Like a kink in a garden hose, spinal trauma cuts off the flow of information that travels along afferent nerves, which send signals from the body to the brain, and efferent nerves .
If a physical reaction is wanted, consciously or subconsciously, the brain sends out its will by way of efferent nerves to the organs of expression, to the limbs, the viscera .
This it does by paralyzing efferent motor nerves (which carry commands from the brain) just where they branch from the spinal cord.