A surgical instrument system has a control section operatively coupled to an instrument manipulator assembly. The control section comprises an operator control station having an operator control input device. The instrument manipulator assembly comprises a drive system and an insertion section at least a portion of which is insertable through an aperture in a patient through a location adjacent a worksite within the patients body. The insertion section includes an arm having a proximal end, a distal end and a longitudinal axis extending between the proximal and distal ends, at least one durable member having a proximal end and a distal end, the durable member being connected to the arm and arranged to extend distally of the arm. The insertion section also includes an end effector coupled adjacent the distal end of the steerable member. The drive system includes a plurality of actuator motors and linkages and is operatively coupled to both the insertion section and the control section so that the operator is able to use the input device to operate the insertion section in such a manner as at least to move the steerable member so as to provide the end effector with at least one degree of freedom of motion relative to the arm.
