GtgtDr. Ketchum So next then following the cephalic phase, the gastric phase occurs. Gastric phase, the duration for it is three to four hours. This is a lot more complicated. So the stimuli include distension of the stomach. So remember, gastric phasethis phase originates because of the stimulus in the stomach, all right So distension in the stomach. Elevated pH in the stomach, okay So more basic, if you will. You’re also going to have proteins that are in the stomach that are going to help stimulate those chemoreceptors. And you’ll.
Also have amino acids, because some of the proteins will be broken down into amino acids. So we know that the receptors, then, are the stretch receptors that detect the distension, chemoreceptors are going to detect the elevated pH, the proteins and the amino acids thatamino acids that are in the lumen of the stomach. So then that’s going to generate short and longterm reflexes. Remember if it’s a long one, it involves the central nervous system. If it’s short, it directly stimulates the enteric nervous system. We’re going to send action potentials,.
Then, to the enteric nervous system, okay So here we’re going to send action potentials to the submucosal plexus. Remember, that’s in the submucosal gut wall, and we’re also going to send a signal to the myenteric plexus. Remember that thisthis is the nerve network that’s part of the muscularmuscularis externa. Now, let’s be a little more specific here. Because what the myenteric plexus is going to doit’s responsible for the mixing. It’s responsible for the contraction of the smooth muscles so that you can mix the chyme that’s in the stomach. Remember, you don’t call it food anymore when it’s in.
Human Physiology Regulation of HCl and Pepsinogen Synthesis Secretion Gastric Phase
The stomach you call it chyme. Now meanwhile then, you have the submucosal plexus, and once again, that’s going to stimulate mucus cells so that you synthesize and secrete mucus. It’s going to stimulate chief cells so you can synthesize and secrete pepsinogen. It’s going to stimulate the parietal cells so you can synthesize and secrete hydrochloric acid, and it’s going to stimulate the G cells so that you can synthesize and secrete gastrin. So again, gastrin’s being produced, this hormone, by the stomach. Now just like in the cephalic phase, gastrin can go into the bloodstream. And once it goes into the bloodstream,.
It will target those parietal cells and it will target those chief cells, and then you will also get synthesis and secretion of pepsinogen and HCl that way. So just like you did in the cephalic phase, here you have reinforcement of the parasympathetic nervous system once again. So the G cells aren’t just stimulated by the submucosal plexus they’re also stimulated by partly digested peptides. So those themselves will stimulate the G cells, and the G cells then will synthesize and secrete gastrin. What’s going to turn this system off What turns off the gastric phase One thing to think about is that the.
Chyme won’t stay forever in the stomach, right The chyme’s going to move into the duodenum. And when the chyme moves into the duodenum, the duodenum, then, is going to distend. There’s going to be some distention of the duodenum, so that can help trigger the system and shut the system off. What if you had a sympathetic response Would a sympathetic response shut the system down Hopefully you answered yes. So if you have a sympathetic response that’ll shut the system down. And then what specifically turns off gastrin So acidity in the lumen of the.