SCIENCE The Cardiac Cycle, Heart Sounds, and Blood Pressure

Cardiac Cycle

refers to the sequence of events during one heartbeat, it includes the filling and pumping of blood in and out of the heart

Diastole

relaxation of all heart chambers

Atrial systole

contraction of the atria

Ventricular systole

contraction of the ventricles

Diastole Phase

0.4 seconds

Atrial Systole

0.1 second

Ventricular Systole

0.3

Lub

 Caused by ventricular contraction and closure of AV valves

Lub

Softer pitch, longer duration

Dub

Caused by closure of semilunar valves

Dub

Higher pitch, shorter duration

Blood pressure

force of circulating blood on vessel walls

Systolic

during heart contraction, highest during a hearbeat

Diastolic

during heart relaxation, drops between beats

60–70 beats per minute

Normal resting heart rate

Blood pressure

pushes blood through vessels from the heart

Pulse

felt as arteries expand with each heartbeat

Pulse

strongest near the surface where arteries are close to the skin