The strongest muscle in the human body is the ......

$A : Ca^{2+}$ plays an important role in muscle contraction.
$R : Ca^{2+}$ combines with the troponin chain,displacing tropomyosin and allowing the myosin head to combine with actin to form an actomyosin complex.

Lack of relaxation between successive stimuli in sustained muscle contraction is known as

Which of the protein is not a part of thin myofilament?

Which of the following is the contractile protein of a muscle?

During muscle contraction,$(P)$ get reduced whereas $(Q)$ retain the length. Here $P$ and $Q$ are $-$