The nervous system is divided into major parts.

• Central nervous system: brain and spinal cord
• Peripheral nervous system: nerves going to and from the cord to tissues such as skin, muscle, organ, and glands.
• Voluntary and involuntary nervous systems:
  • Voluntary: runs the muscles that your conscious mind controls.
  • Involuntary: runs systems like organs and glands.  The involuntary system subdivides into the sympathetic (excitatory, ramping up) and parasympathetic (inhibitory, chilling out) systems.
• There are sensory nerves (carry information to the brain) and motor nerves (carry information from the brain).  The sensory tells the brain what is happening in the physical environment (think pain, temperature, pressure) and the brain sends a response to act via the motor system. The motor system drives the muscles, organs, and glands.

• Nerve cells in bundles make up nerves that carry messages to and from the brain.

Both voluntary and involuntary exit the spine through openings between the vertebra. When one of the vertebra subluxate, nerve dysfunction occurs thereby creating organ, gland, and muscle dysfunction, as well as imbalance to the body and other systems.