Pumping mechanism of the heart of a mammalian heart

Here's a breakdown of the mechanism:

1. Electrical Impulse Generation: The process begins with an electrical impulse generated by the sinoatrial (SA) node, often called the heart's natural pacemaker, located in the right atrium.
2. Atrial Contraction (Atrial Systole): The electrical impulse spreads across both atria, causing them to contract. This pushes blood from the right atrium into the right ventricle (deoxygenated blood) and from the left atrium into the left ventricle (oxygenated blood). The tricuspid and mitral (bicuspid) valves open to allow this flow.
3. Ventricular Filling: During atrial contraction, the ventricles are in a relaxed state (diastole) and are filling with blood.
4. Ventricular Contraction (Ventricular Systole): The electrical impulse reaches the atrioventricular (AV) node, located between the atria and ventricles. After a slight delay (allowing the ventricles to fully fill), the impulse travels down the Bundle of His and Purkinje fibers, causing the ventricles to contract forcefully.
   • The pressure generated by ventricular contraction closes the tricuspid and mitral valves (preventing backflow into the atria).
   • The right ventricle pumps deoxygenated blood through the pulmonary valve into the pulmonary artery, leading to the lungs.
   • The left ventricle, the strongest chamber, pumps oxygenated blood through the aortic valve into the aorta, distributing it to the rest of the body.
5. Diastole (Relaxation and Refilling): After contraction, the ventricles relax. As pressure in the ventricles drops, the pulmonary and aortic valves close (preventing backflow from the arteries). The atria begin to fill with blood again, and the cycle restarts.

This continuous, coordinated pumping action ensures efficient circulation of blood throughout the body.