Summary
The sequence of atrial and ventricular contraction (systole) and relaxation (diastole) in each heartbeat.
In depth
Atrial systole fills ventricles; ventricular systole closes AV valves (first sound 'lub') and opens semilunar valves; diastole closes semilunar valves (second sound 'dub'). Cardiac output = heart rate × stroke volume, about 5 L per minute at rest.
Pressure and volume changes are shown in Wiggers diagrams. Heart sounds come from valve closure. Murmurs result from turbulent flow.
Example: stroke volume is about 70 mL.
Frequently asked questions
What is Cardiac Cycle?
The sequence of atrial and ventricular contraction (systole) and relaxation (diastole) in each heartbeat.
Which area of biology covers Cardiac Cycle, and how advanced is it?
Cardiac Cycle is one of the 51 topics in Human Physiology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Frank-Starling Law, Cardiac Conduction System, Blood Pressure.
Can you give an example of Cardiac Cycle?
Pressure curves show valves opening and closing.
What should I learn before Cardiac Cycle?
Work through the Beginner topics in Human Physiology first, such as Homeostasis, Tissues and Organs, Skeletal System, then return to Cardiac Cycle. Intermediate topics assume the Beginner vocabulary.
What topics are related to Cardiac Cycle?
The closest topics to Cardiac Cycle are Frank-Starling Law, Cardiac Conduction System, Blood Pressure, Heart Structure. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Cardiac Cycle?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Cardiac Cycle. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Cardiac Cycle different from Frank-Starling Law?
Cardiac Cycle: The sequence of atrial and ventricular contraction (systole) and relaxation (diastole) in each heartbeat. Frank-Starling Law: Greater ventricular filling stretches the heart and increases the force of the next contraction. Read both side by side and note what each one explains.
How should I study Cardiac Cycle step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Frank-Starling Law and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.