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50 Cards in this Set
- Front
- Back
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What is the distal stomach responsible for?
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Mixing and propulsion
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What's the max BER?
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3/min
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Is there peristalsis in the proximal stomach?
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No
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What is the distal stomach responsible for?
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Mixing and propulsion
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What does peristalsis do in the distal stomach?
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Ripple of contracion to the pyloric sphincter
goes from weak to moderate to intense as it progresses through the distal stomach Non-neural |
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What's the max BER?
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3/min
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What is antral systole?
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Synchronous contraction of antral portion (including pyloric spincter)
->squirting back: retropulsion back into sphincter, responsible for breaking down of the food |
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Is there peristalsis in the proximal stomach?
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No
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What does peristalsis do in the distal stomach?
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Ripple of contracion to the pyloric sphincter
goes from weak to moderate to intense as it progresses through the distal stomach Non-neural |
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What is antral systole?
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Synchronous contraction of antral portion (including pyloric spincter)
->squirting back: retropulsion back into sphincter, responsible for breaking down of the food |
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Describe the pyloric sphincter.
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Anatomically well developed
Functionally insignificant (just doesn't let large particles through) Open at rest, closed by antal peristalsis (as opposed to the other sphincter) Very narrow lumen. behaves as a filter (only lets very fine particles through) |
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Are liquids and solids emptied by the same mechanisms?
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No
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What does emptying of liquids depend on?
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Depends on P, as long as pyloric sphincter is open
-Emptying is proportional to the P btw the proximal stomach and duodenum |
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Is peristalsis required to move liquids?
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No
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What role does receptive relaxation (RR) play in emptying of liquids?
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1)Normallyhave RR, .: ∆P is small
2) Vagotomy to Proximal stomach: ∆P is large .: Rapid emptying of liquids (intramural P is very low in proximal region) 3) Vagotomy to Distal stomach only: NOT much change in liquid emptying (Vagotomy= cutting vags nerve = no RR) |
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Why is it a problem if liquid empties very fast?
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Not good because the distal stomach can't take too much of anything at one time
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What is the breaking up of large masses of food due to?
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Retropulsion of chyme that goes back into the stomach when the pyloric sphincter closes
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What does the physical disruption and mixing of a meal do to the foods?
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Chyme (semi-liquid consistency)
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How is mixing achieved?
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*strong antral systole and the early closure of the pyloric sphincter
->as the wave of contraction passes over the antrum, some of the chyme is discharged into the duodenum, but most of it is squirted back into the corpus at high velocity ->This reropulsive turbulent flow results in effective mixing an physical disruption into a suspension of particles <1mm in diameter |
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Describe Gastric emptying of solids.
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1. FUNDIC (proximal stomach) RESERVOIR
2. ANTRAL (distal stomach) PUMP frequency (3/min) x stroke volume |
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What is the stroke volume?
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The amount of chyme that can be pumped out into the duodenum
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What does the stroke volume depend on?
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Fluidity of chyme: nothing larger then 1 or 2 ml will pump out
**Amplitude of contraction: governs gastric emptying, how much P it generates on the content |
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What is required to get distension?
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Stretch of muscle
Local ENS reflex Vago-vagal reflex |
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What does distension do?
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Has the factors that control antral peristalsis
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What effect does cutting the vagus nerve have on emptying solids?
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Contractions become less vigorous, makes emptying of solids much slower
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What do the sensory fibers inthe vagus do?
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Get integration and ACh release
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What happens in the stomahc/intestinal tract if the vagus is stimulated? cut?
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Stimulated: excite, increase contractility
Cut: weaken contrations, can get a problem in emptying the stomach |
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What are the prominent neural activitie on the proximal and distal stomach?
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Proximal: Mostly inhibitory-> NANC
Distal: Mostly excitatory |
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Describe the enterogastric reflex.
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-Factor that controls antral peristalsis
Distension: excessive, results in inhibition of gastric emptying pH < 3.5 Osmolarity: chyme is isotonic by the time it gets out of the duodenum chemicacomposition: FAT>>Ptn >carbs |
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What controls the enterogastric reflex?
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1) Neural: works through enteric and vago-vagal reflexes
2) Sympathetic nerves: can be inhibitory These can inhibit the excitatory enteric neuron ->End result: inhibit gastric emtying (antral peristalsis) |
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What are some of the hormones released from the duodenum endocrine cells?
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**Secretin
**CCK GIP VIP Neurotensin |
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What do these hormones do?
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Inhibit musculature in the antrum
-> End result: inhibit gastric emptying |
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Compare Gastric vs duodenal factors.
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Gastric factor: increased motility, rapid
Duodenal factors: decreased motility, slows down ->This is how it is regulated |
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Is vomiting the result of antiperistaltic waves?
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NO!
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What is vomiting?
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a reflex
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Where is the vomiting reflex organized?
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In the medullary Vomiting Center
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Which region gets contracted during vomitig?
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Distal part of stomach
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What causes vomiting?
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Increase in intaabdominal P (on relaxed gut)
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What happens if the respirator muscles in the diaphragm are paralyzed?
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It is impossible to vomit
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Afferent inputs for the vomitting center?
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Pharyng stimulus
GI or UG distension or irrtation Cardiac Ishemia Pain Biochem Disequilibrium Unequal stimulation of labyrinth Psychogenic factors |
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What are he efferent effects of the vomiting center?
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Widespread autonomic discharge + nausea (imbalance between sympathetic and parasympathetic activity)
Retching Emesis |
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What does emesis do?
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-Relaxation of upper GI tract and spasm of pyloric antrum and duodenum
-Conraction of abdominal muscles and diahragm |
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Where is the vomiting center?
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Blood brain barrier
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Where is the CTZ (chemoreceptor trigger zone)?
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Outside the blood brain barrier
Responds to circulating agents (drugs etc) |
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If you don't have a vomiting center, but have an inact CTZ, can you still vomit?
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No, need a vomiting center to vomit in response to anything
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What happens when the CTZ is activated?
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Sends a signa to the vomiting center
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Can you vomit if the CTZ is destroyed?
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Yes, but not really in response to circuling agents
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Can you vomit in response to circulating bacterial agents?
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Not really, because they don't act on the CTZ
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What are the 3 stage involvedin vomiting?
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1) Nausea: psychic experience
2) Retching: arupt, uncoordinated respiratory mocements with glottis closed 3) Emesis: actual expulsion of contents of upper GIT. Person takes deep breaths, closes glottis, contracts abdominal muscles, exerting P on gastric contents. |
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When is emesis completed?
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Reversal of thoracic P from negative to positive, as the diaphragm is displaced upwards, forcing the esophgeal contents to b expelled through the mouth
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