The Cardiac Cycle Quiz

Systole represents the phase of the cardiac cycle when the ventricles contract and eject blood into the arteries. This phase is characterized by increased pressure in the ventricles, causing the semilunar valves to open and blood to be pumped out of the heart. During systole, the atria are relaxed and filling with blood for the next cycle.

The correct answer is "Cardiac Cycle refers to the sequence of events that occur during one complete heartbeat." This definition accurately describes the cardiac cycle, which includes the contraction of the atria, the contraction and relaxation of the ventricles, and the circulation of blood in the heart. It encompasses all the necessary events that take place during a single heartbeat.

Diastole represents ventricular relaxation and filling phases. During diastole, the ventricles of the heart are relaxed and blood is allowed to flow into them from the atria. This is the phase where the heart is filling with blood in preparation for the next contraction. Systole, on the other hand, represents the contraction phase of the ventricles where blood is pumped out of the heart. Plateau phase and latch state are not terms commonly used to describe the cardiac cycle.

During ventricular systole, the ventricles contract to pump blood out of the heart. The atrioventricular valves close to prevent backflow of blood into the atria. The semilunar valves open to allow blood to be ejected into the arteries. However, the statement "The ventricles relax" is not true for ventricular systole. Ventricular relaxation occurs during ventricular diastole, the period of the cardiac cycle when the ventricles are filling with blood.

The correct answer is 0.80 seconds. An average heartbeat, or cardiac cycle, refers to the time it takes for the heart to complete one full cycle of contraction and relaxation. The normal resting heart rate for adults is around 60-100 beats per minute, which translates to approximately 0.60-1.00 seconds per beat. Therefore, 0.80 seconds falls within this range and is a reasonable estimate for the duration of an average heartbeat.

During the Mid-to-Late Diastole, the heart is in complete relaxation, meaning that the heart muscles are not contracting. This relaxation allows the heart chambers to fill with blood, resulting in a low pressure within the heart. Therefore, the statement that the pressure in the heart is low during this phase is true.

During systole, the ventricles contract and pump blood out of the heart. This contraction causes an increase in pressure within the ventricles, which leads to a decrease in ventricular blood volume. Therefore, at the beginning of systole, the ventricular blood volume is higher compared to later stages of the cardiac cycle such as diastole or mid-to-late diastole.

During ventricular diastole, the semilunar valves close. This is because ventricular diastole is the phase of the cardiac cycle where the ventricles relax and fill with blood. As the ventricles relax, the pressure in the ventricles decreases, causing the blood to flow back towards the ventricles. The closure of the semilunar valves prevents the backflow of blood into the ventricles, ensuring that the blood flows in the correct direction, from the atria to the ventricles and then out to the arteries.

Passive Filling is the first phase in the cardiac cycle. During this phase, the heart is relaxed, and the blood flows passively from the atria to the ventricles. The atria are filled with blood from the veins, and as the ventricles expand, they create a pressure gradient that allows the blood to flow into the ventricles. This phase is crucial for filling the ventricles with blood before the next phase of the cardiac cycle, ventricular isovolumic contraction, begins.

This statement is false because ventricular filling is primarily due to the relaxation of the ventricles, not atrial contraction. During diastole, the ventricles relax and blood flows passively from the atria into the ventricles due to the pressure difference. Atrial contraction, also known as atrial systole, occurs just before ventricular systole and helps to push the remaining blood into the ventricles, but it does not account for most of the ventricular filling.

The dicrotic notch involves the aortic pressure. The dicrotic notch is a small dip or notch that occurs in the aortic pressure waveform during ventricular diastole. It is caused by the closure of the aortic valve, which briefly interrupts the flow of blood from the left ventricle into the aorta. This interruption creates a small dip in the aortic pressure waveform, known as the dicrotic notch. Therefore, the correct answer is Aortic pressure.

The correct order of the three phases of the Cardiac Cycle is Mid-to-Late Diastole, Ventricular Systole, Early Diastole. During Mid-to-Late Diastole, the heart is relaxed and filling with blood. Ventricular Systole follows, where the ventricles contract, forcing blood out of the heart. Finally, Early Diastole occurs, which is a brief period of relaxation before the next cycle begins.

The duration of the beats is 0.6. This can be calculated by dividing 60 seconds (the number of seconds in a minute) by the heart rate of 90 beats per minute. This calculation gives us 0.6 seconds, which represents the duration of each beat.