Title: Cardiac muscle - New World Encyclopedia
Headings: Cardiac muscle
Cardiac muscle
Contents
Structure
Overview
Intercalated disc
Appearance
Contraction mechanism and metabolism
Rate
Role of calcium
References
Credits

Content: Cardiac muscle exhibits cross striations formed by alternation segments of thick and thin protein filaments, which are anchored by segments called T-lines. The primary structural proteins of cardiac muscle are actin and myosin. The actin filaments are thin causing the lighter appearance of the I bands in muscle, while myosin is thicker and darker lending a darker appearance to the alternating A bands in cardiac muscle as observed by a light enhanced microscope. T-Tubules. Another histological difference between cardiac muscle and skeletal muscle is that the T-tubules in cardiac muscle are larger, broader, and run along the Z-Discs. There are fewer T-tubules in comparison with skeletal muscle. Additionally, cardiac muscle forms dyads instead of the triads formed between the T-tubules and the sarcoplasmic reticulum in skeletal muscle. Intercalated discs. Under light microscopy, intercalated discs appear as thin, typically dark-staining lines dividing adjacent cardiac muscle cells. The intercalated discs run perpendicular to the direction of muscle fibers.