From Animal
Spirits to Social Engagement and Safety :
The autonomic nervous system and Polyvagal Therapy
Michael Stanborough | Director , Stanborough Educational Group and SI Australia
Abstract
This article traces the development of our understanding of the autonomic nervous system ( ANS ) and the vagus nerve in particular , from the Greeks to the modern era of Gellhorn , Selyes , Levine and Porges . It describes the complex re-appreciation of the ANS at the heart of Polyvagal Therapy .
The notion that the body is fundamentally divided into two systems , an animal ( somatic ) and organic ( autonomic ), originated with the ancient Greeks .( 1 ) In the second century AD Galen was able to follow the path of the vagus nerve from the cranium , exiting the jugular foramina , and travelling to the organs .( 1 ) The Latin word vagus means wandering or rambling , which is the type of journey the two branches of that nerve make through the thoracic and abdominal cavities . Galen also identified the sympathetic trunks as crossing the ribs and communicating with the organs via plexuses . He was able to identify most of the cranial nerves but incorrectly grouped the glossopharyngeal , vagus and accessory nerves within the sympathetic trunk , his sixth cranial nerve . Galen saw the nerves as pipes , allowing ' animal spirits ' to pass between the organs , a process he termed ' sympathy '.( 2 )
Over a millennium later the renowned Italian anatomist Vesalius improved upon Galen ’ s work , although he left unaltered the notion of the sixth nerve as being the source of the sympathetic trunk .( 3 ) As an interesting side bar , it ’ s worth noting that the cadavers the anatomists of the time had to work with were for the most part victims of capital punishment , via either decapitation or hanging , which made study of the cranial nerves connection to the body quite challenging ! It wasn ’ t until the French anatomist Jean Riolan , at work in the early 1600s , that the sympathetic trunk was said to originate from spinal nerves rather than from a branching off from the vagus .( 4 ) Other contributions of note regarding the autonomic nervous system ( ANS ) came from : Willis ( nomenclature of the cranial nerves , especially ' wandering ' vagus ); Winslow ( the first to document the grey and white rami communicantes ); du Petit ( who conducted sympathectomies to investigate the relationship of sympathetic nerves to cranial ones ); and Bichat ( who concluded that the ganglia functioned without any dependence on the cerebrospinal nervous system at all , a claim he supported with many experiments and observations ).( 5 ) However , to this point exploration of the nervous system was limited by the existing resources of technology to gross histology and embryology , which meant that , lacking access to microscopic detail , the enlarging understanding of anatomy was not matched by a corresponding increase in knowledge of physiology .
With the advent of advanced microscopes , studies of anatomy and physiology became increasingly more precise . The functions of the nervous system were no longer attributed to animal spirits and “ sympathy ” moving in the body . Still , it ’ s worth noting and appreciating the very prescient statement of Johnstone in 1795 , when he stated :
18 | vol29 | no1 | JATMS