Cardiac Cycle and Heart Sounds

Question 1

Cardiac cycle

Answer 1

-events in one heart beat (0.8s, 75 beats/minute)
-in a healthy heart, atria contract simultaneously, then as they relax, ventricles begin to contract
(Atrial diastole, atrial systole, isovolumetric contraction, ventricular systole, isovolumetric relaxation

Question 2

Atrial diastole

Answer 2

• heart relaxes
• low BP
• blood flows passively from atria to ventricles
• closed semilunar valves
• atria contracts

Question 3

Atrial systole

Answer 3

• atria contract
• ventricles remain in diastole
• blood is forced into ventricles to complete ventricular filling
• closed semilunar valves

Question 4

Isovolumetric contraction (lub)

Answer 4

• atrial systole ends
• ventricular systole begins
• intraventricular pressure rises
• AV valves close, all valves closed

Question 5

Ventricular systole

Answer 5

• ventricles continue to contract
• intraventricular pressure > pressure in arteries
• semilunar valves open
• AV valves closed, atria relaxed filling with blood

Question 6

Isovolumetric relaxation (dup)

Answer 6

• ventricular diastole begins
• pressure falls below that in major arteries
• semilunar valves close, all valves closed
• when atrial pressure > intraventricular pressure, AV valves open