Firstly, the point where the axon endings and muscle connect is called the Neuromuscular junction (NMJ). These NMJ are very large and effective.
Secondly, in Vertebrates (I.e humans), motorneurons release acetylcholine (Ach). A neurotransmitter which causes the muscle to contract.
Thirdly, neurotransmitters are the last nerve cell to carry the signal. Passing on the signal to muscles or glands.