Which of the following is a contractile protein?

Myofilaments or myofibrils are

Given below are two statements:
$Statement-I$: Plasma creatinine is produced during catabolism of creatinine phosphate in skeletal muscle contraction.
$Statement-II$: Creatinine phosphate provides a ready source of high-energy phosphate.
In the light of the above two statements, choose the most appropriate answer from the options given below.

When there is a drop in the force of contraction after prolonged stimulation,it is known as

Explain the sliding filament theory of muscle contraction with neat sketches.

Based on their location in the human body or animals,the types of muscles are:
$I.$ Skeletal
$II.$ Visceral
$III.$ Cardiac
$IV.$ Non-visceral
The correct option is: