The chakras are connected to different physical organs. The energy from the chakras flows into these organs through the nadis. Nadi means flow of current. Like chakras, they are not located in the physical body. Nadis are the subtle channels through which the vital energy travels or flows. There are nearly 72,000 nadis in the body, of which 14 are important and three are the most important namely, Ida, Pingala and Sushumna.
Sushumna runs Mooladhara chakra, it goes to Ajna chakra. Originating from the left side of Mooladhara is the Ida nadi which goes through all the chakras and ends on the left side of Ajna chakra. From the right side of Mooladhara starts Pingala nadi which again goes through all the chakras and ends on the right side of Ajna chakra. Ida is considered as negative while Pingala is considered positive.
Ida and Pingala govern the opposite qualities, like Ida is mental & cold whereas Pingala is physical & hot. Every person is controlled by either Ida or Pingala at a time depending on which nadi is predominant for him at that time. This a person can make out by observing one’s own breath. Normally, human beings have more flow of air through one of the nostrils only. If there is more flow of air through left nostril, Ida nadi is predominant; if there is more flow of air through right nostril Pingala nadi is predominant.
In recent times, the word nadi is translated into a nerve. So the physical nerves correspond to the physical manifestations. Two main nadis i.e. Ida & Pingala correspond to two parts of the autonomous nervous system—sympathetic and parasympathetic nervous system. Pingala coincides with the sympathetic nervous system which when activated helps the body to face emergency by increasing the heart beat, sugar level etc. Hence, if Pingala nadi is more active in a person, he will be a restless person.
Ida nadi coincides with parasympathetic nervous system, which when activated, brings back the body to normalcy after it is activated. The person, whose Ida is active, is a calm person, but thinks too much. The flow of energy through Ida or Pingala is involuntary. Only by practice it can be brought under control. Sadhakas practise Pranayama to turn this involuntary flow of energy into voluntary one and fulfil the ultimate aim of attaining a desireless state by slowly ceasing the level of expectations.