The immediate regeneration of $ATP$ used up during muscle contraction is facilitated by

$A-$ Actin filaments occur in two forms: the monomeric $G$-actin and the polymeric $F$-actin.
$R-$ Tropomyosin is a rod-shaped fibrous protein. Tropomyosin forms two helical strands,which are wrapped around the $F$-actin filaments.

Assertion : The phase of muscle contraction occurs when myosin binds and releases actin.
Reason : Muscle contraction is initiated by a signal sent by the peripheral nervous system via motor neuron.

Which part of a muscle cell is the storehouse of calcium ions?

Which of the following statements are false regarding the muscle structure?
$I.$ In the centre of each $I$-band is an elastic fibre ($Z$-line) which bisects it.
$II.$ Thin filaments are firmly attached to the $Z$-line.
$III.$ $M$-line is a fibrous membrane in the middle of $A$-band.
$IV.$ $A$ sarcomere comprises one full $A$-band and two half $I$-bands.

Identify the correct labels for the parts of the myosin monomer shown in the diagram.