Cardiac Physiology and Function

The organ, a central component of the circulatory system, is responsible for maintaining systemic perfusion. This is achieved through a rhythmic pumping action, driven by coordinated electrical and mechanical activity.

Circulatory System Integration

It operates as part of a complex network, facilitating the transport of oxygen, nutrients, hormones, and immune cells throughout the body. It also plays a crucial role in waste removal, carrying carbon dioxide and other metabolic byproducts to the lungs and kidneys for excretion.

Cardiac Chambers and Valves

The organ comprises four chambers: the left and right atria, and the left and right ventricles. Blood flow is regulated by four valves: the tricuspid, pulmonary, mitral, and aortic valves. These valves ensure unidirectional blood flow, preventing backflow and maintaining efficient circulation.

Cardiac Cycle

The cardiac cycle encompasses the phases of diastole (relaxation and filling) and systole (contraction and ejection). During diastole, the chambers fill with blood. During systole, the ventricles contract, ejecting blood into the pulmonary artery (from the right ventricle) and the aorta (from the left ventricle).

Electrical Conduction System

Myocardial contraction is initiated and coordinated by a specialized electrical conduction system. This system includes the sinoatrial (SA) node (the natural pacemaker), the atrioventricular (AV) node, the bundle of His, and the Purkinje fibers. Electrical impulses generated by the SA node propagate through the atria, causing atrial contraction, then travel to the AV node and down through the ventricles, triggering ventricular contraction.

Regulation of Cardiac Output

Cardiac output (the volume of blood pumped per minute) is determined by heart rate and stroke volume (the volume of blood ejected with each beat). The rate and force of contraction are modulated by the autonomic nervous system (sympathetic and parasympathetic branches), hormones (e.g., epinephrine), and intrinsic mechanisms (e.g., the Frank-Starling mechanism). Blood volume and vascular resistance also impact its performance.

Myocardial Metabolism

The myocardium (cardiac muscle) requires a constant supply of oxygen and nutrients to function properly. It primarily utilizes fatty acids for energy production, but can also utilize glucose and lactate. Coronary arteries supply blood to the myocardium. Ischemia (reduced blood flow) can lead to myocardial dysfunction and damage.