Which is the smallest muscle in the human body?

During the mechanism of muscle contraction,$Ca^{2+}$ binds with which of the following?

Which of the following statements is correct regarding muscle contraction?

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.

Name the ion responsible for unmasking of active sites for myosin for cross-bridge activity during muscle contraction.

Sarcolemma is the covering of