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讨论肾上腺素能影响心脏节律要有心肌动作电位的离子基础知识,为此扼要介绍离子传导改变基础下心肌细胞电活动的结果(图1)。多数心肌细胞动作电位的上升是由于钠离子迅速内流(iNa)。iNa通道对河豚毒素特别敏感,在低跨膜电位值时失活。上升相后有一坪相,钾传导(gk)低下,保持膜去极化主要由钙离子(缓慢内流:is)传带的第二次去极化电流,也涉及兴奋收缩偶联。慢通道对钙内流抑制剂异搏停较敏感,且在比正常负得较少的跨膜电位(约A-45mv)时有用。心肌动作电位最终的复极化是由于钾流(ix)的激活和钙内流减少相结合。
Discussion Adrenergic heart rhythms affect the cardiac action potential ion basic knowledge, this brief introduction of ion conduction changes based on the results of cardiac myocyte electrical activity (Figure 1). Most cardiomyocyte action potentials are due to rapid sodium influx (iNa). iNa channels are particularly sensitive to tetrodotoxin and are inactivated at low transmembrane potential values. There is a plateau after the ascending phase, a low potassium conductance (gk), which keeps the membrane depolarised for the second depolarization current mainly carried by calcium ions (slow internal flow: is), also involved in excitation-contraction coupling. Slow channels are more sensitive to the infliximab than calcium influx inhibitors and are useful at transmembrane potentials that are less negative than normal (about A-45 mv). Ultimate repolarization of myocardial action potential is due to the combination of potassium current (ix) activation and decreased calcium influx.