Technically known as the enteric nervous system, the second brain consists of sheaths of neurons embedded in the walls of the long tube of our gut, or alimentary canal, which measures about nine meters end to end from the esophagus to the anus. The second brain contains some 100 million neurons, more than in either the spinal cord or the peripheral nervous system, Gershon says.
This multitude of neurons in the enteric nervous system enables us to “feel” the inner world of our gut and its contents. Much of this neural firepower comes to bear in the elaborate daily grind of digestion. Breaking down food, absorbing nutrients, and expelling of waste requires chemical processing, mechanical mixing and rhythmic muscle contractions that move everything on down the line.
Scientific American now has a fascinating article about our “second brain” — a sheath of nerves in our gut which has the power to influence our feelings/mood, as well as outsourcing a lot of the orchestration of our bowel movements and digestion. It can affect our mood and sense of well-being, and it’s the source of the “butterflies in the stomach” phenomenon.