sun gives light to universe like self to body.

yatha,parkasayaty ekha,krsnam lokam imam ravih,
ksetram ksetri thatha krtsnam,parkasayati,bharat.--32

As all the light that illuminates the universe comes out of Sun,in the same manner all so souls are sourced from the super- soul.
As only one sun is giving light and heat to the universe,likewise our self which we can not see due to subtle gives energy to body,mind, intellect to do functions.by the force of self our body is doing its actions.