cardiac muscle cell contraction

Definition

Target type: biologicalprocess

The actin filament-based process in which cytoplasmic actin filaments slide past one another resulting in contraction of a cardiac muscle cell. [GOC:BHF, GOC:mtg_cardiac_conduct_nov11]

Cardiac muscle cell contraction is a complex process that involves the coordinated interaction of multiple proteins and cellular structures. It begins with an action potential, an electrical signal, that travels along the sarcolemma, the cell membrane of the muscle fiber. This action potential reaches the T-tubules, invaginations of the sarcolemma, which carry the signal to the interior of the cell. The T-tubules are closely associated with the sarcoplasmic reticulum (SR), a network of intracellular membrane-enclosed compartments that store calcium ions (Ca2+). When the action potential reaches the SR, it triggers the release of Ca2+ into the sarcoplasm, the cytoplasm of the muscle fiber. Ca2+ binds to troponin, a protein associated with the thin filament, which is composed of the protein actin. This binding causes a conformational change in troponin, exposing the myosin binding sites on actin. Myosin, the protein that makes up the thick filament, can now bind to actin and form cross-bridges. Myosin is a motor protein that uses ATP, the energy currency of the cell, to move along the actin filament. This movement pulls the thin filament towards the center of the sarcomere, the basic functional unit of a muscle fiber. As multiple myosin heads simultaneously bind to and pull on the thin filament, the sarcomere shortens, causing muscle contraction. The contraction cycle continues as long as Ca2+ remains bound to troponin. When the action potential ceases, Ca2+ is actively pumped back into the SR, reducing the concentration of Ca2+ in the sarcoplasm. This allows troponin to return to its resting state, blocking the myosin binding sites on actin. Myosin detaches from actin, and the muscle fiber relaxes. The coordinated contraction and relaxation of cardiac muscle cells is essential for the rhythmic pumping of the heart, which circulates blood throughout the body.'
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Proteins (7)

Compounds (356)