Cardiac Action Potential and ECG Quiz

Heart Structure and Function

• The myocardium consists of the main muscle layer of the heart.
• The coronary arteries are located in the epicardium, the outermost layer of the heart's walls.
• The obtuse marginal branch of the left circumflex coronary artery supplies the lateral wall of the left ventricle.

Blood Flow and Oxygen Demand

• During physical stress, blood flow in coronary vessels increases to meet the increased oxygen demand.
• If the coronary artery is occluded by more than 70%, resting blood flow becomes insufficient to meet oxygen demand.
• The heart plays a crucial role in supplying blood to the body, and any disruption in blood flow can lead to tissue hypoxia.

Tissue Hypoxia and Coronary Occlusion

• The primary cause of tissue hypoxia in the myocardium during activities like running is the inability of the coronary circulation to meet the increased oxygen demand.
• Atherosclerosis, a process of plaque buildup, may result in complete occlusion of the vessel supplying a specific region of the myocardium.

Action Potentials in Cardiac Cells

• The main characteristic of Phase 0 of the fast-response action potential in cardiac cells is a rapid depolarization due to the influx of sodium ions.
• Fast-response action potentials occur in atrial and ventricular myocardial fibers as well as Purkinje fibers.
• The plateau phase in the fast-response action potential is primarily maintained by the influx of calcium ions.
• The release of a large amount of calcium into the cytosol from the sarcoplasmic reticulum during myocardial contraction is triggered by the depolarization of the sarcolemma.
• Ventricular contraction is sustained throughout the action potential during Phase 2.
• Potassium ions are mainly responsible for repolarization during Phase 3 of the fast-response action potential.
• 'Restoration of ionic concentrations' during Phase 4 is primarily mediated by the Na+/K+ ATPase pump.
• The 'ATP-driven Ca++ Pump' is responsible for the reuptake of calcium ions into the sarcoplasmic reticulum during Phase 4.

Test your knowledge of cardiac action potential and its relation to ECG with this quiz. Topics include heart chambers, myocardial layers, coronary arteries, and coronary anatomy.