The enteric nervous system, or the gastrointestinal (GI) tract, is often referred to as the “second brain.” Much like your brain, the GI tract relies on the same type of neurons and neurotransmitters to complete specific functions, as well as maintain communication with the central nervous system. Have you ever noticed that fluctuations in your emotions cause a reaction in your stomach? You may feel butterflies with love, nausea with anxiety or gut-wrenched with fear. This is because the brain has a direct effect on the GI system.