How is the meromyosin formed?

The Krause membrane or $Z$-line is a structure in a myofibril that separates two adjacent:

The plasma membrane of the muscle fibre is called

During muscle contraction in humans,the

$A$: Application of stimuli repeatedly just at the start of relaxation of a muscle fibre shows an increase in the extent of contraction initially and results in treppe or staircase phenomenon.
$R$: It can be attributed to the summation effect of the sub-threshold stimuli being given again and again.

Myofilaments or myofibrils are