The Vajrayana system states that the central channel (avadhūtī) begins at the point of the third eye, curves up to the crown of the head, and then goes straight down to the lower body. There are two side channels, the rasanā and lalanā, which start at their respective nostrils and then travel down to the lower body. The apāna vāyu governs the lower terminations of the three channels.
The lower end of the central channel ends in the rectum. The lower end of the lalanā ends in the urinary tract. The lower end of the rasanā channel emits semen.
The side channels run parallel to the center channel, except at locations such as the navel, heart, throat and crown (chakras) where the two side channels twist around the central channel. At the navel, throat and crown, there is a twofold knot caused by each side channel twisting once around the central channel. At the heart wheel there is a sixfold knot, where each side channel twists around three times. An important part of completion stage practice involves loosening and undoing these knots.
Within the chakras exist the ‘subtle drops’. The white drop exists in the crown, the red drop exists in the navel, and at the heart exists the indestructible red and white drop, which leaves the body at the time of death. In addition, each chakra has a number of ‘spokes’ or ‘petals’, which branch off into thousands of subtle channels running to every part of the body, and each contains a Sanskrit syllable.
By focusing on a specific chakra (while often holding the breath) the subtle winds enter the central channel. The chakra at which they enter is important in order to realise specific practices. For example, focusing on the subnavel area is important for the practice of tummo, or inner fire. Meditating on the heart chakra is important for realizing clear light. Meditating on the throat chakra is important for lucid dreaming and the practices of dream yoga. And meditating on the crown chakra is important for consciousness projection, either to another world, or into another body.
A result of energetic imbalance among the chakras is an almost continuous feeling of dissatisfaction. When the heart chakra is agitated, people lose touch with feelings and sensations, and that breeds the sense of dissatisfaction. That leads to looking outside for fulfillment. When people live in their heads, feelings are secondary; they are interpretations of mental images that are fed back to the individual.
When awareness is focused on memories of past experiences and mental verbalisations, the energy flow to the head chakra increases and the energy flow to the heart chakra lessens. Without nurturing feelings of the heart a subtle form of anxiety arises which results in the self reaching out for experience. When the throat chakra settles and energy is distributed evenly between the head and the heart chakras, one is able to truly contact one’s senses and touch real feelings.