Heart Electrical Phenomena

The rhythmic contractions of the heart which pump the life-giving blood occur in response to periodic electrical control pulse sequences. The natural pacemaker is a specialized bundle of nerve fibers called the sinoatrial node (SA node). Nerve cells are capable of producing electrical impulses called action potentials. The bundle of active cells in the SA node trigger a sequence of electrical events in the heart which controls the orderly pattern of muscle contractions that pumps the blood out of the heart.

心脏有节律地收缩，将生命之血泵出，这是对周期性电信号脉冲序列的反应。心脏的天然起搏点是一个称为窦房结（SA节点）的特殊神经纤维束。神经细胞能够产生称为动作电位的电信号。窦房结中的活跃细胞引发一系列心脏内的电信号事件，从而控制有序的肌肉收缩，将血液泵出心脏。

The electrical potentials (voltages) that are generated in the body have their origin in membrane potentials where differences in the concentrations of positive and negative ions give a localized separation of charges. This charge separation is called polarization. Changes in voltage occur when some event triggers a depolarization of a membrane, and also upon the repolarization of the membrane. The depolarization and repolarization of the SA node and the other elements of the heart's electical system produce a strong pattern of voltage change which can be measured with electrodes on the skin. Voltage measurements on the skin of the chest are called an electrocardiogram or ECG.

人体中产生的电势（电压）其起源在于膜电势，其中正负离子浓度的差异导致局部电荷分离。这种电荷分离称为极化。当某些事件引发膜的去极化，或者膜的复极化时，电压会发生变化。窦房结和其他心脏电气系统的元件的去极化和复极化会产生一种强烈的电压变化模式，可以通过皮肤上的电极测量。对胸部皮肤的电压测量称为心电图或ECG。

The heart's electrical control system must properly synchronize the pumping functions illustrated above.