72,000 Nadis or channels (distributaries) spring from Kanda, which is the point of confluence and branching (distributaries) and where Maya holds its sway. Only fourteen Nadis are important: Susumna, Ida, Pingala, GAndhara, Hastyihvika, KuhU, Sarasvati, Pusa, Sankhini, Payasvani, Vauni, Alambusa, Vishvodari,Yoshasvani. The most important of these are the Yogic Nadis: Susumna, Ida and Pingala. Swami Sivananda lists the following 14 Nadis.
Sushumna
Ida
Pingala
Gandhari
Hastajihva
Kuhu
Saraswati
Pusha
Sankhini
Payasvini
Varuni
Alambusha
Vishvodhara
Yasasvini
Nada is flow and Nadi is channel. Energy (Prana) flows in Nadis as in the electrical system. 72,000 Nadis pervade the whole body. These are not anatomical like arteries, veins, lymphatic channels or nerves. They are subtle and thus are called Yoga Nadis. What a Nadi for the Yogi is Meridian in English, Pinyin in Chinese Medicine, Keiraku in Japan, and Kyungrak in Korea. Prana of yogis and Qi of China flow in the channels or Meridians, which are interconnected. The Chinese call them Acupuncture points along the meridians, the pathways of qi, vital energy. Indian perspective: Marma is a mortal anatomical point by manipulating which death can be caused. Marma is derived from mara, marana meaning death. (You might have noticed in the TV series, Walker Texas Ranger, a practitioner pressing the Marma point and disabling the victim or the culprit without use of force.) Marma points are situated along the meridians: the Mamsa (flesh), vessels and nerves (Sira), tendons (Sanyu), Asthi (bones), and Sandhi (joints). Massage, digital pressure, acupuncture, magnets, herbals are applied to these points for curative purposes. Vigorous finger strokes at critical points can cause paralysis, impotence and other unwelcome diabolical events according to practitioners of the art. What Prana is in India is Qi in china. The meridians are positive (Yang of China and Pingala of India) and negative (Yin of China and Ida of India). Ida is left, Lunar and cool; Pingala is right, Solar and hot. Marma point is most susceptible to injury when Prana or vital energy flows through it. Ayurvedic practitioners are of the opinion that professional massage of the Marma points (107 in number) releases toxins from Marma and restores optimal health of body and mind by establishing normal energy flow. Qi flows through the subcutaneous tissue, according to the claimants. Nadis pervade the body in every which way they can and do not respect anatomical demarcations. For example: the anterior branch of the Susumna Nadi pierces the palate, passes through the brain upwards in almost a straight line and ends in Brahma Randhra, the anterior Fontanel area. Remember that Susumna Nadi is not an anatomical entity.
1) Susumna Nadi: This subtle channel goes through the spinal column. It takes its origin in Muladhara Chakra, courses through the spinal column along the Central Canal of the Spinal Cord, (the anterior branch) perforates through the palate and ends in the Brahma Randhara area of the Sahasrara Chakra. The posterior branch taking off from below the Ajna Chakra goes backwards, pierces through between the two lobes of the cerebellum, goes along the upper layers of cortex anteriorly and ends up in Brahma Randhra. What this means is that energy goes to the cerebrum and cerebellum via the Susumna Nadi's two branches. There is a diagrammatic representation of Susumna Nadi as a set of three tubes telescoped within each other: the central channel is Brahma Nadi, the middle channel is Chitra Nadi and the outer channel is Vajra Nadi. The Brahma Nadi is the most important. Rajasic Vajra Nadi or Vajrini is Solar; Sattvic pale Chitra Nadi (Chitrini) is Lunar and ambrosial; and Tamasic Brahma Nadi is the central one. Chitra means painted picture. Chitra Nadi is the dominant channel in artistic and imaginative professionals: painters, poets... and terminates in Lunar Chakra within Sahasrara Chakra. Swami Sivananda states that Chitra Nadi beginning at Brahma Dvara (the door of Brahman) in Muladhara, goes up the spinal column to Brahma Randhara and ends in cerebellum. Susumna Nadi and other Nadis excepting Ida and Pingala Nadis exhibit reciprocally alternating activity and rest. Flow in one shuts down the others. Elsewhere I spoke about the Nasal Cycle, wherein one nostril is open and the other is blocked for airflow: these are the left Ida Nadi and the Right Pingala Nadi. The practitioners say that when there is a switch in airflow from one nostril to the other in the Nasal Cycle, the airflow through both nostrils are present briefly for the duration of ten breaths, the point in time when Susumna Nadi becomes dynamic with flow of energy. (I note that many times during the day, both my nostrils are open for airflow for a long time; at other times I experience the alternating Nasal Cycle.) One source tells that other Nadis become energy-neutral, when Kundalini goes up the dynamic Susumna Nadi, which is open for energy flow at sunup and sundown, the points in time when meditation is easily advantageous. Yogis by Pranayama (breath control) can activate the Susumna Nadi any time. Ida and Pingala Nadis are described elsewhere. These Psychic Nadis convey Prana Sakti and Manas Sakti (the power of breath and mind). Kundalini lies coiled three and half times like a serpent at the base of the vertebral column, ready to spring. The three coils stand for A U M; three gunas, sattva, Rajas, and Tamas; and three states of consciousness, waking, dream sleep and deep sleep. The half coil stands for transcendence above all the triads. This energy goes through nodal points along the spine called Chakra or wheel, which is represented by lotus petals, which always point towards the goddess Kundalini where she is active. Where Kundalini sakti is active (dynamic aspect of Sakti), that chakra is hot and becomes cold when the energy leaves that chakra or plane. Once the ascent is complete, the whole body except the crown is as cold and rigid as a corpse. The nectar released by the union of Sakti and Siva pervades and sustains the whole body. The energy (sakti) goes through channels from Muladhara chakra at the base of the spine (Adhara Chakra or Support) to the Sahasrara plane at the crown by channels known as Nadis, which are subtle and not physical. Below Muladhara Chakra, there are Chakras of lower order, responsible for animal and human instinct, and intellect. Kundalini’s purpose is for the Yogi to attain Samadhi. All the senses including the sexual impulse are suppressed and sublimated into prana or energy that ascends the Susumna Nadi from Muladhara Chakra to Sahasrara chakra where goddess Kundalini and the Yogi achieve Mithuna (union) with Siva. This is not a physical union. As you go up the Chakras, you leave behind the body made of earth, water, fire, air, and ether. It is the Spirit that unites with Siva. Siva is the purest of the pure and does not allow contamination by matter. The Yogi's soul departs the body and escapes through Brahma Randhra, the anterior fontanel area, to merge with Brahman. This area is said to be 12 inches above the crown and is called vâtasântam (Dvatasantam / dvadasanta), where absorption of Yogi's consciousness into the Pure Consciousness (Universal Consciousness) of the Lord takes place. It is Turiya and Turiyatita state, 4th and 5th state of consciousness. Brahma Randhra (anterior fontanel area on the top of the head) in the skull is the entry and exit point for the soul. If you look at the top of baby's (infant) head, you will see pulsations: that is anterior fontanel and Brahma Randhra. The Sadhakas or aspirants have to follow the eight point observance, known as Ashtanga Yoga. Please read TMTM 01-09 for more details. There is one simple test whether the Shakti is actually aroused. When she is aroused intense heat is felt at that spot but when she leaves a particular centre the part so left becomes as cold and apparently lifeless as a corpse. The progress upwards may thus be externally verified by others. When the Shakti (Power) has reached the upper brain (Sahasrara) the whole body is cold and corpse-like; except the top of the skull, where some warmth is felt, this being the place where the static and kinetic aspects of Consciousness unite. Woodroffe, page 22, Introduction, Serpent Power. Those who wish to go farther, and to put into actual process this Yoga, must first satisfy themselves of the value and suitability of this Yoga and then learn directly of a Guru who has himself been through it (Siddha). His experience alone will say whether the aspirant is capable of success. It is said that of those who attempt it, one out of a thousand may have success. If the latter enters upon the path, the Guru alone can save him from attendant risks, moulding and guiding the practice as he will according to the particular capacities and needs of his disciple. Whilst, therefore, on this heading it is possible to explain some general principles, their application is dependent on the circumstances of each particular case. Woodroffe, Serpent Power page 25.
( The following is my understanding and interpretation of what Swami Chinmoy says; they are not necessarily his actual words. He says that when, for example, the Anahata heart center opens, heat rises locally accompanied by a revolving disc in the spiritual heart, which is not the fleshy heart, but located in the center and to the right of the chest. He is of the opinion that a sadhaka should open the Anahata center first before the lower centers, which are the repository of strength, power, passion, motion, sexual tension, and other animal attributes. Exercising a control over these awakened attributes, when Muladhara, Svadhisthana and Manipura centers are activated, is difficult; the raw power of these forces can lead a Sadhaka astray; they may leave him addicted to sex, drugs, and aggression, exerting power over the weak and the innocent, and living a roller coaster emotional life. Starting at the base has its disadvantages, when the Sadhaka is not physically, mentally and spiritually pure and prepared. The Sadhaka can meditate on the heart center first; pure love for self and others will grow on him; purity will envelope him; all baser qualities come to a naught; his world becomes one of joy and peace; he becomes one with the universe and what he sees, hears, smells, and touches. When he sees a flower, he becomes the flower; when he hears music, he becomes the music. At this juncture he can open the lower centers without fear of any adverse effects.) We are all in various stages of spiritual development (involution) without any particular effort, some in Muladhara, some in Svadhistana, some in Manipura and very few in Anahata and upper Chakras. Swami Satyananada Saraswati is of the opinion that though people have to find the "sensitive" Chakra that suits them best and go higher from there, eventually the aspirant must awaken the lower chakras and the corresponding brain centers also in order to awaken the whole brain. Page 123, Kundalini Tantra. Please read more on Dvadasantam at the end of this article. Note: The bones that you sit on are the Ischial tubercles which form the base; the root of the phallus forms the top of the triangle. See the triangle and the Kanda in the bottom of the diagram. The Susumna Nadi is a cluster of three channels one inside the other, a tube within a tube; of these, Brahma Nadi is the most important, through which the Goddess Kundalini and prana rise.
Susumna = Su + Sumna = Excellent + musical hymn, happiness or joy = perfect harmony.