Electron microscopic studies of the sarcomeres have revealed that during muscle contraction:

Who propounded the "Sliding filament theory" for muscle contraction?

$A$: Muscle tetanus is the phenomenon of sustained contraction of a muscle due to a succession of nerve impulses/stimuli being received by it.
$R$: Many of our daily activities are due to tetanic contraction of muscles,such as holding a book.

Short duration contractions are characteristic of:

Which of the following statements are correct regarding skeletal muscle?
$A$. Muscle bundles are held together by a collagenous connective tissue layer called fascicle.
$B$. Sarcoplasmic reticulum of muscle fibre is a storehouse of calcium ions.
$C$. Striated appearance of skeletal muscle fibre is due to the distribution pattern of actin and myosin proteins.
$D$. $M$ line is considered as the functional unit of contraction called sarcomere.
Choose the most appropriate answer from the options given below:

The protein which maintains the muscular storage of oxygen is