The backward bending of the shank is worked out by

Which type of muscles are responsible for the movement of the pinna in humans?

In a $A$ state,the edge of thin filaments on either side of thick filaments $B$ overlap the free ends of $C$ filaments leaving the central part of thick filaments. This central part of thick filament,not overlapped by thin filaments is called $D$ zone.
Choose the correct options to fill the gaps $A, B, C$ and $D$,so as to complete the given $NCERT$ statement.

Define the sliding filament theory of muscle contraction.

During muscular contraction,which of the following events occur?
$(a)$ $'H'$ zone disappears
$(b)$ $'A'$ band widens
$(c)$ $'I'$ band reduces in width
$(d)$ Myosin hydrolyzes $ATP$,releasing the $ADP$ and $\Pi$
$(e)$ $Z$-lines attached to actins are pulled inwards
Choose the correct answer from the options given below.

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