The major protein in the thick filament of skeletal muscle fibre is

The actin filament is shown below. Where does $Ca^{++}$ bind during muscle contraction?

Which of the following movements in the mammalian skeleton represents the leverage of the third order,where the force is applied at a point between the fulcrum and the point of resistance?

$ATP$ase of the muscle is located on:

$A$: All muscles follow the 'All or None' principle.
$R$: All muscles contract either fully or not at all depending upon the availability of a threshold stimulus.

Which of the following is a contractile protein of muscle?