Cardiac Cycle: steps

Question 1

Atrial Systole

Answer 1

the end of diastole

atrium contracts
volume in ventricle tops off
“a” wave occurs when atrium contracts → increasing atrial pressure

P wave occurs → due to atrial depolarization

heart sound 4 (S4) is associated with the end of atrial emptying after atrial contraction

Question 2

Isovolumic contraction

Answer 2

The beginning of systole

atrioventricular (AV) valves close at beginning of this phase

Q-T interval on ECG

the interval between the closing of the AV valves and the opening of the semilunar valves (aortic and pulmonary valves)

pressure in the ventricles exceeds pressure in atria

ventricular volume does not change

ventricular pressure increases

QRS complex

First heart sound

Question 3

Rapid Ejection

Answer 3

ventricular systole

aortic and pulmonary valves open at the beginning of this phase

ventricles continue contracting

pressure in ventricles exceeds pressure in aorta and pulmonary arteries

blood exits ventricles → decreasing ventricular volume rapidly

blood enters arteries → pressure builds until flow reaches peak

“c” wave of atrial pressure is not discernible

atrial pressure increases → contraction of right ventricle pushes tricuspid valve open

Question 4

Reduced ejection

Answer 4

end of systole

aortic and pulmonary valves close at the end of this phase

after peak in ventricular and arterial pressures, blood flows out of ventricles decreases and ventricular volume decreases

pressure in ventricles falls below pressure in arteries → blood in arteries flows back to ventricles → valves close

T wave occurs

Question 5

Isovolumic relaxation

Answer 5

beginning of diastole

AV valves are closed at beginning of this phase

atrial pressure rising → atrium in diastole is filling with blood

“v” wave → due to back flow of blood when it hits closed AV valve

ventricular pressure continues to drop

ventricular volume is at the minimum

2nd heart sound occurs

Question 6

Rapid ventricular filling

Answer 6

AV valves open, blood flows from atria to ventricles

ventricular volume increases rapidly

3rd heart sound

Question 7

Reduced ventricular filling

Answer 7

diastasis

ventricular volume increases more slowly

ventricles continue to fill with blood