心脏传导系统由以下部分组成- The cardiac conduction system consists ofthe following components: 窦房结或SA节点 – The sinoatrial node, or SA node, 位于靠近上腔静脉入口 located in the right atrium near the entrance of the 与右心房的交界处 superior vena cava. 这是心脏的自然起搏点 This is the natural pacemaker of the heart. 它引导心脏搏动 并确定心率 It initiates all heartbeat and determinesheart rate. 电冲动从窦房结传遍了 Electrical impulses from the SA node spread 整个心房 throughout both atria and stimulate them to 并刺激它们收缩 contract. 房室结或称AV结 – The atrioventricular node, or AV node, 位于右心房的另一侧 located on the other side of the right atrium, near 在三尖瓣的附近 the AV valve. 房室结承担电冲动的作用 从心房传到心室的唯一通道 The AV node serves as electrical gateway tothe ventricles. 它能延迟电脉冲传导到心室 It delays the passage of electrical impulsesto the ventricles. 这种延迟是为了确保 This delay is to ensure 心房已经泵出所有的血液进入收缩前的心室 that the atria have ejected all the blood into the ventricles 房室结从窦房结 before the ventricles contract. 接收信号 – The AV node receives signals 并将它们传递到房室束 from the SA node and passes them onto the atrioventricular 也就是希氏束 bundle – AV bundle or bundle of His. 希氏束被分成左 – This bundle is then divided 右束支朝心尖传递冲动 into right and left bundle branches which conduct the impulses 然后这些冲动被传递到浦肯野 toward the apex of the heart. （PUR-KIN-JEE）纤维 The signals are then passed onto Purkinje fibers, 再向上传动 turning upward and spreading throughout 并使全部心室肌几乎同时被激动 the ventricular myocardium. 心脏的电活动可以记录成心电图 Electrical activities of the heart can be recorded 简称EKG或ECG in the form of electrocardiogram, 心电图（ECG或EKG）复合 ECG or EKG. 了节点和心肌的细胞产生 An ECG is a composite recording 的所有动作电位 of all the action potentials produced by the nodes and 心电图的各 the cells of the myocardium. 波形或段 Each wave or segment 对应于心脏电周期的 of the ECG corresponds to a certain event of the cardiac electrical 一个特定的事件 cycle. 当心房充盈 When the atria are full of blood, 窦房结发出冲动 电信号传遍了整个心房 the SA node fires, electrical signals spread throughout 并促使他们去极化 the atria and cause them to depolarize. 这在心电图上的用P波表示 This is represented by the P wave on the ECG. P波开始后约100毫秒 Atrial contraction, or atrial systole starts about 100 ms 心房收缩 after the P wave begins. PQ段表示信号从窦房结传到 The P-Q segment represents the time the signals travel 房室结的时间 from the SA node to the AV node. QRS波群标志房室结 The QRS complex marks the firing 发出冲动 代表心室去极化的全过程 of the AV node and represents ventricular depolarization: Q波对应于室间隔的去极化 – Q wave corresponds to depolarization ofthe interventricular septum. R波对应于心室肌的去极化 – R wave is produced by depolarization of the main mass of the ventricles. S波对应于心室除极的最后一个阶段 – S wave represents the last phase of ventricular depolarization 心室基底部 at the base of the heart. 心房复极也在此期间发生 – Atrial repolarization also occurs 但信号被QRS波群遮蔽 during this time but the signal is obscured by the ST段反映了心肌动作电位 large QRS complex. 的平台期 表示心室收缩 The S-T segment reflects the plateau in themyocardial action potential. 和泵血 This is when the ventricles contract and pumpblood. T波表示心室舒张 或者心室复极前的心肌舒张 The T wave represents ventricular repolarizationimmediately before ventricular relaxation, 每一次心跳进行 or ventricular diastole. 一个循环 The cycle repeats itself with every heartbeat.
