Unstriped muscles are found in

Involuntary muscles are

Which of the following statements is true with reference to the structure of a muscle fibre?

Which characteristic is $NOT$ associated with white muscle fibers?

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.

What happens when a sub-threshold stimulus is applied to a muscle?