Cardiovascular Physiology

Cardiovascular Physiology is the study of the functions and regulatory mechanisms of the heart and blood vessels, describing how blood is propelled through the circulatory system to deliver oxygen and nutrients to tissues and to remove metabolic waste products. It addresses the mechanical, electrical, and neurohormonal processes that generate cardiac output, distribute blood flow, and maintain arterial pressure within limits compatible with organ perfusion.

Cardiac Function

The Cardiac Cycle

The cardiac cycle describes the sequence of mechanical events, alternating between contraction (systole) and relaxation (diastole), that governs the filling and ejection of blood from the atria and ventricles during each heartbeat.

Cardiac Electrophysiology

Electrical activity originating in the sinoatrial node propagates through specialized conduction pathways to coordinate the timed contraction of the atria and ventricles, with disruptions in this activity producing arrhythmias.

Cardiac Output and Its Determinants

Cardiac output, the volume of blood pumped by the heart per minute, is determined by heart rate and stroke volume, the latter influenced by preload, afterload, and myocardial contractility.

Vascular Function

Blood Vessel Structure and Function

Arteries, veins, and capillaries differ in structure to serve distinct roles, with arteries withstanding high pressure, veins acting as capacitance vessels, and capillaries enabling the exchange of gases, nutrients, and fluid with surrounding tissue.

Arterial Pressure Regulation

Arterial pressure is maintained through the interaction of cardiac output and total peripheral resistance, regulated moment-to-moment by baroreceptor reflexes and over longer periods by renal and hormonal mechanisms.

Microcirculation and Exchange

At the level of capillaries, hydrostatic and osmotic pressure gradients govern the movement of fluid and solutes between blood and interstitial tissue, a balance essential for tissue nutrition and fluid homeostasis.

Regulation and Integration

Neural Control of the Circulation

The autonomic nervous system modulates heart rate, contractility, and vascular tone through sympathetic and parasympathetic pathways, allowing rapid adjustment of circulatory function to changing physiological demands.

Hormonal and Renal Regulation

Hormonal systems, including the renin-angiotensin-aldosterone system and natriuretic peptides, act alongside renal mechanisms to regulate blood volume and vascular tone over intermediate to long time scales.

Cardiovascular Response to Physiological Demand

During conditions such as exercise, hemorrhage, or postural change, the cardiovascular system integrates neural, hormonal, and local mechanisms to redistribute blood flow and preserve perfusion to vital organs.