A surgical access system including a tissue distraction assembly 40 and a tissue retraction assembly 10, both of which may be equipped with one or more electrodes 23 for use in detecting the existence of (and optionally the distance and/or direction to) neural structures before, during, and after the establishment of an operative corridor 15 to a surgical target site. The tissue retraction assembly 10 has a plurality of blades 12, 16, 18 which may be introduced while in a closed configuration, after which point they may be opened to create an operation corridor 15 to the surgical target site, including pivoting at least one blade 12, 16, 18 to expand the operative corridor 15 adjacent to the operative site.