Lack of relaxation between successive stimuli in sustained muscle contraction is known as

Short duration contractions are characteristic of:

The stored food material found in muscles is

Arrange the following steps of muscle relaxation in the correct chronological sequence:
$I.$ $Ca^{2+}$ ions are pumped back to the sarcoplasmic reticulum.
$II.$ $Z$-lines return to their original position.
$III.$ Masking of actin filaments occurs.
$IV.$ Relaxation of muscles.

Define the following terms:
$(1)$ Sarcomere
$(2)$ Acromion process

$A$ motor unit is also known as: