Question 1

The semilunar valves close to prevent the backflow of blood into the ventricles.

Accepted Answer

This statement is true. The semilunar valves (pulmonary and aortic valves) close during ventricular diastole to prevent the backflow of blood into the ventricles.

Question 2

The functional syncytia of the myocardium are offered by the intercalated discs.

Accepted Answer

The intercalated discs connect cardiomyocytes to each other and provide a pathway for electrical impulses to spread throughout the myocardium, allowing for coordinated contractions and the formation of functional syncytia.

Question 3

The action potential impulse passes through the AV node between the P wave and QRS complex.

Accepted Answer

The action potential impulse passes through the AV node between the P wave and QRS complex. This delay allows for the atria to completely contract before the ventricles begin to contract. Therefore, option A is true.

Question 4

With 2:1 rhythm,the atrial rate is very rapid and the ventricular rate is normal or above normal,whereas with 2:1 block,the atrial rate is normal but the ventricular rate is below normal

Accepted Answer

This statement is true. In a 2:1 rhythm, every second atrial beat is blocked from reaching the ventricles, resulting in a very rapid atrial rate (usually around 150-200 bpm) and a ventricular rate that is either normal or above normal. In contrast, in a 2:1 block, every second atrial beat is conducted to the ventricles, but the ventricles are unable to respond to all of them, resulting in a normal atrial rate and a ventricular rate that is below normal (usually around 50-100 bpm).

Question 5

When ECF K⁺ levels fall below normal,the heart becomes weak,flaccid,and dilated.

Accepted Answer

Potassium is essential for maintaining proper heart function, and low levels can result in weakened, flaccid, and dilated heart muscles.

Question 6

The only point of electrical contact between the atria and the ventricles is the AV valve.

Accepted Answer

The answer of The only point of electrical contact between...

Question 7

The SA node is the pacemaker of the heart.

Accepted Answer

The sinoatrial (SA) node is located in the right atrium and initiates the electrical impulses that regulate the heartbeat, making it the natural pacemaker of the heart.

Question 8

The T wave represents the depolarization of the ventricles.

Accepted Answer

The T wave represents the repolarization of the ventricles, not depolarization.

Question 9

The ECG is an actual recording of cardiac electrical activity.

Accepted Answer

The answer of The ECG is an actual recording of...

Question 10

The ventricles always depolarize at the same rate as the SA node depolarizes.

Accepted Answer

The ventricles do not always depolarize at the same rate as the SA node. The AV node serves as a delay between the atria and ventricles, allowing for complete atrial contraction before ventricular contraction. Therefore, the rate of ventricular depolarization is often slower than the rate of SA node depolarization.

Question 11

Diastole refers to the period of cardiac relaxation.

Accepted Answer

Diastole is the period of cardiac relaxation, during which the heart muscle is resting and filling with blood.

Question 12

Cardiac tamponade refers to failure of the AV node to transmit the action potential from the atria to the ventricles.

Accepted Answer

Cardiac tamponade refers to the accumulation of fluid or blood in the pericardial sac, which can compress the heart and lead to decreased cardiac output. It does not affect the conduction system of the heart.

Question 13

The bundle of His and Purkinje system facilitate the rapid spread of the action potential throughout the ventricles.

Accepted Answer

The bundle of His and Purkinje system are specialized cardiac muscle fibers that facilitate the rapid conduction of electrical impulses through the ventricles, allowing for coordinated contraction and efficient pumping of blood.

Question 14

Atrial repolarization does not occur.

Accepted Answer

Atrial repolarization does occur, but it is not observed on a standard ECG because it occurs at the same time as ventricular depolarization.

Question 15

Most ventricular filling is accomplished during atrial contraction.

Accepted Answer

Most ventricular filling is accomplished during passive ventricular filling, when the pressure in the atria is higher than the pressure in the ventricles and the AV valves are open. Atrial contraction provides an additional boost to ventricular filling, but it only contributes to about 20-30% of the total ventricular filling.

Question 16

The atria and the ventricles contract at the same time to ensure efficient pumping action.

Accepted Answer

The atria contract first, followed by a brief pause before the ventricles contract. This sequential contraction allows for efficient blood flow through the heart.

Question 17

The plateau phase of the action potential in a contractile cardiac muscle cell occurs as a result of activation of slow Ca²⁺ channels.

Accepted Answer

During the plateau phase, slow Ca2+ channels remain open, allowing a prolonged influx of Ca2+ into the cell, which contributes to the sustained contraction of the cardiac muscle cell. These channels are often referred to as L-type channels (Ca²⁺) and are activated by depolarization of the membrane potential.

Question 18

The action potential spreads through the atria by gap junctions,but there are no gap junctions present in the ventricles,so the impulse must be propagated throughout the ventricular myocardium by the bundle of His and Purkinje system.

Accepted Answer

The answer of The action potential spreads through the atria...

Question 19

Ventricular filling occurs more rapidly early in diastole than it does later in diastole.

Accepted Answer

During the early stages of diastole, the ventricles rapidly fill with blood due to the pressure gradient created by the relaxation of the atria and the opening of the atrioventricular (AV) valves. As the ventricles fill, the pressure within them increases, which slows down the rate of filling. Therefore, ventricular filling occurs more rapidly early in diastole than it does later in diastole.

Question 20

Atrial systole lasts throughout ventricular systole.

Accepted Answer

Atrial systole occurs during early ventricular diastole, not systole.

Quiz 7: Cardiac Physiology