large intestine

What are the two layers of smooth muscle within the tunica muscularis of GI?

inner circular (ring around lumen to constrict and relax) and outer longitudinal (along length to shorten like a slinky)

What is the myenteric nerve plexus?

ANS cell body for enteric innervation

What is the function of the myenteric plexus?

gut motility, help of pacemaker and interstitial cells

What are the functions of the submucosal plexus?

sensory, secretory, and regulates blood flow

What is peristalsis?

movement (faster)

What is segmentation?

mixing (slower)

What is the process of peristalsis?

the inner circular smooth muscle contracts behind the bolus to push while it relaxes around it the bolus to accept the movement, longitudinal contraction will help with propulsion (slinky)

How is contraction oral to the bolus stimulated?

neurotransmitters ACh and substance P

How is relaxation aboral to the bolus stimulated?

nitric oxide and vasoactive intestinal peptide

What is the process of segmentation?

contractions isolate small sections of intestine, moving their contents back and forth which continuously subdividing and mixing contents to allow all to reach mucosa for absorption of nutrients, minimal longitudinal contraction needed during this

What are slow waves?

initiated by pacemaker cells and spread to adjacent smooth muscle cells via gap junctions to partially depolarize and cause minor contraction of smooth muscle; coordinated the rhythmic GI motility

True or false: Slow waves are action potentials

false

Electric membrane potential in GI smooth muscle cells are ____ stable, rhythmically _______.

not, fluctuate

What is a spike potential?

true action potentials that occur thats to slow waves setting the basal pace

What is the migrating motor complex?

intestinal housekeeping waves causing giant migrating contraction that sweep undigested material down during fasting (2-3 hours after a meal) and occur every 90-120 minutes