Your Second Brain

The phrase "gut feeling" is more literal than it sounds. Your digestive tract is wrapped in its own web of nerve cells - around 100 million neurons, more than the human spinal cord. Scientists call it the enteric nervous system, your second brain.

It runs much of digestion on its own, without checking in upstairs. After a meal it quietly coordinates the muscles and juices that move food along, and it can sense when something is off down there long before you consciously notice. That steady, behind-the-scenes work is a real network reading your body the entire time.