Cardiac Physiology Walkthrough

Cardiac Physiology Walkthrough

Introduction to Cardiac Physiology

Cardiac physiology refers to the study of the heart's function. The heart, a muscular organ located in the chest, is the central component of the cardiovascular system. Its primary role is to pump oxygenated blood throughout the body and return deoxygenated blood to the lungs for reoxygenation. Understanding cardiac physiology is crucial for diagnosing and treating various heart diseases that are prevalent in the United Kingdom.

Cardiac Cycle

The cardiac cycle comprises the sequence of events in a single heartbeat, taking roughly 0.8 seconds to complete. It includes two main phases: systole (when the heart contracts) and diastole (when the heart relaxes). During systole, blood is ejected from the ventricles into the aorta and pulmonary arteries. In diastole, the heart chambers fill with blood from the veins, preparing for the next contraction. Proper coordination of these phases ensures effective blood circulation.

Electrical Activity of the Heart

The heart’s pumping action is regulated by its intrinsic electrical conduction system. The sinoatrial (SA) node, located in the right atrium, acts as the heart’s natural pacemaker, generating electrical impulses that initiate each heartbeat. These impulses propagate through the atrioventricular (AV) node to the ventricles via the bundle of His and Purkinje fibres, resulting in synchronized heart contractions. Electrocardiograms (ECGs) are commonly used in the UK to monitor this electrical activity and detect abnormalities.

Cardiac Output

Cardiac output is a critical parameter, defined as the volume of blood the heart pumps per minute. It is the product of stroke volume (the amount of blood ejected per beat) and heart rate (number of beats per minute). Average cardiac output in a healthy adult is about 5 litres per minute, though it can vary depending on physical activity and medical conditions. Assessing cardiac output can help in understanding heart performance and diagnosing heart failure.

Coronary Circulation

The heart itself requires a steady supply of oxygen-rich blood to function efficiently, which is provided by the coronary arteries. These arteries branch off from the aorta and encircle the heart, delivering essential nutrients to the cardiac tissue. Coronary artery disease, a leading cause of morbidity in the UK, involves the narrowing or blockage of these arteries, reducing blood flow and resulting in angina or myocardial infarction (heart attack).

Regulation of Heart Function

Heart function is finely tuned by various factors, including neural, hormonal, and local mechanisms. The autonomic nervous system, comprising the sympathetic and parasympathetic branches, modulates heart rate and force of contraction. Hormones such as adrenaline and noradrenaline increase heart rate and cardiac output, while local factors like oxygen levels and pH adjust coronary blood flow to match metabolic demands.

Conclusion

A thorough understanding of cardiac physiology is vital for detecting and treating cardiovascular conditions. With heart diseases being a leading health concern in the UK, detailed knowledge of how the heart functions can guide effective interventions and improve patient outcomes. Regular check-ups and monitoring using modern techniques are essential for maintaining cardiovascular health.