Question

Place the events of the cardiac cycle in order. (Note that not all events will be listed for the complete cycle.)

a Pressure drops in ventricles due to decreased volume and ventricular relaxation.
b AV valves open due to pressure changes, blood flows into ventricles.
c QRS complex is generated by depolarization of ventricles.
d P-wave is generated by depolarization of atria.
e Semilunar valves close, stopping flow of blood out of the ventricle.
f Blood flows out of ventricles into aorta and pulmonary arteries.
g Ventricles contract, increasing ventricular pressure
h Atria contract, increasing atrial pressure and pumping small amount of blood into ventricles.
i AV valves close due to pressure changes.
j Semilunar valves open due to pressure changes.

Answer 1

The cardiac cycle starts with the depolarization of atria (P-wave), followed by the atria contracting, the closing of AV valves, the depolarization of ventricles (QRS complex), ventricular contracture, the opening, then closing of semilunar valves as blood is pumped out, and ends with the relaxation of ventricles causing pressure to drop and AV valves to open, allowing blood to flow in.

Step-by-step explanation:

Order of Events in the Cardiac Cycle

The cardiac cycle is a complex series of events that involve the contraction and relaxation of the heart chambers to facilitate blood flow. The following are the events placed in their correct order:

1. P-wave is generated by depolarization of the atria (event d).
2. Atria contract, increasing atrial pressure and pumping a small amount of blood into ventricles (event h).
3. AV valves close due to pressure changes (event i).
4. QRS complex is generated by depolarization of the ventricles (event c).
5. Ventricles contract, increasing ventricular pressure (event g).
6. Semilunar valves open due to pressure changes, and blood flows out of ventricles (event j).
7. Blood flows out of ventricles into the aorta and pulmonary arteries (event f).
8. Semilunar valves close, stopping the flow of blood out of the ventricles (event e).
9. Pressure drops in ventricles due to decreased volume and ventricular relaxation (event a).
10. AV valves open due to pressure changes, and blood flows into ventricles (event b).

These events correspond to the various phases of the cardiac cycle, beginning with atrial systole, followed by ventricular systole, and concluding with ventricular diastole. The cycle is regulated by the heart's electrical system, which is represented on an electrocardiogram (ECG) by the P-wave, QRS complex, and other features.