A patient support platform or mobile support cart is provided. The mobile support cart includes a transmission system that allows the patient and/or medical staff member to choose a stop, walk or roll mode. In the stop mode, the castor wheels are prevented from rolling across the floor by a braking mechanism. In the walking mode, the transmission causes a tracking wheel to engage the floor for providing tracked or guided motion to the mobile support cart. In a roll mode, the tracking wheel is raised and is disengaged from the floor, and the castor wheels are free to rotate. The platform is capable of supporting devices that may be attached or associated with a patient throughout their stay at a healthcare facility. The braking mechanism can include a cable and an associated brake arm, with the cable positioned to allow braking without inhibiting the ability of the castor wheel to swivel with respect to a castor mounting plate.