What is the brain-gut connection?
Dan has written asking: I’ve heard about the stomach having a ‘second brain’, or there being a brain-gut connection. Are either of these true, and if so what is the point of a second brain?
Jonathan Reisman answered this...
Jonathan - Great question. There is an entire nervous system of the gut of the elementary canal — it's called the enteric nervous system. And in some ways it, it does operate semi-autonomously from our primary nervous system (the brain spinal cords coming from there). The nervous system of the gut, the entire nervous system helps control the gut: motility helps push food forward through peristalsis, helps impact blood flow to various parts of the tract, helps regulate also the endocrine function of the elementary canal. There's quite a lot of hormones that are secreted to impact its function and timing and things like that.There's also immune function in the gut itself since the external world, through the food that we eat presents a lot of microbes that can hurt us.
Jonathan - So there's a good, strong immune system also regulated by this entire nervous system. Our central nervous system does impact and regulate the entire nervous system mainly through the vagus nerve, which comes down from the brain stem and impacts the elementary canal function. But even if you sever that nerve, even if you completely separate the entire nervous system from the body's primary nervous system, it continues to function largely on its own. Not completely, but mostly on its own. It seems like a good, backup system to have that can function mostly on its own and keep you alive despite severing that connection.
Chris - So when people talk about gut instinct, they're not wrong,
Jonathan - They're not wrong, though that's one of the anatomical metaphors that we use throughout our language. But, it does make some sense.