Acute pain travels into the spinal cord along the appropriate nerve root. The nerve root splits into a front division and a back division. Among other functions, the nerve root carries pain to the Central Nervous System (the spinal cord and brain). The pain signal is passed to a short tract of nerve cells (Interneurons), which in turn synapse with a nerve tract that runs to the brain . From there it is sent out to the rest of the brain, connecting with thinking and emotional centers. A Modifier Pathway from the brain modifies pain at the synapses in the back part of the spinal cord. It is partially for this reason that acute pain is decreased rapidly after tissue injury.