The Significance of Na+ in E-C Coupling in Muscle
A great diversity of forms of multicellular organisms having come into being during animal evolution has determined the exclusively structural and functional variety of their muscles differing, particularly, in their mode of activation. In vertebrate twitch muscles a crucial step in excitation- contraction (E-C) coupling concerns the mechanisms whereby the electrical activity of the T-tubular membrane (TTM) induces the release of Ca2+ from the sarcoplasmic reticulum (SR). The investigation of this key question of the E-C coupling has resulted in two principal hypotheses about the nature of the T-SR signal transmission: (i) Ca2+ release from SR triggered by a change in tubular membrane polarization and (ii) Ca2+ release induced by specific chemical transmitter from the T-system.
KeywordsSkeletal Muscle Sarcoplasmic Reticulum Skeletal Muscle Fiber Charge Movement Contraction Coupling
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