Cardiac muscle cells produce more force when they have already shortened to less A than half of their resting length when they are stimulated more calcium is released into the fluid B around their...

Extracted text: Cardiac muscle cells produce more force when they have already shortened to less A than half of their resting length when they are stimulated more calcium is released into the fluid B around their actin and myosin filaments they are stimulated to contract before C their refractory period has ended more acetylcholine is released from D nearby neurons