Once the Kundalini has been activated, the positive and negative ions start to interact with one another moving along their own bio-electrical nervous system channels within the body (the Ida and Pingala).
This causes the life energy (prana) to rise along the central nervous system (Shushumna) through constant attraction and repulsion, until they finally coalesce at the crown Charka (while intersecting at various charka points within the body (the 7 major chakra systems are simply points within the nervous system where large amounts of energy intersect and interact).