Xi Chen
The heart’s ability to contract greatly depends on a mechanism termed excitation-contraction coupling (E-C coupling). In each heartbeat, the open of voltage gated L-type Ca2+ channel (LTCC) due to membrane depolarization results in the influx of a small amount of Ca2+, which in turn triggers massive Ca2+ release from sarcoplasmic reticulum (SR). The binding of cytosolic Ca2+ with troponin C of myofilaments induces shortening of myofilament, so the excitatory membrane depolarization is converted into cell contraction. After contraction, 99% of Ca2+ is either recycled back to SR through SR Ca2+-ATPase (SERCA), or extruded out of the cell through Na+-Ca2+ exchanger (NCX).
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