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:
“Scholars who become politicians are usually assigned the comic role of having to be the good conscience of state policy.”
—Friedrich Nietzsche (1844–1900)
“Today, only a fool would offer herself as the singular role model for the Good Mother. Most of us know not to tempt the fates. The moment I felt sure I had everything under control would invariably be the moment right before the principal called to report that one of my sons had just driven somebody’s motorcycle through the high school gymnasium.”
—Mary Kay Blakely (20th century)