The Brain And It's Control
Now for all of this movement to happen you need something to start it, to control it, and that's were the brain comes into play. all the muscles don't just act and move on their own, they need to be told when and how to move, and the nerve endings from the brain do just that.
At the end of every nerve connected to a muscle is an axonal ending. Inside these endings are synaptic vesicles that contain neurotransmitters. When getting ready to contract a muscle, the neurotransmitters are released into the synapse, the space between the axonal ending and receptor sight. The transmitters are then going to attach to protein sensors and they open up, which allows sodium floating around the outside to come it, and this causes action potential, AP to run down the muscle cell membrane called the Sarcolemma. In the sarcolemma are T-tubules, and these allow the AP to come into the interior of the muscles. The T-Tubule can sense the AP, and when it does it releases calcium that moves to the troponin and allows action potential to begin.