Who Knew We Had Three Brains? The gut has its own independent nervous system, known as the enteric nervous system, that consists of about 500 million neurons. This system is embedded in the lining of the gastrointestinal tract, beginning at the esophagus and ending at the anus. Amazingly, the enteric nervous system can operate independently from the brain – it can function without it, and has been dubbed our “second brain”. It has a two way communication with the brain and central nervous system via the parasympathetic fibers of the vagus nerve and the sympathetic fibers of the prevertebral ganglia. This channel is known as the gut-brain axis, and links the emotional and cognitive centres of the brain with intestinal function, and vice-versa. The gut-brain axis is modulated by neurotransmitters, hormones, immune …