The Cardiac Cycle Phases and Their Role in Heart Function

The cardiac cycle consists of systole and diastole, involving ventricular contraction and relaxation. Blood flows from high to low pressure, with valves opening and closing based on pressure gradients. The cycle starts with the SA node firing, leading to atrial contraction and ventricular filling. Systole begins with ventricular depolarization and isovolumetric contraction, followed by blood ejection. Diastole starts with semilunar valve closure, leading to isovolumetric relaxation and ventricular filling, completing the cycle.

What are the two main phases of the cardiac cycle?

• Contraction and Relaxation

• Systole and Diastole

• Depolarization and Repolarization

• Atrial and Ventricular

What triggers the start of the cardiac cycle?

• The contraction of the ventricles

• The closing of the AV valves

• The opening of the semilunar valves

• The firing of the SA node

What is the significance of the P-wave on an ECG?

• It marks the beginning of systole

• It shows the closing of semilunar valves

• It represents atrial depolarization

• It indicates ventricular depolarization

What marks the beginning of systole?

• The T-wave on the ECG

• The firing of the SA node

• The closing of the AV valves

• The opening of the semilunar valves

During which phase do the ventricles contract without changing volume?

• Atrial contraction

• Isovolumetric contraction

• Rapid ejection

• Ventricular filling

What happens when ventricular pressures exceed aortic and pulmonary pressures?

• The AV valves open

• The semilunar valves close

• Blood is ejected from the ventricles

• The atria contract

What marks the end of systole?

• The opening of the AV valves

• The closing of the semilunar valves

• The T-wave on the ECG

• The firing of the SA node

What occurs during the isovolumetric relaxation phase?

• Ventricular volume changes

• All valves are closed

• Ventricular pressure increases

• Blood is ejected from the ventricles

When do the AV valves open during the cardiac cycle?

• When atrial pressures exceed ventricular pressures

• When ventricular pressures exceed aortic pressures

• During ventricular depolarization

• At the end of systole

What completes the ventricular filling phase?

• The opening of the AV valves

• The closing of the semilunar valves

• The contraction of the atria

• The firing of the SA node