The cardiac cycle

Cardiac cycle - The sequence of events in one full beat of the heart.

Action of atrio-ventricular valves

• After ventricular systole (contraction), the ventricular walls relax and recoil.
• Pressure drops in ventricles below the pressure in the atria.
• Blood in atria pushes atrio-ventricular valves open.
• Blood flows through atria and into ventricles, causing the pressure in the atria and ventricles to rise.
• Valves remain open whilst atria contract and close when they relax.
• During ventricular systole, the pressure of the blood in ventricles rises. When it rises above atrial pressure, the blood starts to move upwards. This fills the valve pockets, keeping them closed.
• Tendinous cords attached to the valves prevent them from turning inside out, preventing blood from flowing back into the atria.

Action…