Nervous system

Sudden anger rose in him. “What I’m looking for,” he barked, “is to be left in peace.” His voice trembled with a rage far bigger than her intrusion merited, the rage which shocked him whenever it coursed through his nervous system, like a flood.

Biotics manipulate mass effect fields using dozens of element zero nodules within their nervous system that react to electric stimuli from the brain. Amplifiers allow biotics to synchronize the nodules so they can form fields large and strong enough for practical use.