When does MMC begin?
3-4 hours after a meal
where is the MMC active?
mid stomach through the terminal ileum
what is the purpose of the MMC?
- housekeeping, sweeps undigested food and bacteria into colon - preventing bacterial growth and damage to villus lining of SI (easy to damage)
What stimulates phase 3?
What happens secondary peristalsis?
Stuck food initiates the enteric system to increase secretions and peristalsis
2 types of propulsion involved in swallowing?
Primary and secondary esophageal Peristalsis
What stimulates the stomach into a relaxed state to accept food?
What else does vegal stimulation do to the stomach beside relaxation?
induces gastric juice secretion
Why function does the narrowing of the antrum have?
- enables some mixing and mechanical digestion of chyme (breaks it up). Ensures that food particles are small enough to enter duodenum
what is the usual resting potential of muscles in the intestines?
What are the types of food that take the longest to clear the stomach?
high acidic meals, then lipids
What is the underlying nerve function that controls the rate of contraction in GI tract?
Resting memb potential in the form of slow waves
rate of slow waves in the stomach?
every 20 seconds * contractions are most likely in stomach than in SI or colon
rate of slow waves in the ilium?
12 per minute
what is the action potential threshold ?
Frequency of slow waves in the colon?
1 every 3 hours
What type of nerve stimulation induces depolarizaiton?
What controls the force of contraction?
level of depolarization, NOT the slow waves more depolarization above -40, more APs more depolarized AP = stronger contractions
What hormone induces depolarization?
What functions does gastrin have?
Depolarization of smooth muscles, stimulates HCl secretion
What secretes Gastrin and where are they located?
G cell in the antrum and duodenum
What are the things that help depolarize the GI muscles?
stretch receptors, parasympathetics, gastrin, seratonin, substance P/tachykinin
What hyperpolarizes smooth muscles in the GI?
NE, sympathetics, VIP, NO
Another name for substance P
What does aborally mean?
away from the mouth
What is the function of segmentation?
movement and mixing of chyme
What 2 things stimulate peristalsis?
stretch and parasympathetics
during peristalsis, what happens to the muscles behind and ahead the bolus?
behind bolus: muscles get depolarized - contract ahead of bolus: muscles get hyper-polarized - relax
Under what control is segmentation?
What two controls initiate contraction of the gall bladder?
CCK and vegal stimulation
What is the sphincter called at the bottom of the bile duct?
sphincter of oddi
What stimulates the relaxation of the sphincter of Oddi?
What are the longitudinal muscles that propel chyme through the large intestine?
What are mass movements? Cause?
- Periods of hyperpolarization/relaxation in the colon followed by strong peristaltic contractions (making feces to make room for new food) - caused by gastrin and vegal stimulation
What is the reflex that induces mass movements?
Gastrocolic reflex - eating more food, trying to push out digested food in colon
What is hirshprung's disease?
Inability to relax the internal rectal sphincter, which leads to megacolon
How can fever or hyperthyroidism cause diarrhea?