Protein Abnormalities in Neuromuscular Diseases—Part 1

Dr. W. King Engel (Moderator): We will begin the discussion of protein abnormalities in various neuromuscular diseases by first explaining our use of the term "neuromuscular diseases." Figure 1 is a diagram of what is called the "motor unit." The anterior-horn motor neuron (or lower motor neuron) lies in the anterior horn of the spinal cord, and the peripheral extension of that neuron goes out through the anterior root, through the peripheral nerve, to the terminal branches of that nerve cell. At the end of the terminal branches are the neuromuscular junctions, the connections between the nerve cell and the numerous muscle fibers, generally several hundred, that one neuron innervates. A motor neuron and the muscle fibers innervated by it comprise a "motor unit." Diseases that affect any part of the motor unit—that is, the anterior horn cell, peripheral nerve, neuromuscular junction, or muscle—are termed "neuromuscular diseases." In various conditions,