9.7 Skeletal Muscle Disorders

Costameres

Clusters of structural proteins linking Z disks of sarcomeres to the sarcolemma of striated muscle cells

Dystrophin

Protein in muscle cells that links actin to proteins embedded in sarcolemma; stabilizes muscle cells during contractions

Hypocalcemia

Decreased blood calcium concentration

Hypocalcemia Tetany

Excessive muscle contractions caused when extracellular Ca²+ decreases below normal, spontaneously opening Na+ channels of nerve and muscles

Muscular Dystrophy

Genetic disorder that results from defects of muscle-membrane-stabilizing proteins such as dystrophin

Muscle Cramps

Involuntarily tetanic contractions related to heavy exercise; may be due to dehydration and electrolyte imbalances in the fluid surrounding muscle and nerve fibers

Myesthenia Gravis

Autoimmune disorder in which destruction of acetylcholine receptors of the motor end plate causes progressive loss of the ability to activate skeletal muscles