The enteric nervous system (ENS), sometimes referred to as the “second brain,” is embedded in the lining of the gastrointestinal system. It is the largest component of the autonomic nervous system, which also controls other involuntary functions such as heart rate, blood pressure, and breathing rate.
Through its vast web of hundreds of millions of neurones, the ENS constantly monitors the health of the digestive tract from the esophagus to the anus, communicating with the central nervous system (CNS) to maintain balance throughout.
When we talk about a gut feeling or “butterflies in the stomach,” we are essentially referring to the ENS. There is bidirectional information flow between the ENS and CNS. While the ENS normally communicates with the CNS via the parasympathetic and sympathetic nervous systems, it is composed of sensory neurones, motor neurones, and interneurons — making it capable of carrying reflexes and acting as an integrating center even without CNS input (Rao & Gershon, 2016).
The ENS has essential functions, including controlling gut motor activity (the tone of the gut and the velocity and intensity of its muscular contractions), local blood flow, mucosal transport, and secretions, as well as modulating immune and endocrine functions.
The ENS uses more than 30 neurotransmitters, most of which are identical to those found in the CNS, such as acetylcholine, dopamine, and serotonin. In fact, more than 90% of the body’s serotonin is in the gut, along with about 50% of the body’s dopamine — both central to mood and motivation.
The human gastrointestinal tract also harbours a complex, dynamic population of microorganisms known as the gut microbiota. The genetic content of the microbial communities in our gut outnumbers the human genetic content of our whole body by approximately one hundredfold (Ley, Peterson, & Gordon, 2006). A review by Carabotti and colleagues (2015) concluded that strong evidence suggests gut microbiota plays a key role in bidirectional interactions between the gut and nervous system, influencing stress responses, anxiety, and even memory.
👉 Why this matters for yoga teachers
As yoga teachers, we regularly see students arrive in class carrying stress, nerves, or fatigue. Understanding the gut–brain connection helps us recognise why these experiences often show up not just in the mind but also in the belly.
• Butterflies and anxiety: Students who feel anxious before class may describe a fluttering or tightness in the stomach. Knowing this comes from the ENS normalises their experience and reduces shame.
• Mood and digestion: Changes in gut microbiota can affect mood and cognitive clarity. While it’s not our role to diagnose, awareness of this connection encourages compassion and helps us hold space without dismissing someone’s struggles as “just mental.”
• Antibiotics and probiotics: Research shows antibiotics can disrupt gut bacteria and are linked to higher risks of depression and anxiety (Lurie et al., 2015). Probiotics may help alleviate depressive symptoms, though more research is needed (Wallace & Milev, 2017). This underscores how profoundly the gut shapes the nervous system — and why holistic approaches, including stress management practices like yoga, may play a supportive role.
👉 Teaching takeaways
• Normalize sensations: remind students that gut feelings are a real physiological process, not “all in their head.”
• Use stress-relieving practices: slower pranayama, mindful pacing, and relaxation can ease gut–brain feedback loops.
• Avoid overpromising: yoga supports balance but does not replace medical care for digestive or mental health conditions.
• Invite awareness: encourage students to notice how their belly responds to stress, food, or relaxation during practice.
👉 Teaching prompt
Next time you guide pranayama or relaxation, invite students to bring gentle awareness to sensations in the belly. Ask: “What do you notice here? Does the sensation shift as you soften your breath?”
This simple inquiry turns science into embodied experience.
References:
Carabotti, M., Scirocco, A., Maselli, M., & Severi, C. (2015). The Gut–Brain Axis: Interactions Between Enteric Microbiota, Central and Enteric Nervous Systems. Annals of Gastroenterology, 28(2), 203–209.
Ley, R., Peterson, D., & Gordon, J. (2006). Ecological and Evolutionary Forces Shaping Microbial Diversity in the Human Intestine. Cell, 124, 837–848.
Lurie, I., Yang, Y., Haynes, K., Mamtani, R., & Boursi, B. (2015). Antibiotic Exposure and the Risk for Depression, Anxiety, or Psychosis: A Nested Case-Control Study. Journal of Clinical Psychiatry, 76(11), 1522–1528.
Rao, M., & Gershon, M. (2016). The Bowel and Beyond: The Enteric Nervous System in Neurological Disorders. Nature Reviews Gastroenterology & Hepatology, 13, 517–528.
Wallace, C., & Milev, R. (2017). The effects of probiotics on depressive symptoms in humans: a systematic review. Annals of General Psychiatry, 16(14).