In a resting state,the central part of the thick filaments not overlapped by thin filaments is called the .....

Sarcoplasmic reticulum is related with

Name the ion responsible for unmasking of active sites for myosin for cross-bridge activity during muscle contraction.

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

The covering around a bone is called:

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.