Depolarization of muscle refers to the process by which the cell membrane of a muscle cell undergoes a change in electrical potential, moving from a resting state to an excited state. This change is a critical part of the excitation-contraction coupling mechanism that leads to muscle contraction. In the context of skeletal muscle cells, depolarization is initiated by an action potential that travels down the muscle fiber. This action potential causes the opening of voltage-gated calcium channels in the sarcoplasmic reticulum, which then releases calcium ions into the muscle cell's cytoplasm. The increased concentration of calcium ions in the cytoplasm is what facilitates the interaction between actin and myosin filaments, leading to muscle contraction. Here's the translation of the above explanation into Chinese: 肌肉的去极化是指肌细胞膜在电位上发生改变的过程，从静息状态变为兴奋状态。这一变化是导致肌肉收缩的兴奋-收缩耦合机制的关键部分。在骨骼肌细胞的背景下，去极化是由沿着肌纤维传播的动作电位引发的。这个动作电位导致肌质网中的电压门控钙通道打开，然后钙离子被释放到肌细胞的细胞质中。细胞质中钙离子浓度的增加促进了肌动蛋白和肌球蛋白之间的相互作用，从而导致肌肉收缩。 read more >>

An action potential in the skeletal muscle cell is what triggers muscle cell contraction. We have seen that calcium ions regulate whether or not contraction can occur. Thus, what is needed is a way to link muscle excitation (the depolarization of the action potential) to Ca++ release from the sarcoplasmic reticulum.read more >>