Which neurotransmitter is responible for contraction of muscle ?

Which neurotransmitter causes depolarization of muscle fibre? What is the role of calcium in muscle contraction ? Why is there need of a refractory period?

Assertion Arival of an impulse at the axon terminal stimulates the release of neurotransmitters in synaptic cleft. Reason These neurotransmitters are responible for the opening of ion channels.

Which is true for muscle contraction :-

Which mineral ions are important for muscle contraction?

Name the proteins which regulates the contraction of muscles .

Which element is essential for muscle contraction ?