Physio GI Motility (32)

Card Set Information

Physio GI Motility (32)
2014-04-09 18:28:14
MBS Physiology
Exam 3
Show Answers:

  1. 31 Taste/Bicarb/Saliva
  3. What is the taste we’re most sensitive to?
    • BITTER
    • taste buds are composed of groups of between 50 & 150 columnar taste receptor cells bundled together
  4. Supertaster
    roughly 1 in 4 people is a that is several times more sensitive to bitter & other tastes
  5. 32 GI Motility
  6. What is one type of regulators of flow in the GI tract?
    • Sphincters
    • rope off (compartmentalize) different digestive areas of the GI tract
    • they ensure there’s unidirectional movement of digestive material & meter what “moves on” in the digestive process
    • they relax as food is swallowed → tighten up again as food passes
  7. Components of the Total Liquid Environment of the GI Tract
    • Saliva: secrete ~1 L/day
    • Liquid Ingestion: 2.3 L
    • Gastric Juices: 2 L
    • Bile: 1 L
    • Pancreatic juice: 2 L
    • Intestinal juice: 1 L
    • TOTAL: 9.3 L
    • the small intestine (SI) reabsorbs 8.3 L, while the large intestine (colon) reabsorbs 0.9 L
    • a total of 9.2 L is reabsorbed, meaning that only 0.1 L (100 mL) is excreted in feces
  8. Why do we need all this fluid?
    • it’s important for the digestive process
    • digestion would be SLOWED w/o the liquid environment b/c enzymes are more mobile in a fluid environment
    • w/o water, they’d get stuck in “sludge” & couldn’t work as efficiently
  9. *What are the 7 sphincters in the GI tract?
    • a. Upper Esophageal (UES): top part of the esophagus
    • b. Lower Esophageal (LES): end of the esophagus, beginning of stomach
    • c. Pyloric: end of the stomach, beginning of duodenum
    • d. Oddi: duodenum
    • e. Ileocecal: end of ilium, beginning of colon
    • f. Internal Anal
    • g. Externa Anal
  10. What is a cause of heart burn?
    • it can happen because the Lower Esophageal Sphincter (LES) doesn’t constrict fully after food has passed from the esophagus into the stomach
    • stomach acid can splash up into the esophagus, causing burning pain
  11. Pyloric Sphincter
    • unlike the esophageal sphincters that allow all swallowed material to pass through, THIS is a metering one
    • it can restrict or selectively allow small amounts of material to pass into the SI
    • allows stomach digestion to occur fully & limits SI epithelial cell exposure to the stomach’s highly acidic & destructive environment
    • (the Ileocecal Sphincter at the entrance to the colon also meters digestive contents)
  12. What is the ONLY sphincter that food does not move through, only goes by?
    • the Oddi Sphincter
    • it controls the flow of bile (from the liver) & pancreatic enzymes + fluid into the SI
    • lies in the duodenum of the SI JUST after the stomach empties into the SI
  13. Over which sphincter do you have some control?
    • you have SOME control over the External Anal Sphincter; can relax it during defecation
    • the rest of them are all controlled by the autonomic n.s.
  14. Sphincters, Muscle Type, Function
    • esophagus has 2
    • 3 more in the middle
    • anal has 2
  15. Stages of Swallowing
    1. tongue rises, closing the oropharynx

    2. soft palate rises, shutting off the nasopharynx* so food doesn’t go into/come out your nose

    3. hyoid rises & moves forward

    4. esophagus anterior wall is drawn forward by the hyoid

    5. esophageal lumen is pulled open

    • 6. epiglottis tilts backward to shut off the glottis* so food doesn’t go into the airway
  16. Gut & the Autonomic Nervous System
    • made up of the enteric, sympathetic, & parasympathetic nervous systems
    • SNS stimulation CONTRACTS GI sphincters & BVs and INHIBITS GI secretion & motor activity
    • in contrast, PSNS stimulates these digestive activities
  17. Gut Enteric Nervous System
    • GUIDES the functions of the GI tract - is the MAJOR controlling factor, even though there are SNS & PSNS innervations as well
    • can be seen along the entire GI tract from the esophagus → the colon
  18. Enteric Nervous System Functions
    • it controls movement of food along GI tract
    • regulates temperature
    • sensory regulation of enzyme secretion
    • + it senses pH & the concentrations of amino acids, fats, & carbohydrates
  19. What neurotransmitters are secreted by Enteric neurons?
    • Acetylcholine (excitatory when food is present): stimulates SM muscle contraction, ↑ intestinal secretions + release of enteric hormones, & dilates BVs
    • Norepinephrine: from extrinsic sympathetic neurons is almost always INHIBITORY & has the opposite effect of ACh
    • might see in STOMACH after a large meal slowing things down
  20. What are the 2 orientations of smooth muscle in the GI tract?
    • circular & longitudinal
    • circular muscles SQUEEZE, longitudinal muscles CONTRACT
    • intestinal layers, outermost layer → lumen
  21. What are the 2 plexuses that make up the enteric nervous system?
    • 1. Myenteric
    • 2. Submucous
    • both of these are embedded in the digestive tract wall & extend from esophagus → anus (these are the main components of the Enteric NS, control the “brain” of the GI tract)
  22. Submucous Plexus
    • is buried in the Submucosa (closer to the lumen)
    • its principal role is in sensing the environment within the lumen, regulating gastrointestinal blood flow, & controlling epithelial cell function
    • it feeds the information it senses up into the myenteric plexus
  23. Myenteric Plexus
    • located between the longitudinal & circular layers of muscle in the Tunica Muscularis
    • it exerts control primarily over digestive tract MOTILITY
  24. What 3 types of neurons can be found in the Enteric plexuses (submucosal & myenteric)?
    1. Motor: control GI motility & secretion

    2. Sensory: receive info from sensory receptors in the mucosa & muscle (includes mechanical, thermal, osmotic, & chemical stimuli)

    • 3. Interneurons: integrate info from sensory neurons & transmit it to ("programming") enteric Motor neurons
    • most of these are multipolar
  25. Where is the only place in the GI tract where there is epithelial stratification?
    • in the Esophagus
    • everywhere else in the GI tract there is a single layer of epithelial cells that are just like any other epithelium
    • there is also Striated Muscle in the 1st 3rd of the esophagus - throughout the rest of the GI tract there’s only smooth muscle
  26. Order of Relaxation/Contraction of GI Tract
    • when material moves through the GI tract, the tract in front of it RELAXES (eg. by Nitric Oxide, NO)
    • behind the material muscles CONTRACT so the stuff is propelled through/keeps moving forward
    • muscle tone relaxation (+NO) happens PRIOR to contraction (+ ACh)
    • [usually you think of ACh functioning in the PSNS to relax BVs, but in the gut you have to REVERSE your thinking & remember that the PSNS STIMULATES GI function therefore ACh → CONTRACTION]
  27. How does contraction activity vary in the stomach from the Lower Esophageal Sphincter to the Pyloric valve?
    • activity/stomach muscle contractions get MORE intense as food moves down the stomach length-wise
  28. Stomach Contraction Morphology
    • Proximal Stomach (near LES): large, lazy contractions
    • as you move down the stomach contractions become more NUMEROUS & sharp
    • tracing in SI shows a LOT of activity & mixing happening
    • stomach shows a progressive increase in the # of contractions seen as you move from its beginning to end
  29. Which leaves the stomach faster, liquids or solids?
    • LIQUIDS - they leave the stomach much faster than solids
    • eg. to get a lot of energy or electrolyte into your system it will happen more quickly if given in liquid form (takes longer to get into SI & be absorbed if solid)
    • takes 30 minutes for 1/2 of liquid to be gone, & takes 90 minutes for 1/2 of solid to leave the stomach
  30. How is movement in the large intestine DIFFERENT from that in the small intestine?
    • there are mostly MASS (large volume*) movements in the colon as opposed to the small sharp movements that occur in the SI
    • large movements happen 3-5x a day