Striated and voluntary muscle fibres are found in

Contractile tissues have the following features:
$(i)$ Mesodermal in origin
$(ii)$ They contain stretch receptors
$(iii)$ Rhythmic contractions are seen in them
$(iv)$ They do not fatigue during the life of the animal
Which of the above are characteristics of sphincters?

What is a sarcomere?

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

$ATP$ase of the muscle is located on:

During muscle contraction in humans,the: