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首页> 外文期刊>American Journal of Physiology >Analysis of hystereses in force length and force calcium relations.
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Analysis of hystereses in force length and force calcium relations.

机译：滞后现象在力长与力钙关系中的分析。

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Analysis of the hystereses in the force-length relationship at constant Ca(2+) concentration and in the force-calcium relationship at constant sarcomere length (SL) provides insight into the mechanisms that control cross-bridge (XB) recruitment. The hystereses are related here to two mechanisms that regulate the number of strong XBs: the cooperativity, whereby the number of strong XBs determines calcium affinity, and the mechanical feedback, whereby the shortening velocity determines the duration for which the XBs are in the strong state. The study simulates the phenomena and defines the role of these feedbacks. The model that couples calcium kinetics with XB cycling was built on Simulink software (Matlab). Counterclockwise (CCW) hysteresis, wherein the force response lags behind the SL oscillations, at a constant calcium level, is obtained in the force-length plane when neglecting the mechanical feedback and accounting only for the cooperativity mechanism. Conversely, the force response precedes the SL oscillations, yielding a clockwise (CW) hysteresis when only the mechanical feedback is allowed to exist. In agreement with experimental observations, either CW or CCW hysteresis is obtained when both feedbacks coexist: CCW hystereses are obtained at low frequencies (<3 Hz), and the direction is reversed to CW at higher frequencies (>3 Hz). The cooperativity dominates at low frequencies and allows the muscle to adapt XB recruitment to slow changes in the loading conditions. The changeover frequency from CCW to CW hysteresis defines the velocity limit above which the muscle absorbs rather than generates energy. The hysteresis in the force-calcium relation is conveniently explained by the same cooperativity mechanism. We propose that a single cooperativity mechanism that depends on the number of strong XBs can explain the hystereses in the force-length as well as in the force-calcium relationships.
机译：在恒定的Ca（2+）浓度下的力-长度关系和在恒定的sarcomere长度（SL）的力-钙关系中的滞后现象的分析提供了对控制跨桥（XB）募集的机制的了解。歇斯底里在这里与调节强XB数量的两种机制有关：协同作用，其中强XB的数量决定了钙的亲和力;机械反馈，其中缩短速度决定了XB处于强态的持续时间。 。该研究模拟了这种现象，并定义了这些反馈的作用。在Simulink软件（Matlab）上建立了将钙动力学与XB循环耦合的模型。逆时针（CCW）滞后现象，其中，在忽略机械反馈并仅考虑协同机制的情况下，在力长平面中获得了恒定的钙水平的力响应滞后于SL振荡。相反，力响应在SL振荡之前，当仅允许机械反馈存在时，产生顺时针（CW）磁滞。与实验观察结果一致，当两个反馈同时存在时，将获得CW或CCW磁滞：CCW磁滞在低频（<3 Hz）下获得，并且方向在高频（> 3 Hz）时反转为CW。协同性在低频时占主导地位，并允许肌肉适应XB募集以减缓加载条件的变化。从CCW到CW磁滞的转换频率定义了速度极限，在该速度极限以上，肌肉吸收而不是产生能量。力-钙关系中的磁滞可以通过相同的合作机制方便地进行解释。我们建议，取决于强XB数量的单一合作机制可以解释力长以及力与钙之间的滞后现象。

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