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包括肌细胞在内的人体各种细胞,细胞内的主要阳离子是K~+,细胞外的主要阳离子是Na~+。肌细胞内K~+浓度约为细胞外K~+浓度的30～40倍,而细胞外Na~+浓度则为细胞内Na~+浓度的12倍。这种细胞内外钾、钠离子浓度差异的形成主要靠细胞膜Na~+-K~+ATP酶和钠、钾离子泵对钠离子的主动转送。Na~+-K~+ATP酶是存在于细胞膜上的一种特殊蛋白质,有各种不同结构,每一种蛋白质只与某一种离子通透有关,即各种离子有各自的专用通道。正常情况下肌细胞受刺激兴奋时,膜上Na~+通道突然开放,而K~+通道突然关闭,因此膜对Na~+的通透性突然增大,膜便由K~+膜变成Na~+膜。故膜外的Na~+必然快速向膜内
Including muscle cells, including various human cells, the main cation in cells is K ~ +, the extracellular main cation is Na ~ +. Muscle cells K ~ + concentration is about 30 ~ 40 times the concentration of extracellular K ~ +, while extracellular Na ~ + concentration is intracellular Na ~ + concentration 12 times. This intracellular and extracellular potassium and sodium ion concentration differences mainly formed by the membrane Na ~ + -K ~ + ATPase and sodium, potassium ion pump active transfer of sodium ions. Na ~ + -K ~ + ATPase is a special protein existing on the cell membrane, and has various structures. Each protein is related to the penetration of only one kind of ion, that is, each ion has its own dedicated channel. Under normal conditions, when the muscle cells are stimulated to excitement, the Na ~ + channels in the membrane suddenly open while the K ~ + channels suddenly close, so the membrane permeability to Na ~ + suddenly increases and the membrane becomes K ~ + membrane Na ~ + membrane. Therefore, Na ~ + outside the membrane must be rapidly to the membrane