Nadis are described as network of subtle channels. In the olden text, there are 72,000 Nadis in the psychic body. They are the visible current of light for the person who has developed the psychic vision. There are 14 principal Nadis but Ida, Pingla and Sushumna are the most Important. Nadis are also called as Nerves; Nadis are the subtle channels, through which Pranic forces flow. In the Ida, Pingala and Sushumna, last one is most important.
Sushmana: It is most important; it is originated form the Mooldhara chakra and end at the Sahasra chakra at the crown of the head passes through each chakra. It is a central channel and it is associated with river Sharsavti.
Pingla: Pingla Nadi Originated form the right side of the Moolsdhara chakra and passes in an opposite manner to that of Ida, terminating at the right side of the ajan chakra. It is red, masculine, hot, represents the Sun. It is associated with River Yamuna. It is active, extrovert Sun Nadi.
Ida: It is left channel, originated left side of the Mooldhara chakra in the spinal cord making criss-cross pathway and terminate at the left side of the Ajan chakra. It is passive, introvert, feminine. It is also called Moon Nadi.
Mooldhara is the meeting place of the all three nadis, the pranic current flows through all the three nadis alternatively. We can measure it by checking the flow of breath in the Nostril. When flow of air is greater in the left nostril, Ida is dominant, if the flow of air in the right nostril is much, Pingla is dominant, if the flow of air is equal in the both Nostril, Sushumna is predominant.
In case of Pingla is predominant, there is more vital energy for the physical work digestion of the food, body is extrovert, it generate more heat. If Pingla nadi flows at night, sleep will be restless and disturbed.
In case of Ida is dominant in the body, mental energy is dominant, mind is introvert. Mental work may be under taken. During the sleep, Ida nadi flows in the body. If Ida flows, digestive process may be slow, causing indigestion.
We can alter the flow (nadi) with help of Pranayam to get maximum benefits in performing our day today activity. In case, we have to do some mental work; we can direct the flow through Ida nadi to get maximum benefit. In twenty four hours, 12 hours Ida should dominate and the remaining 12 hours Pingla should dominate.
When Ida and Pingla nadis are balanced, most important nadis sushumna flows. If we want success in the field of meditation, sushumna should flow in our body. It awakens Kundalini and rise through the chakras. In case sushusma not flow in the body and we want to perform meditation (due to pingla nadi body will be restless and due to Ida mind will be over reactive), we will not get desirable results.
There are two type of system work for Ida and Pingla, one is sympathetic (Ida) and other is parasympathetic. Sympathetic is related to stimulation and acceleration of the activities concerned with the external environment and the deceleration of the organs to utilize lots of energy internally. It speeds up the heart, dilate the blood vessels, and increase the respiration rate and efficiency of the eyes, ears and their sense organs.
The parasympathetic is related to reduction of the heart beat, constrict the blood vessels and slow the respiration. Pranas flow in the Ida and pingla involuntary and unconsciously but we can control it with help yogic practices.