Sushrut rishi, the foremost surgeon of Ayurveda, describes the master sensitive spot on the head as Adhipati Marma, where there is a nexus of all nerves. The shikha protects this spot. Below, in the brain, occurs the Brahmarandhra, where the sushumnã (nerve) arrives from the lower part of the body. In Yog, Brahmarandhra is the highest, seventh chakra, with the thousand-petalled lotus. It is the centre of wisdom. The knotted shikhã helps boost this centre and conserve its subtle energy known as ojas.