Do Cardiac muscle fibers need outside nervous stimulation in order to contract?

No, cardiac muscle fibers do not require outside nervous stimulation to contract. They have an inherent ability to generate action potentials due to specialized pacemaker cells, primarily located in the sinoatrial (SA) node. This intrinsic property allows the heart to beat rhythmically and autonomously, although the autonomic nervous system can modulate the heart rate and contraction strength.