Your central nervous system consists of your brain and your spinal cord. Proper body function is coordinated by your nervous system between all of the others systems, like your digestive, cardiovascular, endocrine and respiratory systems, etc. This happens through nerve impulses from your brain to your body, and from your body to your brain.  It is critical that these nerve impulses traveling to and from your brain communicate without glitches for proper function, movement and sensation. Your spinal bones house the spinal cord, while your skulls houses your brain. The primary reason we care about spinal decay and arthritis is because having a healhty spinal cord is critical for optimal health.