That sushhumnA of Yoga-shAstra starts from the mUlAdhAra at the base of the spine and goes straight up to the head.
The nADi that we saw and which is spoken of in the Upanishads and Brahma-sUtra, starts from the heart.
The process of the ascent of prANa-shakti on the sushhumnA that starts from the mUlAdhAra, is a matter that pertains to the yogis who perform SAdhanA for that purpose.
They hold on to the *lokAdhAra-shakti* and through that become one with shivaM in the head. That is a particular yoga matter.
Our Vedanta which is based on Upanishads does not touch upon those things. It will not go in a roundabout way dealing with breath, shakti, etc.
Vedanta shows the way only to experience the goal by a proper intellectual enquiry, keeping a straight aim on the target, namely the Real ‘I’ which is what subsists after the discarding of the little ‘I’.