Chakra means a wheel–that which moves–which rotates. As the meeting point of the pranic energies of the human body and the energies of the psychic world that flow in from outside, it is called a chakra and these chakras are almost like whirlpools.
The energies are always moving; they never stop i.e. when the Kundalini touches its centres. Otherwise, they are usually asleep.
The Hathayoga Pradeepika and the Satchakra Nirupana–the two authoritative textbooks on the Kundalini and the chakras–say that basically there are three nadis–the Ida, the Pingala and the Sushumna.
Nadis are the channels through which life energy or the Prana operates. The Ida is on the left side of the spine, the Pingala is on the right side of the spine and the Sushumna is, of course, in the middle of the spine.
All the three nadis originate from the Mooladhara chakra or the root foundation centre that is at the bottom of the spine. While the Sushumna nadi goes straight up and joins the Sahasrara chakra on the top or crown of the head, the other two nadis run on either side of the Sushumna, crossing each other at the centre of the eyebrows which is called the Brumadhya or the Agya chakra and then proceeds to join the Sahasrara chakra.
“In the raising or awakening of the Kundalini, emotion or feeling plays as much part as the technique of Pranayama and the chanting of the mantras.”
So, the yogis say that the joining or the crossing together, the Sangam of the Varuna and the Asi rivers, which are represented by the Ida and Pingala nadis at the Brumadhya (also called the Agya chakra, the centre between the eyebrows), is what is known as the holy city of Varanasi–the meeting place of the Varuna and the Asi rivers.
According to the tantras, Shiva, the Supreme Being resides in the Sahasrara chakra, with his legs let down and touching the Brumadhya chakra or the centre between the eyebrows.
Now, the point at which the Sushumna enters the Sahasrara chakra is known, in the tantras and in the yogic scriptures, as the ‘Bramharandra‘–the hole or the gateway to Brahman, the Supreme Being.
And, it is interesting to note that the Bramharandra, if you compare with present-day anatomy charts, sort of coincides with what is known as the centre of the limbic system–where the pituitary gland, the amygdala, the thalamus and so on, exists in the brain.
The limbic system is that which takes care of our feelings. If the limbic system doesn’t work, we would have no feelings. Therefore, in the raising or awakening of the Kundalini, emotion or feeling plays as much part as the technique of Pranayama and the chanting of the mantras.
According to the tantrics, the practitioners of tantra, any feeling that is deep can in some way awaken the Kundalini.