All these chakras are situated in a particular nerve, which is called Sushumna Nadi. This is the central nerve of backbone. Hence, concentration of mind has special effect on Sushumna Nadi. Such a state leads to a deeper concentration.
The Sushumna Nadi is related to another special nerve, which is situated at the bottom end of the spine. Its name is Kundalini Nadi. It is also called ‘Serpent’ or ‘Bhujangini’ because it is situated there in three and a half circles like a snake. When mind concentrates on Sushumna, it experiences a special awakening, which affects the Kundalini Nadi also and it experiences the straightening of it upwards (awakenness).
In this way the Kundalini, which remains dormant, awakens after regular practice for a long time. It uncoils itself and rises up along with Sushumna Nadi as a snake raises it hood. Its upper end goes up to brain and it is said the pranas of a yogi reach up to Sahasrara (Dashamdwara) that is brain. When the Kundalini rises, it goes up through all the chakras. This stage comes after a deep concentration on any one of the chakras.