Skeletal Muscle Function

This chapter outlines skeletal muscle forms and functions, and reviews mechanisms of assessment. The chapter also introduces selected neuromuscular diseases that highlight the close relationship between muscle form and function. Skeletal muscle comprises approximately 50% of the body's mass. It is largely composed of long multinucleated spindle-shaped skeletal muscle cells (myofibers) that are highly specialized by virtue of a structured array of muscle-specific contractile proteins and conductile membranes containing ion channels and pumps. Muscles in the body differ in their constituent myofiber populations, and vascular and nerve supply, which affects the speed and force developed during muscle contraction as well as the neuromuscular disorders with which they are afflicted. This chapter explains in detail the concepts related to neuromuscular transmission, coupling excitation to contraction, muscular contraction, and muscular energetics. The chapter elaborates heterogeneity of skeletal muscle. Diagnostic laboratory methods for the evaluation of neuromuscular disorders are also discussed in detail. The chapter concludes with a discussion on selected neuromuscular disorders of domestic animals such as ion channelopathies, muscular dystrophy, and immume-mediated canine masticatory muscle myositis.