A presentation of equine bio-dynamics and the ins and outs of equitation is complete only with the inclusion of one more topic: human and equine nervous systems.
Both, man and the horse are mammals. Their function relies on the sensory-motor system, which prodeeds from the brain and constitutes the central nervous systems' core. Brain and central nervous system are located in skull and vertebra respectively, which provide for their protection. They are enveloped in a three-layered skin, the dura mater. Within the dura mater a liquid circulates, which nourishes and further protects them.
The mammal's nervous system consist of fibers for the transmission of sensory impressions and fibers for the transmission of motor commands. Nerve impulses flow as well between nervous systems. These are in addition to the central nervous system the autonomous nervous system, which handles organ functions, and the peripheral nervous system, which innervates body and extremities. A special function innervates the skin.
At front and end of the horse’s cantilevered backbone, and analogous at the top and bottom of the upright human spine, major peripheral nerves are gathered in bundles called plexi. These mix and redistribute, in the process creating the multitude of combined nerve functions needed to fulfill a creature's wills.
The autonomous nervous system backs up activities, which the will initiates. The autonomous nervous system itself, however, is not subject to will. It consists of motor fibers only, which proceed to the organs in the walls of major blood vessels. Two components, sympathetic and parasympathetic, share in the innervation of the cardiac, respiratory, digestive and urogenital organ activities of the body. They as well correspond to skin and glands.
The sympathetic is responsible for energy up-swing, the parasympathetic for its downturn, for detoxification and replenishment. The parasympathetic runs outside of and parallel to the vertebra and connects to the central nervous system in the poll and sacrum. The sympathetic also proceeds outside and parallel to the vertebra but connects to segments of the central nervous system, beginning with the first neck vertebra and in the horse ending with lumbar vertebra four, at the center of equine power. In the horse it proceeds in a double strand, which begins at thorax vertebra three and ends at thorax vertebra eighteen.
Considering the fact that mammals, that is rider and horse, are innervated by three different nervous systems, one may suspect that all three have something to do with riding. And so it is.
