Cardiac Muscle - Role of Calcium in Contraction

Role of Calcium in Contraction

In contrast to skeletal muscle, cardiac muscle requires extracellular calcium ions for contraction to occur. Like skeletal muscle, the initiation and upshoot of the action potential in ventricular muscle cells is derived from the entry of sodium ions across the sarcolemma in a regenerative process. However, an inward flux of extracellular calcium ions through L-type calcium channels sustains the depolarization of cardiac muscle cells for a longer duration. The reason for the calcium dependence is due to the mechanism of calcium-induced calcium release (CICR) from the sarcoplasmic reticulum that must occur under normal excitation-contraction (EC) coupling to cause contraction. Once the intracellular concentration of calcium increases, calcium ions bind to the protein troponin, which initiate extracellular fluid and intracellular stores, and skeletal muscle, which is only activated by calcium stored in the sarcoplasmic reticulum.

Read more about this topic:  Cardiac Muscle

Famous quotes containing the words role of and/or role:

    To win by strategy is no less the role of a general than to win by arms.
    Julius Caesar [Gaius Julius Caesar] (100–44 B.C.)

    A few [women] warrant our attention not because they have the answer but because they have rejected the mentality that insists there must be one answer. What makes them role models is not how much or how little they work, how many or how few hats they wear, but rather how well they understand, and accept, that for all rewards there will be commensurate sacrifice; for all gains, some loss; for any pleasure, some pain.
    Melinda M. Marshall (20th century)