Yoga philosophy as well as Traditional Chinese Medicine (TCM), understand that the entire universe and every living being, plant or animal is given its ability to evolve & function by a universal source of vital energy commonly known as prana in yoga (Chi in TCM). Prana is often closely equated to electricity, as being the primal power which switches things on and gives them life action.
Prana circulates all around us, but it circulates in the body through subtle energy pathways called nadis, which are energy pathways that exist in a very similar way to the nervous system, but more refined and usually invisible to the eye because they are part of the subtle energy body (auric field). The entire physical body is imbued with a complex network of these nadi pathways which are allowing life energy to circulate.
Nadis are the pathways and Prana is the vital energy flowing through them. They are not part of the physical body but part of the subtle energy body of which there are many layers. In Yoga they call these layers Koshas and we have 5 of them; Annamaya kosha is the physical body, Pranamaya kosha is the prana energy body housing the meridian system, Manomaya kosha is the emotional mind and senses, Vijnanamaya is the intellect and higher intuitive capacities, Anandamaya is the bliss body of pure awareness and our divine grounding.
So the subtle energy body are the parts of us that we cant see, but which we can feel and that operate within us and constitute who we are. The Pranamaya Kosha of what we are mainly referring to here houses the meridian system of nadi pathways. There are many thousands of nadis in the human framework, but 72 are considered important and 10 are considered major. However they all stem from the 3 main nadis within the spine and these are by far the most important nadis of the subtle energy body. They are called Ida nadi Pingala nadi and Sushumna nadi.
Ida is the feminne channel, Pingala is the male channel and Sushumna is the central spiritual channel. Like yin and yang, Ida and Pingala contain the two primal forces of nature, mind and body in subtle form. Ida contains the mental force of consciousness and Pingala nadi contains the vital and active life force. Sushumna nadi is the most subtle channel of all, running up through the spine and around which Ida and Pingala criss cross at several points to help create the Chakra wheels of energy. These 3 nadis are considered the most important part of yoga practice and philosophy, because they are the foundation of being and human experience.
Pingala represents the male, positive polarity, solar force, physical vitality and dynamic activities. Ida represents the female, negative polarity, lunar energy, mental force and relaxation. Ida and Pingala also relate to the two hemispheres of the brain and central nervous system, with Ida governing the right side of the brain (artistic, holistic) and then criss crossing to control the left side of the body. Ida controls the function of parasympathetic nervous system which calms the mind and body. Pingala nadi governs the left side of the brain (linear, logical) and the right side of the body. It controls the sympathetic nervous system and stimulates the activities of body and mind. This knowledge is utilized in the various practices of yoga asana and pranayama for their desired effects. Surya Namaskar for example stimulates more the Pinglala Nadi and the Chandra Sequence stimulates more the feminine Ida nadi.
The subtle energy body containing the nadis and pranic flows is quite similar to the physical body in many ways, almost acting like a template of energy within and around it. The sushumna nadi which runs through the very centre of the spine, acts like the spinal cord of the subtle energy body and the crown chakra acts like the brain. The Chakras embedded into Sushumna nadi equate to the main nerve plexuses along the spine of the physical body. Many other nadis spread out from the major Chakras to the entire subtle energy body, just as the nerves spread out from the spine and nerve plexus to the entire physical body.
The subtle energy body starts in mooladhara chakra, which is based at the perineum in man or cervix for a woman. From mooladhara comes ida, pingala and sushumna nadis. Ida is the female channel and mental force and Pingala is the masculine channel and vital force. Sushumna is the central most subtle channel of all, through which the cosmic prana flows into our being. We enter life here and we leave it from here.
Mooladhara is the base chakra from which the three main vital channels emerge and flow up through the spinal cord. The pingala nadi leaves at the right side of mooladhara and ida nadi leaves at the left side, with both coiling upwards around the central sushumna to form the Chakra wheels of energy. The whole emphasis within yoga practice stems from the knowledge of these two primal forces and the need to balance them. When brought into this sacred alignment, a hidden locked door is opened and a powerful energy called kundalini is released upwards through the central Sushumna channel. The ascent of the kundalini force illuminates the entire chakra system, nervous system and various dormant areas of the brain responsible for higher thought, feeling and function.
Kundalini is a transcendental power said to rest in mooladhara chakra at the base of the spine. A disciplined lifestyle and specific yogic practices cause this special kundalini force to rise up sushumna nadi and open out each of the chakras as it passes through them. As chakras contain the innate potentials of consciousness when the kundalini force moves through and awakens them our innate capacities are released. The higher up we go through the chakra system, the higher and more refined our psychic abilities become. The ultimate goal in yoga is to cause the kundalini (Shakti) to rise up the central channel from mooladhara chakra and unite with pure consciousness (Shiva) at the crown of the head.
When Shakti unites with Shiva at the crown, it is said that the individual awareness and supreme consciousness merge and we become a divine self realised being. At this point our mind becomes fully awakened and so whilst living in the physical body we are now completely freed from its sufferings and are blessed with the ability to guide many others to the same state of inner freedom and bliss. In Yoga this is seen as the ultimate purpose to our life and the true cause of inner peace, happiness and fulfilment of all possible desires.