[MUSIC] Okay, great. So, even though I told you we were going to concentrate on the sympathetics and the parasympathetics. We're going to start by looking at the third part of the autonomic nervous system, which is enteric nervous system. And, the enteric nervous system is one that's shared throughout the vertebrates. And it lines the digestive track, from the esophagus through the stomach, through the small intestine. And then, through the large inte, intestine and down to the anus. And throughout that length, there are intrinsic neurons that sit in the lining in the gastrointestinal tract. And these neurons form the enteric nervous system. And there are about 100 million. And these they, they form two different plexuses. One of the plexuses is responsible for, for pushing the contents of the digestive tract through. So peristalsis, this is pumping the contents of what we eat through the pathway from mouth to anus. The other plexuses are responsible for secreting stuff. So, making our feces either more or less watery. And and food is absorbed through this gastrointestinal tract. So, the way that this enteric nervous system works is that it's very automatic. This is the most automatic of the autonomic nervous system. If you just took this, it will push the food through. And so, we're not doing anything conscious to push the food through, from esophagus to anus. That's all taken care of by the enteric nervous system. As you may imagine, if you don't have an enteric nervous system. Then food doesn't get pushed through. And that actually happens in a disease called Hirschsprung's disease. And Hirschsprung's disease is identified at birth. So these kids come in and they have Hirschsprung's because a section of the, of the GI tract, typically down here, is aganglionic. It has no neurons. And therefore, it's just contracted. And everything can push down, but it can't push through that contraction. This has to be fixed surgically. So what they do is they take an innervated piece of the digestive tract. And they just, replace the in, uninnervated, the, aganglionic portion with that innervated portion. And then all is well. A, another name for Hirschprung's is megacolon. So megacolon. They got in this enlarged colon, because nothing's going through. The other aspect of this besides the automaticity that's very interesting. Is how this influences our mood and emotion. And, the, while the enteric nervous systems is completely able to do all of this peristalsis stuff on its own. It does interact with the central nervous system. And this is how it interacts. It, there is information going to the central nervous system, a lot. And there's some information coming from the central nervous system to the enteric nervous system. This is all coming to it through the parasympathetics and the sympathetics. You notice that I wro, I wrote two differently sized arrows. Because the information coming out of the enteric nervous system is about ten times more than the information that's going to the enteric nervous system. That information that comes from the digestive tract is telling us about whether we feel full. Whether we're, we just ate Thanksgiving meal and we, our, our abdomen is distended. Whether we feel gassy, whether we feel hungry, whether we feel good. It, it is telling us about the state of our GI tract. The information going to the to the enteric nervous system is a way by which our mood can now influence our GI functioning. And this is the way that if you get very nervous or excited, you may notice a difference in your bowel movements. If you get very if you're very calm, that's a different state. And so, there is a, there's an interaction between the way our, our digestive tract, our GI tract feels and the way we feel emotionally. Not surprisingly many psychiatric diseases are associated with certain GI issues as well. And so, this is I think it's a really great example of how the state of the body, the, the, just how we feel. How we feel somatically influences how we feel in our, in our brain. How we feel emotionally. [MUSIC]
