One heartbeat is a cycle of squeezing (systole) and resting (diastole) that repeats over and over. Step through the phases and hear where the “lub-dub” comes from.
Atrial systole
The cardiac cycleone heartbeat
The phases
📷 Reference image
A real labeled picture to compare with the activity above.
The Cardiac Cycle — OpenStax, CC BY 3.0 (via Wikimedia Commons)
