Ida, Pingala & Sushumna

The Sat-Cakra-Narupana, one of the earliest text on nadis and chakra, explicitly refer to the three main nadis, calling them Sasi, Mihira, Susumna.

Sushumna Nadi connects the base chakra to the crown chakra. It is very important in Yoga and Tantra in general. Alternative medicine also refers to Sushumna sometimes. In Raja Yoga or Yoga of Patanjali, when the mind is quietened through Yama, Niyama, Asana and Pranayama the important state of Pratyahara begins. A person entering this state never complains of Dispersion of Mind. This is characterised by observing the movements/jerks in Sushumna, the central canal in the subtle body. The movements indicate the flow of Prana through the central canal and in the process, the sushumna makes the way for the ascent of Kundalini.

Pingala is associated with solar energy. The word pingala means "tawny" (taken from the word "Tan" symbolising the action of the Sun) in Sanskrit. Pingala has a sunlike nature and male energy. Its temperature is heating and courses from the left testicle to the right nostril. It corresponds to the river Yamuna. The Ida and Pingala nadis are often seen as referring to the two hemispheres of the brain. Pingala is the extroverted, solar nadi, and corresponds to the left hand side of the brain. Ida is the introverted, lunar nadi, and refers to the right hand side of the brain.

Ida is associated with lunar energy. The word ida means "comfort" in Sanskrit. Ida has a moonlike nature and female energy with a cooling effect. It courses from the right testicle to the left nostril and corresponds to the Ganges river. Ida nadi controls all the mental processes while pingala nadi controls all the vital processes.

Source - Wikipedia