Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
50 Cards in this Set
- Front
- Back
What is the distal stomach responsible for?
|
Mixing and propulsion
|
|
What's the max BER?
|
3/min
|
|
Is there peristalsis in the proximal stomach?
|
No
|
|
What is the distal stomach responsible for?
|
Mixing and propulsion
|
|
What does peristalsis do in the distal stomach?
|
Ripple of contracion to the pyloric sphincter
goes from weak to moderate to intense as it progresses through the distal stomach Non-neural |
|
What's the max BER?
|
3/min
|
|
What is antral systole?
|
Synchronous contraction of antral portion (including pyloric spincter)
->squirting back: retropulsion back into sphincter, responsible for breaking down of the food |
|
Is there peristalsis in the proximal stomach?
|
No
|
|
What does peristalsis do in the distal stomach?
|
Ripple of contracion to the pyloric sphincter
goes from weak to moderate to intense as it progresses through the distal stomach Non-neural |
|
What is antral systole?
|
Synchronous contraction of antral portion (including pyloric spincter)
->squirting back: retropulsion back into sphincter, responsible for breaking down of the food |
|
Describe the pyloric sphincter.
|
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) |
|
Are liquids and solids emptied by the same mechanisms?
|
No
|
|
What does emptying of liquids depend on?
|
Depends on P, as long as pyloric sphincter is open
-Emptying is proportional to the P btw the proximal stomach and duodenum |
|
Is peristalsis required to move liquids?
|
No
|
|
What role does receptive relaxation (RR) play in emptying of liquids?
|
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) |
|
Why is it a problem if liquid empties very fast?
|
Not good because the distal stomach can't take too much of anything at one time
|
|
What is the breaking up of large masses of food due to?
|
Retropulsion of chyme that goes back into the stomach when the pyloric sphincter closes
|
|
What does the physical disruption and mixing of a meal do to the foods?
|
Chyme (semi-liquid consistency)
|
|
How is mixing achieved?
|
*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 |
|
Describe Gastric emptying of solids.
|
1. FUNDIC (proximal stomach) RESERVOIR
2. ANTRAL (distal stomach) PUMP frequency (3/min) x stroke volume |
|
What is the stroke volume?
|
The amount of chyme that can be pumped out into the duodenum
|
|
What does the stroke volume depend on?
|
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 |
|
What is required to get distension?
|
Stretch of muscle
Local ENS reflex Vago-vagal reflex |
|
What does distension do?
|
Has the factors that control antral peristalsis
|
|
What effect does cutting the vagus nerve have on emptying solids?
|
Contractions become less vigorous, makes emptying of solids much slower
|
|
What do the sensory fibers inthe vagus do?
|
Get integration and ACh release
|
|
What happens in the stomahc/intestinal tract if the vagus is stimulated? cut?
|
Stimulated: excite, increase contractility
Cut: weaken contrations, can get a problem in emptying the stomach |
|
What are the prominent neural activitie on the proximal and distal stomach?
|
Proximal: Mostly inhibitory-> NANC
Distal: Mostly excitatory |
|
Describe the enterogastric reflex.
|
-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 |
|
What controls the enterogastric reflex?
|
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) |
|
What are some of the hormones released from the duodenum endocrine cells?
|
**Secretin
**CCK GIP VIP Neurotensin |
|
What do these hormones do?
|
Inhibit musculature in the antrum
-> End result: inhibit gastric emptying |
|
Compare Gastric vs duodenal factors.
|
Gastric factor: increased motility, rapid
Duodenal factors: decreased motility, slows down ->This is how it is regulated |
|
Is vomiting the result of antiperistaltic waves?
|
NO!
|
|
What is vomiting?
|
a reflex
|
|
Where is the vomiting reflex organized?
|
In the medullary Vomiting Center
|
|
Which region gets contracted during vomitig?
|
Distal part of stomach
|
|
What causes vomiting?
|
Increase in intaabdominal P (on relaxed gut)
|
|
What happens if the respirator muscles in the diaphragm are paralyzed?
|
It is impossible to vomit
|
|
Afferent inputs for the vomitting center?
|
Pharyng stimulus
GI or UG distension or irrtation Cardiac Ishemia Pain Biochem Disequilibrium Unequal stimulation of labyrinth Psychogenic factors |
|
What are he efferent effects of the vomiting center?
|
Widespread autonomic discharge + nausea (imbalance between sympathetic and parasympathetic activity)
Retching Emesis |
|
What does emesis do?
|
-Relaxation of upper GI tract and spasm of pyloric antrum and duodenum
-Conraction of abdominal muscles and diahragm |
|
Where is the vomiting center?
|
Blood brain barrier
|
|
Where is the CTZ (chemoreceptor trigger zone)?
|
Outside the blood brain barrier
Responds to circulating agents (drugs etc) |
|
If you don't have a vomiting center, but have an inact CTZ, can you still vomit?
|
No, need a vomiting center to vomit in response to anything
|
|
What happens when the CTZ is activated?
|
Sends a signa to the vomiting center
|
|
Can you vomit if the CTZ is destroyed?
|
Yes, but not really in response to circuling agents
|
|
Can you vomit in response to circulating bacterial agents?
|
Not really, because they don't act on the CTZ
|
|
What are the 3 stage involvedin vomiting?
|
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. |
|
When is emesis completed?
|
Reversal of thoracic P from negative to positive, as the diaphragm is displaced upwards, forcing the esophgeal contents to b expelled through the mouth
|