The main source of energy during muscle contraction is

During muscle contraction in a skeletal muscle fibre,$Ca^{2+}$ combines with

Sarcomere is the functional unit of contraction in a muscle fibre. Identify the portion of myofibril that constitutes a sarcomere.

$A$: Latent period is the interval between the application of an appropriate stimulus and the initiation of contraction.
$R$: Latent period is minimum in cardiac muscle fibres.

The functional unit of the contractile system for a striated muscle is:

In a contracted skeletal muscle fibre,