unit 2, group 4: Mitchel, Nou, and Rita

Question 1

What is the first phase of the cardiac cycle?

Answer 1

Atrial Systole

• AV valves open
• Semilunar valves closed
• Systolic contraction of atria adds final volume to ventricles (end-diastolic volume)

Question 2

What happens during the 2nd phase of the cardiac cycle?

Answer 2

Isovolumetric contraction

• All valves closed (first heart sound, S1)
• Pressure in ventricles increases with systolic contraction

Question 3

What happens during the 3rd phase of the cardiac cycle?

Answer 3

Rapid ejection

-Semilunar valves open due to increased ventricular systolic pressure

Question 4

What happens during the 4th phases cardiac cycle?

Answer 4

Reduced ejection

• ventricles finish systole
• total ejection from phases 3 and 4 is approx. 2/3 of the blood volume in ventricles (Stroke volume)

Question 5

What is the 5th phase of the cardiac cycle?

Answer 5

Isovolumetric relaxtion

• All valves closed (second heart sound, S2) as pressure in arteries exceeds that of ventricles
• 1/3 of blood left in ventricles: end-systolic volume

Question 6

What is the 6th phases of the cardiac cycle?

Answer 6

Rapid ventricular filling

• AV valves open due to pressure of venous blood
• both atria and ventricles fill with blood