In simpler terms the nadis are the arteries of the energetic body. The nadis are the fine subtle channels through which the energy flows to each part of our subtle body. They are often the subtle counterpart of the blood or nervous systems. From the point of view of the energy circulation through the body, all the nadis extract their energy from Ida and Pingala, which are the two functional modules that lie at the foundation of all mental, psychic and physical processes.
Nadis are the astral tubes made up of astral matter that carry psychic currents. The Sanskrit term ‘Nadi’ originates from the root ‘Nad’ which means ‘motion’. It is through these Nadis (Sukshma, subtle passages), that the vital force or Pranic current moves or flows. Since they are made up of subtle matter they cannot be seen by the naked physical eyes and you cannot make any test-tube experiments in the physical plane. Yoga Nadis are quite different from that of ordinary nerves, arteries and veins that are known to the Vaidya Shastra (Anatomy and Physiology).
The body is filled with innumerable nadis that cannot be counted. Different authors state the number of nadis in different ways, which range from 72,000 to 3,50,000. When we turn our attention to the internal structure of the body, we will be struck with a great wonder on seeing the intricacies as the architect happens to Divine Lord Himself who is assisted by skilled engineers and masons—Maya, Prakriti, Visva Karma, etc.
Nadis play a vital part in this Yoga. Kundalini when awakened will pass through Sushumna Nadi and this is possible only when the nadis are pure. Therefore, the first step in Kundalini Yoga is the observation of location, functions, nature, etc., as a detailed knowledge of the nadis and chakras will help in restoring back the purification of nadis.
The subtle lines, yoga nadis, have influence in the physical body. Even these subtle (Sukshma) prana, nadis and chakras have gross manifestation and operation in the physical body. The gross nerves and plexuses have close relationship with these subtle ones. Since the physical centres have close relationship with the astral centres, the vibrations that are produced in the physical centres by prescribed methods, have the desired effects in the astral centres.
Wherever there is an interlacing of several nerves, arteries and veins, that centre is called “Plexus”. The physical material plexuses that are known to the Vaidya Shastra are: Pampiniform, Cervical, Brachial, Coccygeal, Lumbar, Sacral, Cardiac, Esophageal, Hepatic Pharyngeal, Pulmonary, Ligual Prostatic Plexus, etc. Similarly there are plexuses or centres of vital forces in the Sukshma Nadis. They are known as ‘Padma’ (lotus) or Chakras. All the Nadis spring from the Kanda, which is in the junction where the Sushumna Nadi is connected with the Muladhara Chakra. According to few this Kanda is twelve inches above the anus. Out of the innumerable Nadis, there are fourteen important ones and they are:
Ida, Pingala and Sushumna are the most important and Sushumna is the chief, which is the highest and most sought by the Yogins. Other nadis are subordinate to this.
When we study the construction, location and function of the spinal cord and the Sushumna nadi, we can easily conclude that the Spinal Cord is called Sushumna nadi by the yogins of yore. The western anatomy deals with the gross form and functions of the spinal cord, while the yogins of ancient times dealt with all about the subtle (Sukshma) nature. Now in Kundalini Yoga, we need to have a thorough knowledge of this nadi.
Sushumna extends from the muladhara chakra (second vertebra of coccygeal region) to brahmarandhra. The Western Anatomy admits that there is a central canal in the spinal cord, known as Canalis Centralis and that the cord is made up of grey and white brain-matter. Spinal Cord is dropped or suspended in the hollow of the spinal column. In the same way, sushumna is dropped within the spinal canal and has subtle section which is of red colour like Agni (fire).
Within this sushumna there is a nadi by name Vajra which is lustrous as Surya (sun) with Rajasic qualities. Again within this Vajra Nadi, there is another nadi, called Chitra. It is of Sattvic nature and of pale colour. The qualities of Agni, Surya and Chandra (fire, sun and moon) are the three aspects of Sabda Brahman. Here within this Chitra, there is a very fine minute canal (which is known as Canalis Centralis). This canal is known as Brahmanadi, through which Kundalini, when awakened, passes from Muladhara to Sahasrara Chakra. In this centre, there exist all the six Chakras (lotuses, viz., Muladhara, Svadhishthana, Manipura, Anahata, Vishuddha and Ajna).
The lower extremity of the Chitra Nadi is called Brahmadvara, the door of Brahman, as Kundalini has to pass through this door to Brahmarandhra. This corresponds to Haridwar which is the gate of Hari of Badrinarayan in the macrocosm (physical plane). The Chitra terminates in the Cerebellum.
In a general sense the Sushumna Nadi itself (gross Spinal Cord) is called Brahma Nadi because, Brahma Nadi is within the Sushumna. Again the canal within the Chitra is also called Sushumna, because the canal is within the Sushumna. Ida and Pingala nadis are on the left and right sides of the spine.
Chitra is the highest and most beloved of the Yogins. It is like a thin thread of lotus. Brilliant with five colours, it is in the centre of Sushumna. It is the most vital part of the body. This is called the Heavenly way. It is the giver of Immortality. By contemplating on the Chakras that exist in this nadi, the Yogi destroys all sins and attains the Highest Bliss. It is the giver of Moksha.
When the breath flows through Sushumna, the mind becomes steady. This steadiness of the mind is termed “Unmani Avastha”, the highest state of Yoga. If you sit for meditation when Sushumna is operating, you will have wonderful meditation. When the nadis are full of impurities, the breath cannot pass into the middle Nadi, hence we practice Pranayama for the purification of Nadis.
Sushumna nadi, the central channel around which the two other nadi “revolve” is the royal path thro which the experience of the ultimate state of consciousness happens, that will lead to our transformation.
Each cell of our body, each organ, the brain and the mind, all the “elements” of our being are interconnected at a physical and subtle level, which allows us to think, talk, act and exist in a balanced, coherent, and synchronic manner, wherein each part acts for the benefit of the other parts. Inside our body, there are two energetic systems that control this process. They develop around Ida and Pingala nadi, and if we stimulate one element of this system, through the process of resonance, we will activate the whole system.
Sympathetic & Para-sympathetic Nerve Ganglia
On either side of spinal cord run sympathetic and para-sympathetic cords, a double chain of ganglia. Ganglia mean a collection of nerve-cells. These nerves are connected to all other vital systems of body to regulate their functioning. These constitute the Autonomic System which supplies nerves to the involuntary organs, such as heart, lungs, intestines, kidneys, liver, etc., and controls them. Vagus nerve which plays a vital part in human economy comes out of this sympathetic system. Sympathetic system stimulates or accelerates. Para-sympathetic system retards or inhibits. There are nerves to dilate or expand the arteries which carry pure oxygenated blood to nourish the tissues, organs and cells of different parts of the body. These are called Vaso-dilators. The left and the right sympathetic chains are connected by filaments. These cross from the right to the left side and vice versa, but the exact places where these crosses are not known, though several have attempted to find. M’Kendrick and Snodgrass in their Physiology of the Senses write: “Where the sensory fibres cross from one side to the other is not known ….. In some parts of the spinal cord the sensory fibres do cross from the right to left side and vice versa.”
Ida & Pingala Naadis
These nadi’s are present on either side of Sushumna Nadi, which resembles Sympathetic and Para-Sympathetic Nerves, which are present on either side of Spinal Cord. Ida starts from right testicle and Pingala from left testicle. They meet with Sushumna nadi at Muladhara Chakra and make a junction. This junction of three Nadis is known as Mukta Triveni.
Ida flows through left nostril and Pingala through right nostril against to their ‘origin of place’. Ida is also called Chandra Nadi (moon) and Pingala as Surya Nadi (sun). Ida is cooling and Pingala is heating.Ida is of pale & Sakthi Rupa. Pingala is of fiery red & Rudra Rupa.
Canalis Centralis — Brahma Nadi
Within the Chitra Nadi, there is a very fine minute canal (which is known as Canalis Centralis in Spinal Cord). This canal is known as ‘Brahmanadi’, through which Kundalini, when awakened, passes from Muladhara to Sahasrara Chakra. The lower extremity of Chitra Nadi is called ‘Brahmadvara’, through which Kundalini passes to ‘Brahmarandhra’ (Central Sulcus in Brain) which is in Sahasrara Chakra. The dormant serpent poses it’s mouth towards this Brahmadvara and goes into hybernation; waiting for awakening period.
Cauda Equina — Kanda
The spinal cord extending from brain to end of the vertebral column tapers off into a fine silken thread. Before its termination it gives off innumerable fibres, crowded into a bunch of nerves. This bunch of nerves is called as ‘Cauda equina’.
In physical body, Kanda is situated between the anus and root of reproductory organ ( where exactly the Cauda Equina exists as a bunch of nerves.) It is like shape of an egg and is covered with membranes. All the nadis of body spring from this Kanda. It is the junction where Sushumna is connected with Muladhara chakra. The four petals of Muladhara Chakra are on sides of this Kanda and the junction is called ‘Granthi-Sthana’, where the influence of Maya is very strong.
These are the STORE HOUSES OF COSMIC ENERGY. These Shatchakras are Muladhara, Swadhishtana, Manipura, Anahata, Visudda, & Ajna. All these are present at their specific regions along the length of Sushumna nadi.
Brain & Spinal Cord are connected by Medulla Oblongata, which is present in between, as a connecting link.Spinal cord opens into the brain through medulla oblongata, then from fourth ventricle it runs to third, then to fifth ventricle of the brain, which is the last stage.Thus entire Nervous System exists on the same meridian, on a single line starting from Brain to Cauda Equina.
Brahma Nadi in Sushumna Nadi is extended to brahmarandhra (Central Sulcus in Brain) Which is in Sahasrarachkra .Thus the entire Kundalini System exists on the same meridian, on a single line starting from Sahasrara Chakra to Kanda.
Like how the physical nervous system do have the accessorial organs like pluxes and network through out the physical body to carry out assigned functions, the astral system too has sub nadis to the major nadi’s, and pluxes at different parts of the body for proper supply and regulation of Pranic or Astral energies or Life Force.