intrinsic regulation of strength of cardiac contraction in response to influences that do not depend on change in fiber length, i.e., the Frank-Starling curve, (e.g., the Anrep effect in which strength increases in response to increased afterload, and the Bowditch effect (treppe) in which strength increases in response to increased heart rate) and do not depend on extrinsic regulation (e.g., in which strength increases in response to sympathetic nerve stimulation or norepinephrine).