This is the shit that happens right after you swallow (okay not going there) . Unlike the Cephalic Phase of digestion that accounts for about 20 % of the gastric juices dumped in your stomach, the gastric phase elicits about two-thirds of the gastric secretions. And some really cool shit happens. In the end, literally. (Pun and double entendre)
When you shove food in your pie-hole it makes its way to your stomach and this starts the gastric activity by stretching the stomach signally a rise in pH. Next is a crap ton of activity leading to hydrochloric acid release culminating in a lowering of the pH and the food gets broken apart.
The Gastric juicy juice is like three chemicals man, acetylcholine, histamine, and gastrin.
Below pH of 2, stomach acid inhibits the parietal cells and G cells; this is a negative feedback loop that will wind down the gastric phase as the need for pepsin and HCl declines.
All together now, let’s stretch out our duodenum. Or we could wait until the stomach pushes the food (chyme) down into this the first segment of the small intestine. Once in the duodenum the acid and slightly digested fats cause what is called the enterogastic reflex, which is a fancy way of staying to the stomach….. hey fucker, I’ve got work to do. Don’t send anymore shit down here until I am done. Are you thinking stretch receptors? Are you thinking Leptin? Are you thinking this is the shit that happens to tell your brain to stop shoveling shit in your face for a minute…. Check out the big brain on brad, (pulp fiction)
Now the duodenum really gets to work with the enteroendocrine cells releasing secretin and cholecystokinin they smack the gallbladder and the pancreas on the booty to wake them up, whilst simultaneously suppressing gastric secretion and slams the sphincter (heahhaheheha..I said sphincter).. Anyway it slams the pyloic sphincter shut (like the circular muscle that opens and closes like a round door in sci fi movies)
This allows the duodenum to do its job and is the exact reason you feel like you could puke when you’ve eaten too much. Here the brain and stomach don’t communicate very clearly. If you eat too fast the signal to stop eating is stuck behind that slow car in the fast lane… god I hate that guy.