In our lineage, ancestral species settled on an internal spine with a head at one end that could be pushed and pulled in the direction of intent. A primal mechanism facilitating these movements is the articulation between the first Cervical Vertebrae(Atlas) and the base of the Skull(Occiput). This articulation enables the head to angle up/down relative to the line of the spine. In our species, even though we have verticalized our spine, this articulation still facilitates us in moving our head in a “yes” nodding movement. The side to side movement, as seen in reptilian vertebrates, is achieved by bending the neck, which for us is the motion of touching the ear to the shoulder. The left/right movement, which for us, is nodding in the “No” pattern and facilitated by Cervical Vertebrae C1 and C2 (Atlas/Axis). Further discussion of this specific structural/functional dynamic:
ATLAS/AXIS AND HEARING/VESTIBULAR
An interesting note is that communicating “Yes” and “No” by nodding is universalized. These “instinctual” actions probably originated in the underlying neurophysiology where action and sharp visual focus associate with the head forward and extended, while hesitancy associates to the head back with visual and (in mammals) auditory scanning of the periphery. Yes and No are likely the first “words,” predating the emergence of more nuanced vocal communication. These “words” extend from specific motor functions in our Occiput/Atlas/Axis structure.
Discussed in this paper are the mechanical attributes of the Atlas/Occiput/Sphenoid articulation that relate to a specific function of our Cranial System – supporting the eyes. For a more general perspective of how this function relates to the holistic animal, it is recommended to also read the material in the post on Light Sensing. Here there is a discussion on the association between the function of the Atlas/Occiput/Sphenoid articulations and vision; visual sensory processing; and our species dimensional evolution:
The eyes and jaw team in the task of energy acquisition. Recognizing an object as nutritionally beneficial and then successfully devouring it are intrinsic to evolutionary fitness. There is a powerful drive, underpinning the original metamorphosis of animal neurophysiology, to optimize the efficiency of the integration of vision, visual processing, and the mechanics of the acquisition of nutrients. This topic is discussed further in this post on the mouth.
This material is written with Manual Therapists in mind, who may wish to embellish their model of Occiput/Atlas/Axis function with the perspectives presented on this website. It is this writer’s experience that understanding the functional role of the cranial structure discussed here immensely enhanced his ability to facilitate change in this cranial system, which he regularly finds restricted in some manner in his client cohort. A link to therapeutic resources related to this subject here:
NEURO-OPTOMETRY AND CONCUSSION
//Sphenoid/Occiput/Atlas as the top of the locomotive core and scaffold for vision.
SCM and Traps as the vertebrate motor system for head movement.
/PREDATOR/PREY SECTION ON VISION
The position of the Pituitary Gland “inside” the Sphenoid bone hints at its role as an interface between physical structure, chemical, and electrical activity in our bodies. This is called the Hypothalamic Pituitary Adrenal Axis. It makes sense that a point where all three of these systems converge to be assessed concurrently relative to each other would have survival benefit (Simultaneously evaluating these three systems relative to each other remotely would require some form of timing mechanism which is much more substantial evolutionary leap). The structural sensing (mechanotransduction) would be the richest as close to the middle of the core as is possible, pointing to the Pituitary gland’s position inside the Sphenoid Bone.
There is a paper discussing this interface between our structural, electrical, and chemical systems as an integral element of locomotion here:
The mechanics of the base of the skull as relates to vision originates with Vertebrate Physiology and the Line Dimension. The joint articulation (Atlas/Occiput) is a slide that moves the head on top of the spine in a “yes” nodding motion. It is also associated with the Frontal Plane and the Doing Archetype.
Overview of discussions on movements of the head:
MOVEMENTS OF THE HEAD
Overview of discussions on our head:
Overview of discussions on our locomotive core:
Overview of discussions on our core neurophysiology:
THE FOUR CORES
Overview of models presented on this site: