Black bands of myofibrils are known as

In the resting state of muscles, where is calcium stored?

Select the correct option regarding the components of myosin.

Muscle fatigue occurs due to the accumulation of . . . . . . .

Analogy type questions:
$(1)$ The portion between two successive $Z$-lines is the functional unit of contraction,which is called the sarcoplasmic reticulum / sarcomere.
$(2)$ The thick filaments in the $A$-band are held together in the middle of this band by a thin fibrous membrane. It is called the $Z$-line / $M$-line.

Match the following components with their respective locations and functions:
$(1)$ Synovial fluid
$(2)$ Troponin