Following your gut. Losing your appetite. A gutsy move. Though we often consider the gut as merely a digestive tool, these common expressions reflect the central role the gut plays in a much wider range of essential functions.
The entire digestive tract is lined by the enteric nervous system (ENS), a vast network of millions of neurons and glial cells—the two primary cell types also found in the central nervous system. While often called the second brain, the ENS not only generates the same neurotransmitters but actually predates the evolution of the central nervous system in the brain.
The functions of the ENS are crucial to life and extend far beyond digestion, as it regulates immunity, gut secretions, and enables complex, bi-directional communication between the gut and the brain. This is why a happy gut co-exists with a happy brain, and why digestive issues can lead to changes in mood and behavior.