Which of the following interacts with skeletal muscles to produce movement?

Unstriped smooth muscles 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 the dark line lying in the middle of the $H$-zone called?

The muscular contraction in which the tension remains the same and the mechanical work is also done is called

Assertion : The phase of muscle contraction occurs when myosin binds and releases actin.
Reason : Muscle contraction is initiated by a signal sent by the peripheral nervous system via motor neuron.