Relations between force and length in the relaxed state, diastole, and active state, systole, are important parameters standing at the basis of diastolic and systolic heart function. Calcium entry and removal in and out the muscle cell play a major role in muscle force. The difference between the systolic and diastolic force is developed force. Force is expressed relative to cross-sectional area of the muscle and called tension (stress would be a better term). The force-velocity relation, shows that velocity of contraction decreases when force increases. Stress relates to pressure (Chap. 9).
KeywordsCardiac muscle Calcium Force-length relation Force-velocity relation Sliding filament model Titin