In the Western world, 2,000 years ago, Galen began describing the Central Nervous System as a complex of nerves which permitted animals spirits to travel from organ to organ.
On the other hand, the yogis have been describing the nervous system for thousands of years as the channels or nadis through the body. While experimenting with their own bodies, they learned how to regulate the systems using breath, meditation and diet.
In the West, it was only in 1921 that John Newport Langley, a fellow at The Royal Society, wrote his textbook that formalized the idea of the Central Nervous System and the Peripheral Nervous System. Further, he broke down the Peripheral Nervous Systems into the voluntary actions of the Somatic Nervous System and the involuntary actions in the Autonomic Nervous System (let’s call it the ANS).
Generally the ANS is considered to be outside of our consciousness. The ANS controls the functioning of the organs. This is good because we really don’t want to have to spend our day thinking about making our heart beat, our lungs expand or digesting our food. Usually when the ANS is described, a diagram shows the Sympathetic Nervous System (fight or flight) opposing the Parasympathetic Nervous System’s (rest and digest) activities.
However, in his paper, Langley also had a third system called the Enteric system.
You don’t remember learning about the Enteric Nervous System?
Don’t feel alone.
For some reason, the Enteric Nervous System (ENS) was lost by the medical community for about sixty years. Probably because it is the unsexy tube that starts at the mouth, ends at the anus and includes all the organs in-between. The ENS refers to the vast system of nerve cells that reside in our intestinal tract’s wall. Textbooks often do not include or barely mention the ENS. Even if you take a health class at a university today, in the Nervous System lecture, often the ENS is not mentioned.
In the 1980s biologists discovered the ENS was not only relevant but it is an INDEPENDENT nervous system, more complex than the spinal cord. That’s right, our digestive system has a life of its own. Today’s research shows that the Brain’s neurons may actually evolve from the ENS’ nerve tissues.
Have you ever gotten butterflies in your stomach or said “My gut response is….”.
This response comes from our “Second Brain” located, literally, in our gut. The ENS produces over thirty neurotransmitters including 95% of the serotonin produced in our body and the neurotransmitter ACTH which is produced in response to stress. The ENS is directly linked to the PNS (rest and digestion) and to our regular brain through the Vagus nerve. Many of our emotions, particularly if we are feeling stressed and depressed, stem from our gut. An unhealthy gut equals low serotonin which leads to depression.
Understanding that we have a second brain in our gut brings new light on why the yoga texts state that diet is a key component for a successful yoga practice.
The Yogi will obtain fulfillment through self-contemplation,
and practicing siddhasana regularly for twelve years.
– Chapter 1, Verse 40, Haṭhayoga Pradīpika
A really big thanks to Yogi H. David Coulter, PhD who wrote Anatomy of Hatha Yoga.
If you want to read more about yoga and the body, please click through to these related posts.