Cardiac cycle

Cardiac cycle
OrganismsAnimalia
Biological systemCirculatory system
HealthBeneficial
ActionInvoluntary
MethodBlood is allowed to enter relaxed ventricle chamber from vein through venous valve. Heart muscle contracts ventricle and blood is expelled through arterial valve to artery.
OutcomeCirculation of blood per minute (Humans)
Duration0.6–1 second (Humans)
*Animalia with the exception of Porifera, Cnidaria, Ctenophora, Platyhelminthes, Bryozoan, Amphioxus.
The cycle diagram depicts one heartbeat of the continuously repeating cardiac cycle, namely: ventricular diastole followed by ventricular systole, etc.—while coordinating with atrial systole followed by atrial diastole, etc. The cycle also correlates to key electrocardiogram tracings: the T wave (which indicates ventricular diastole); the P wave (atrial systole); and the QRS 'spikes' complex (ventricular systole)—all shown as color purple-in-black segments.[1][2]
The Cardiac Cycle: Valve Positions, Blood Flow, and ECG
The parts of a QRS complex and adjacent deflections. Re the cardiac cycle, atrial systole begins at the P wave; ventricular systole begins at the Q deflection of the QRS complex.
A heartbeat
Auscultation of a healthy 16-year-old girl's heartbeat
Problems playing this file? See media help.

The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next.[1] It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following a period of robust contraction and pumping of blood, called systole.[1] After emptying, the heart relaxes and expands to receive another influx of blood returning from the lungs and other systems of the body, before again contracting to pump blood to the lungs and those systems.

Assuming a healthy heart and a typical rate of 70 to 75 beats per minute, each cardiac cycle, or heartbeat, takes about 0.8 second to complete the cycle.[2][3] Duration of the cardiac cycle is inversely proportional to the heart rate.[4]

  1. ^ a b c Pollock JD, Makaryus AN (3 October 2022). "Physiology: Cardiac cycle". StatPearls Publishing, US National Library of Medicine. Retrieved 28 March 2024.
  2. ^ a b Silverthorn, DU (10 November 2022). "Constructing the Wiggers diagram using core concepts: a classroom activity". Advances in Physiology Education. 46 (4). doi:10.1152/advan.00046.2022.
  3. ^ Gersh, Bernard J (2000). Mayo Clinic Heart Book. New York: William Morrow. pp. 6–8. ISBN 0-688-17642-9.
  4. ^ Hall JE, Hall ME (2011). Guyton and Hall Textbook of Medical Physiology (12th ed.). Philadelphia: Elsevier. pp. 104–105. ISBN 978-1-4160-4574-8.