Complete the following sentence accurately, explaining your reason for accepting or rejecting each of the four phrases (more than one can be correct). The role of calcium in muscle contraction is:
A.
T o detach myosin heads from actin.
B.
T o spread the action potential from the plasma membrane to the contractile machinery.
C.
T o bind to troponin, cause it to move tropomyosin, and thereby expose actin filaments to myosin heads.
D.
T o maintain the structure of the myosin filament. heads.