Nadis are not nerves but rather channels for the flow of consciousness. The literal meaning of nadi is 'flow'. Just as the negative and positive forces of electricity flow through complex circuits, in the same way, prana shakti (vital force) and manas shakti (mental force) flow through every part of our body via these nadis. According to the tantras there are 72,000 or more such channels or networks through which the stimuli flow like electric current from one point to another. These 72,000 nadis cover the whole body and through them the inherent rhythms of activity in the different organs of the body are maintained. Within this network of nadis, there are ten main channels, and of these ten, three are most important for they control the flow of prana and consciousness within all the other nadis of the body. These three nadis are called ida, pingala and sushumna.
Ida nadi controls all the mental processes while pingala nadi controls all the vital processes. Ida is known as the moon, and pingala as the sun. A third nadi, sushumna, is the channel for the awakening of spiritual consciousness. Now the picture is coming clear; prana shakti - pingala; manas shakti - ida; and atma shakti - sushumna. You may consider them as pranic force, mental force and spiritual force.
As sushumna flows inside the central canal of the spinal cord, ida and pingala simultaneously flow on the outer surface of the spinal cord, still within the bony vertebral column. Ida, pingala and sushumna nadis begin in mooladhara in the pelvic floor. From there, sushumna flows directly upwards within the central canal, while ida passes to the left and pingala to the right. At swadhisthana chakra, or the sacral plexus, the three nadis come together again and ida and pingala cross over one another. Ida passes up to the right, pingala to the left, and sushumna continues to flow directly upwards in the central canal. The three nadis come together again at manipura chakra,
the solar plexus, and so on. Finally, ida, pingala and sushumna meet in the pineal gland - ajna chakra.
Ida and pingala function in the body alternately and not simultaneously. If you observe your nostrils, you will find that generally one is flowing freely and the 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 pingala 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 chitta, pingala 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 functioning of life force and consciousness can take place only if the central canal - sushumna, is connected with kundalini, the source of energy. If sushumna can be connected in the physical body, it can reactivate the brain cells and create a new physical structure.
Kundalini tantra.