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Motor Units Did you ever think, “How do I move my muscles?” or “What are the series of events leading to muscle movement?” Well, there are very small mechanisms inside everyone that are called motor units. These motor units are responsible for the actions that you and I take for granted everyday. The voluntary and involuntary movements are all produced by motor units. A motor unit consists of a motor neuron, and all the muscle fibers it controls. The motor neuron cell body is located in the grey area of the spinal column. The individual axon will branch out to all of the muscle cells controlled by that motor neuron. The neuromuscular junction is the connection site of the axon to the muscle cell. Each muscle cell has its own neuromuscular junction. A single motor neuron can control any where from one to hundreds of muscle fibers (Baechle, 5). The movement of a muscle depends on the number of muscle fibers controlled by each motor unit. The quadriceps muscle group has little precision due to low motor neuron to muscle fiber ratio. The muscles of the eye however may have as little as one neuron for each muscle fiber and this is how we can make the precise movements of the eye (Baechle, 5). The electric current cal