Heart of the Matter: EKG Essentials for Medical Assistants-Part II Cardiac Anatomy and Physiology

Part II Cardiac Anatomy and Physiology

Pdf Summary

The heart consists of four chambers: two upper atria (right and left) and two lower ventricles (right and left). Oxygen-poor blood enters the right atrium, moves to the right ventricle, and is pumped to the lungs for oxygenation. Oxygen-rich blood returns to the left atrium, moves to the left ventricle, and is pumped out to the body. Heart valves (tricuspid, mitral, pulmonic, and aortic) act as one-way doors to ensure blood flows correctly through the chambers and out to the lungs or body.<br /><br />The cardiac conduction system controls heartbeat rhythm through electrical impulses. The sinoatrial (SA) node in the right atrium is the natural pacemaker, initiating impulses around 60 to 100 beats per minute. The atrioventricular (AV) node delays the signal to allow ventricles to fill with blood. The bundle of His carries the signal down the heart’s septum, dividing into two branches that transmit the impulse to the ventricles via Purkinje fibers. This electrical activity causes heart muscle cells to contract and reset in a repetitive cycle, coordinating consistent heartbeats. Disruptions in this process lead to arrhythmias.<br /><br />Axis determination is a method of evaluating the heart’s electrical activity direction on an electrocardiogram (EKG), primarily using leads I and aVF. A normal axis indicates proper electrical signal flow, while an abnormal axis suggests potential cardiac issues. Understanding these fundamentals helps medical assistants grasp EKG essentials, aiding in cardiovascular assessment and care.

Keywords

heart chambers

atria

ventricles

heart valves

cardiac conduction system

sinoatrial node

atrioventricular node

bundle of His

Purkinje fibers

electrocardiogram axis