How does a neuron send a message from axon hillock

Explain how to lift the leg. Begin with the pre-central gyrus and end with the leg lifting away from my death grasp. The message from the brain is sent by neurons. How does a neuron send a message from axon hillock to axon terminal? And once it gets to the axon terminal, how does it pass the message on to the next neuron on the line? From the last axon to the muscle cell at the neuromuscular junction, how does the impulse result in the shortening of a myofiber. And how to get all those puny muscle cells to give the leg a good yank(summation and recruitment)? By the way, which muscles are using for this action? And since muscles act on bones at their joints, must include a discussion of bones and joints- the structure of a long bone and the structure of knee joint that moving.