Gi motility and Regulation [3] Flashcards
what is the predominant motor activity in the intestine that ensures proper digestion and absorption?
What about movement that results in net propulsion of contents
Segmentation
-mixing w/o propulsion
Peristalsis
- propulsive: contraction of adjacent segments occuring in coordinated manner
- contractile ring moves toward food bolus
Basic electrical rhythm (BER)
- describe
- would depolarization of BER alone cause contraction?
cyclic change in membrane polarization of sm cells
- slow waves → pulsatile
- consists of upstroke depolarization, partial repolar, and plateau potential
Would depolarization of BER alone cause contraction?
Which is lower in freq, stomach BER or duodenal BER?
- no: ACh needs to be added to cause threshold ot be reached (due to Ca2+ influx)
- stomach BER is lower bc you want distal ends to be moving faster (or else back log)
3 stages of swallowing
- voluntary or involuntary?
- Voluntary
- oral cavity → tongue push bolus → oropharynx - Pharyngeal phase
- involuntary: glottis over trachea
- UES relax - Esophageal phase
- involuntary: esophageal peristalsis
Mech of esophageal motility
UES: allows bolus to enter esophagus Esophageal peristaltic waves: - push bolus to LES in 5 sec. - just before bolus arrives, LES relaxes LES: relaxes so bolus → stomach - prevents reflux into esophagus - gatekeeper
Failure of LES to relax due to dmg/loss of enteric n. of LES
Achalasia → dysphagia
describe how the stomach stores food
- what about P concerns?
Accomodation
- regulated by vagus n.
Receptive relaxation
Allows fundus to accomodate/store fr. 1.5L → 3-4L w/o increase in intra-gastric P
Motility roles of stomach
mixing/churning with retropulsion and receptive relaxation
peristaltic spurts pushes sm amt of chyme pass pyloric sphincter
- another wave pushes rest of chyme back + break up food further into smaller pieces
Will the rate of gastric emptying increase or decrease with more food?
rate is increased due to gastric distension →
increase stretch →
peristalsis increase (vagal + myenteric reflexes)
Gastrin is also secreted in response to food → increase peristalsis and decrease pyloric tone
Key hormones secreted by Small intestines
CCK
Secretin
GIP (gastrointestinal peptide)
MMC occurs only during ____ and is terminated by ____.
It is initiated when____.
- phases?
fasting, eating
Activated when motilin is released by small intestine
- sweeping process every 90-100 min
- 40-60% of 90 min duration
Phase I: quiescence occurs for 40-60% of the 90 min
Phase II: motility ↑s, but w/ irregular contractions
- fails to propel content
- 20-30% of MMC duration
Phase III: from body → pylorus → duodenum → ileocecal valve
- 5-10 min of intense contractions
Main fxn of large intestines
- how many types of motility?
reabsorb water and ions
- two types of motility
1. haustration
2. mass movements
- haustration vs
- mass movements
of Large intestines
- haustration: muscles of colon wall are contracted intermittently to divide colon into fxnal segments, “haustra”
- mix and dry chyme - mass movements: “giant migrating contractions”
unique to Lg intestines
- Slow intense + prolonged peristalsis contractions (propel chyme)
- strips area of LI clear of contents
- segmental activity stop temp, + loss of haustration
Gastroileal reflex
- mediated by which nerves?
stomach activity stimulates movement of chyme thru ileocecal sphincter → LI
- mediated by enteric nerves
Gastrocolic reflex
- mediated by which nerves?
Food in stomach stimulates mass movement in colon
- mediated by enteric nerves
