Nadis
Nadis are not nerves but rather channels for the flow of consciousness. The literal meaning of nadi is flow. Just as negative and positive forces of electricity flow through complex circuits, in the same way bija prana (vital force) and Manas sakti (mental force) flow through every part of our body via these nadis
{There are 72,000 nadis throughout the cage of the body. Susumna is the Sambhavi, the remaining nadis are unimportant.} According to the Tantras there are 72000 or more such channels or networks through which the stimuli flow like an electric current from one point to another. Human body is understood with great accuracy while our ancient seers understood the structure and the functioning of the vital body called Pranamaya Kosa These näòés cover the whole body and through them the inherent rhythms of activity in the different organs of the body are mentioned. Within this network of nadi, there are 10 main channels and of these ten, three are most important for the control of flow of prana and consciousness within all the other nadis of the body. These three nadis are called Ida, Pingla and Susumna. Ida nadi Controls all the mental process while Pingla nadi controls all the vital process. Ida is known as the moon, Pingla as the sun. A third nadi, Susumna is the channel for the awakening of the spiritual consciousness.
The sun and moon divide time into day and night. Susumna is the consumer of time .This is the conveyed secret. One can consider them as prana force, mental force and spiritual force. As Susumna flows inside the center canal of the spinal cord, Ida and Pingla simultaneously flow on the outer surface of the spinal cord, still within the bony vertebral column.
It is also said that Ida is Ganga, Pingla the river Yamuna. Between Ida and Pingla in the middle is this young widow, Kundalini. Ida Pingla and Susumna nadis begin in Mooladhara in the pelvic floor. From Mooladhara Susumna flows directly upwards within the canal, while Ida passes to the left and Pingla to the right. At Svadhisthana cakra or the sacral plexus the three nadis come together again and Ida and Pingla cross over one another. Ida passes up to the right, Pingla to the left and Susumna continues to flow directly upwards in the central canal. The three nadis come together again at Manipura cakra, the solar plexus, and so on. Finally, Ida, Pingla and Susumna meet in the ajna Cakra.
Ida and Pingla function in the body alternately and not simultaneously. If one observes his nostrils, he will find that generally one is flowing freely and other is blocked. When the left nostril is open, it is the lunar energy or Ida nadi which is flowing. When the right nostril is free, the solar energy or Pingla nadi is flowing.
Investigations have shown that when the right nostril is flowing, the left hemisphere of the brain is activated. When the left nostril is flowing, the right hemisphere is activated. This is how the nadis or energy channels control the brain and the events of life and consciousness.
Now, if these two energies – prana and citta, Pingla and Ida, life and consciousness, can be made to function simultaneously, then both hemispheres of the brain can be made to function simultaneously and to participate together in the thinking, living, intuitive and regulating processes.
In ordinary life this does not happen because the simultaneous awakening and function of life force and consciousness can take place only if the central canal Susumna, is connected with Kundalini, the source of energy. If Susumna can be connected in the physical body, it can reactivate the brain cells and create a new physical structure.