Atlas, or C1 as some of you may know it by, is the uppermost bone of your cervical spine. It is somewhat shaped like a football and is designed in such a way that it has the ability to support and cradle the cranium (skull) while simultaneously able to freely rotate the neck left and right without tension. C1 is incredibly critical to the body because it not only is the interface between the skull (which houses the brain) and the rest of the entire nervous system (via the spinal cord), but also because the vagus nerve runs on either side of it.
The vagus nerve, or cranial nerve 10, provides neural input to nearly all of the organs of the body, particularly the digestive organs. It is parasympathetic in nature, meaning it is part of our rest and digest relaxation nervous system. Therefore, when the nerve is flowing freely and thus communicating uninhibited with the organs of the digestive system, it creates a state of relative tranquility and ease within the body. This manifests as feeling relaxed, calm, etc. It also improves digestive function, which is the most crucial system of the body as all other parts of the body are first and foremost dependent upon it for nutrition and sustenance.
Thus, having your C1 regularly adjusted is extremely important to your ability to 'calm your nerves' and to also improve digestive function. Chronic emotional stress actually begins to create misalignment of C1, and C1 is known to relate to chronic tension headaches, TMJ problems, digestive issues, you name it! It is named atlas for a reason because, just like Atlas in the Greek myths, it literally holds up the world (the head). Any small imbalance of this bone can cause all sorts of compensations and pain patterns throughout the body. Sometimes a low back pain problem can be a C1 imbalance!