1) The cardiac cycle describes the events of one complete heartbeat, including atrial contraction, ventricular contraction and relaxation. 2) The cardiac cycle begins with mid-to-late diastole as blood flows into the ventricles, followed by ventricular systole where the ventricles contract and push blood out. 3) Cardiac output is the amount of blood pumped by the heart per minute and is calculated by multiplying heart rate by stroke volume, which is the amount of blood pumped per ventricular contraction.

1. Professor Md.Toufiqur Rahman
MBBS, FCPS, MD, FACC, FESC, FRCP, FSCAI,
FCCP,FAPSC, FAPSIC, FAHA,FACP,FASE
Professor and Head of Cardiology
Colonel Malek Medical College , Manikganj
.
drtoufiq19711@yahoo.com
Physiology of
Cardiovascular System

12. The Heart’s Cardiac Cycle
• Atria contract simultaneously
• Atria relax, then ventricles contract
• Systole = contraction
• Diastole = relaxation

17. Heart Contractions
• Contraction is initiated by the sinoatrial node
• Sequential stimulation occurs at other autorhythmic cells

18. Filling of Heart Chambers – the Cardiac
Cycle

25. The Heart: Cardiac Cycle
• Cardiac cycle – events of one complete heart
beat
– Mid-to-late diastole – blood flows into ventricles
– Ventricular systole – blood pressure builds before
ventricle contracts, pushing out blood
– Early diastole – atria finish re-filling, ventricular
pressure is low

29. The Heart: Cardiac Output
• Cardiac output (CO)
– Amount of blood pumped by each side of the
heart in one minute
– CO = (heart rate [HR]) x (stroke volume [SV])
• Stroke volume
– Volume of blood pumped by each ventricle in one
contraction

47. Cardiac Output Regulation