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The cardiac conduction system consists of the following components:
心臟傳導系統是由 以下組成：
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- The sinoatrial node, or SA node, located in the right atrium near the entrance of the
- 竇房結或SA結點，位於右心房
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superior vena cava.
接近上腔靜脈的入口。這是自然天生的心臟激搏器。它促發心跳
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This is the natural pacemaker of the heart.
並決定心臟率。從竇房結釋放的電脈衝 傳遍兩個心房，
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It initiates all heartbeat and determines heart rate.
並刺激它們收縮。 - 房室結或AV結點，位於
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Electrical impulses from the SA node spread throughout both atria and stimulate them to
在右心房的另一邊，靠近 在AV瓣膜。 AV結點作為
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contract.
一個電通道通往心室。它延遲電脈衝到心室的傳輸。
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- The atrioventricular node, or AV node, located on the other side of the right atrium, near
這種延遲是為了確保在心室收縮前，
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the AV valve.
心房已將所有的血液擠入心室。 - AV結點接收了SA結點的訊號，
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The AV node serves as electrical gateway to the ventricles.
並將它們傳遞到房室束（atrioventricular bundle） - AV束（AV bundle）或希氏束（bundle of His）。
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It delays the passage of electrical impulses to the ventricles.
- 這個房室束接著分為左右 束網，將電脈衝
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This delay is to ensure that the atria have ejected all the blood into the ventricles
傳向心臟的頂部。此訊號接著又被 傳遞到浦金氏纖維（Purkinje fibers），
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before the ventricles contract.
並方向改由下往上，擴散到整個心室的 心肌。
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- The AV node receives signals from the SA node and passes them onto the atrioventricular
心臟的電活動可以心電圖的形式紀錄，
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bundle - AV bundle or bundle of His.
ECG或稱EKG。心電圖複合式記錄 由結點和心肌細胞產生的
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- This bundle is then divided into right and left bundle branches which conduct the impulses
所有動作電位。心電圖的每個波 或波段對應於
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toward the apex of the heart.
心電的某個事件週期。
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The signals are then passed onto Purkinje fibers, turning upward and spreading throughout
當心房充滿血液，竇房結啟動，電訊號傳遍
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the ventricular myocardium.
心房並促使它們去極化。這個 階段由心電圖的 P波呈現。
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Electrical activities of the heart can be recorded in the form of electrocardiogram,
心房收縮始於P波開始的100毫秒的之後。
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ECG or EKG.
PQ段表示訊號從SA結點傳到AV結點的時間。
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An ECG is a composite recording of all the action potentials produced by the nodes and
QRS波群表示AV結點的啟動 和心室的去極化：
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the cells of the myocardium.
- Q波對應室間隔（interventricular septum）的去極化。
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Each wave or segment of the ECG corresponds to a certain event of the cardiac electrical
- R波是由心室大部份心肌的去極化所形成。
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cycle.
- S波代表心室去極化的最後階段。
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When the atria are full of blood, the SA node fires, electrical signals spread throughout
心房的再極化在同時間發生，但它的訊號被
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the atria and cause them to depolarize.
更強大QRS波群蓋過。 ST段反映了心肌動作電位
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This is represented by the P wave on the ECG.
的穩定階段。這時心室收縮並打出血液。
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Atrial contraction , or atrial systole starts about 100 ms after the P wave begins.
T波表示心室心肌放鬆或稱心室舒張前
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The P-Q segment represents the time the signals travel from the SA node to the AV node.
的在極化。這樣的週期在每次的心跳循環重演。
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The QRS complex marks the firing of the AV node and represents ventricular depolarization:
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- Q wave corresponds to depolarization of the interventricular septum.
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- R wave is produced by depolarization of the main mass of the ventricles.
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- S wave represents the last phase of ventricular depolarization at the base of the heart.
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- Atrial repolarization also occurs during this time but the signal is obscured by the
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large QRS complex.
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The S-T segment reflects the plateau in the myocardial action potential.
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This is when the ventricles contract and pump blood.
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The T wave represents ventricular repolarization immediately before ventricular relaxation,
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or ventricular diastole.
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The cycle repeats itself with every heartbeat.
