Anatomy Of The Heart - ECG

The P wave on an ECG represents atrial depolarization, which is the electrical activation of the atria. During atrial depolarization, the electrical signal originates from the SA node (sinoatrial node) and spreads through the atria, causing them to contract. This is the first wave observed on the ECG and indicates the beginning of the cardiac cycle. The other options listed, such as the T wave, QRS complex, SA node, and AV node, do not specifically represent atrial depolarization.

The T wave represents ventricular repolarization in an ECG. After the ventricles contract (depolarization), they need to reset their electrical state in order to prepare for the next contraction. This resetting process is called repolarization, and it is represented by the T wave on the ECG. Therefore, the T wave is the correct answer for this question.

The P-R interval on an ECG represents the time it takes for the electrical signal to travel from the atrium to the ventricle. This interval includes the time it takes for the signal to pass through the atrioventricular (AV) node, which is responsible for delaying the signal to allow for proper filling of the ventricles. Therefore, the P-R interval is a measure of the conduction time between the atria and ventricles, providing information about the integrity of the AV node and any potential conduction abnormalities.

A prolonged P-R interval means that the signal traveling from the atria to the ventricles is abnormally slow. The P-R interval represents the time it takes for the electrical signal to travel from the atria (upper chambers of the heart) to the ventricles (lower chambers of the heart). When this interval is prolonged, it indicates a delay in the conduction pathway, which can result in inefficient pumping of blood and potentially lead to various heart conditions.

The Purkinje fibers are the rapidly conducting fibers that supply the ventricles. These specialized cardiac muscle fibers are responsible for transmitting electrical signals from the AV node to the ventricles, causing them to contract and pump blood. The Purkinje fibers allow for efficient and coordinated contraction of the ventricles, ensuring that blood is effectively pumped out of the heart.

The heart sounds "lubb dupp" are caused by vibrations that occur when the valves in the heart close. When the atrioventricular valves close, it produces the first sound "lubb" and when the semilunar valves close, it produces the second sound "dupp". These vibrations can be heard with a stethoscope and indicate the normal functioning of the heart.

Fibrillation refers to a quivering ventricular muscle that is unable to pump blood effectively. This condition disrupts the normal rhythm of the heart and can lead to serious complications, such as decreased blood flow and potential organ damage. It is often associated with irregular and rapid heartbeats, causing the heart to lose its ability to effectively pump blood throughout the body.

Plasma elevations of CPK, AST, LDH, and troponin are indicative of damage of myocardial cells. These enzymes and proteins are released into the bloodstream when there is damage to the heart muscle. CPK (creatine phosphokinase), AST (aspartate aminotransferase), LDH (lactate dehydrogenase), and troponin are all markers of myocardial injury. Therefore, elevated levels of these substances suggest that there has been damage to the cells of the heart muscle.

The semilunar valves open in response to rising ventricular pressure during ventricular contraction. This is because during ventricular contraction, the pressure within the ventricles increases, causing the blood to be pushed out of the ventricles and into the pulmonary artery and aorta. The semilunar valves, located at the entrances of these arteries, open to allow the blood to flow out of the ventricles and into the arteries. Once the ventricles relax, the pressure within them decreases, causing the semilunar valves to close and prevent backflow of blood into the ventricles.

The Sinoatrial (SA) node, located in the right atrium, is the heart's natural pacemaker. It initiates the electrical impulses that trigger the heart's contractions. These impulses travel through the heart’s conduction system, first to the AV node, then the Bundle of His, and finally to the Purkinje fibers, ensuring synchronized heartbeats. This mechanism controls the rhythm and rate of the heartbeat, making the SA node critical for maintaining proper heart function.

The AV valves close in response to rising ventricular pressure during ventricular contraction. As the ventricles contract, the pressure inside them increases. This increased pressure causes the AV valves, which are located between the atria and ventricles, to close. This closure prevents the backflow of blood from the ventricles into the atria, ensuring that blood flows in the correct direction through the heart.

Repolarization refers to the phase of the cardiac impulse where there is an outflow of potassium ions (K+). During this phase, the cell membrane potential returns to its resting state after depolarization. This is an important process as it allows the heart muscle to relax and prepare for the next cardiac cycle. The correct answer is repolarization.