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The diad is a structure in the cardiac myocyte located at the sarcomere Z-line. It is composed of a single t-tubule paired with a terminal cisterna of the sarcoplasmic reticulum. The diad plays an important role in excitation-contraction coupling by juxtaposing an inlet for the action potential near a source of Ca2+ ions. This way, the wave of depolarization can be coupled to calcium-mediated cardiac muscle contraction via the sliding filament mechanism.


  • Stanton, Bruce A.; Berne, Robert M.; Levy, Matthew N.; Koeppen, Bruce M. (2005). Physiology. St. Louis: Mosby. ISBN 0-323-03390-3.