To make the body move, a signal travels along neurons -- nerve cells -- from the brain to the spinal cord. There, "lower motor neurons" pass the message on to the muscles. The end of every lower motor neuron releases a chemical, which is received by receptors in the muscle tissue. Once enough of the chemical has been received, the muscle is able to move.
Sometimes this process malfunctions and a person develops a neuromuscular disorder. Symptoms include muscular weakness, spasms, cramps and pain. The ability to breathe or swallow is sometimes affected. For example, some neuromuscular disorders are muscular dystrophy, spinal muscular atrophy and Lou Gehrig’s disease.Learn more about Human Anatomy