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Disorders of muscle 

Disorders of muscle
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date: 07 March 2021

The motor unit—the final common pathway for all voluntary muscle activity—is composed of an anterior horn cell, its peripheral axon, the axon terminal branches, the associated neuromuscular junctions, and the muscle fibres innervated. The muscle cells are multinucleate units with unique structures adapted for response to metabolic, nervous, and autocrine signals. Meanwhile, there are also different types of motor units: type 1—rich in mitochondria and specialized for oxidative metabolism of fat; type 2—larger fibres with abundant glycogen that generate energy by glycosis and are critical for short-lived muscle contraction. Knowledge of the underlying molecular cell biology, neurophysiology, and biochemical energetics of muscle provides a useful basis for understanding the symptoms, signs, and pathogenesis of clinical disorders affecting the muscles. Mutations in sarcolemmal proteins, such as dystrophin, cause diseases with widespread effects on skeletal muscle function, the heart, and survival.

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