Systems for nerve and tissue modulation are disclosed. An example system may include an intravascular nerve modulation system including an elongated shaft having a proximal end region and a distal end region. The system may include an expandable frame having one or more electrodes positioned on or about the frame. An actuation assembly including a biasing element, a central shaft, and a piston may be configured to provide for controlled expansion of the expandable frame. The system may further include a control element for controlling the actuation assembly.