Key words and phrases
Systole: When the heart muscle contracts
Diastole: When the heart muscle relaxes
SAN: the SinoAtrial Node (pacemaker). This initiates the heartbeat.
AVN: the AtrioVentricular Node
Myogenic: a muscle that doesn't fatigue, and that functions without signals from the brain.
Cardiac output= heart rate x stroke volume
1. Relaxation of the heart (diastole)
- The blood enters the atria and ventricles from the pulmonary veins and the vena cava.
- The atria are relaxed and fill with blood
- The ventricles are relaxed
- The semi lunar valves are closed, and the left/right atrioventricular valves are open.
- The relaxation of the ventricles draws blood into the atria
2. Contraction of the Atria (atrial systole)
- The atria contract to push the remaining blood into the ventricles.
- The semi lunar vlaves are still closed.
- The left and right atrioventricular valves are open.
- Blood is pumped from the atria to the ventricles. The ventricles remain relaxed
Contraction of the ventricles (Ventricular systole
- The atria relax.
- The semi lunar valves open.
- The atrioventricular valves close.
- The ventricles contract, pushing blood away from the heart.
- The blood is pumped into the pulmonary arteries and the aorta.