$A$ motor unit is also known as:

Give scientific reasons: Striated muscles get fatigued rapidly.

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.

Give scientific reasons: During flight,birds do not fatigue easily.

The $Quadriceps$ and $Gastrocnemius$ muscles are located in the:

Who propounded the "Sliding filament theory" for muscle contraction?