Cardiac physiology

Cardiac Physiology

Diagram of blood flow through the heart

Cardiac physiology is the study of the function of the heart and the circulatory system. It encompasses the understanding of how the heart pumps blood, the electrical conduction system, and the regulation of heart rate and blood pressure.

Heart Anatomy and Blood Flow

The heart is a muscular organ responsible for pumping blood throughout the body. It consists of four chambers: the right atrium, right ventricle, left atrium, and left ventricle. Blood flows through the heart in a specific sequence, starting from the right atrium, moving to the right ventricle, then to the lungs for oxygenation, back to the left atrium, and finally to the left ventricle, which pumps it to the rest of the body.

Cardiac Cycle

Animation of the cardiac cycle

The cardiac cycle refers to the sequence of events that occur during one heartbeat. It consists of two main phases: systole and diastole. During systole, the ventricles contract, pumping blood out of the heart. During diastole, the heart relaxes and the chambers fill with blood.

Electrical Conduction System

Diagram of the heart's conduction system

The heart's electrical conduction system controls the heartbeat. It includes the sinoatrial node (SA node), atrioventricular node (AV node), bundle of His, and Purkinje fibers. The SA node, located in the right atrium, acts as the natural pacemaker, initiating electrical impulses that cause the heart to contract.

Cardiac Muscle and Action Potentials

Image of cardiac muscle tissue

Cardiac muscle is a specialized type of muscle found only in the heart. It is striated like skeletal muscle but functions involuntarily. Cardiac muscle cells are connected by intercalated discs, which allow for synchronized contraction. The action potential in cardiac muscle is crucial for initiating contraction and is characterized by a rapid depolarization, plateau phase, and repolarization.

Graph of action potential in cardiac muscle

Electrocardiography (ECG)

Animation of ECG principle

An electrocardiogram (ECG) is a test that measures the electrical activity of the heart. It is used to detect heart abnormalities, such as arrhythmias, myocardial infarction, and other cardiac conditions. The ECG waveform consists of the P wave, QRS complex, and T wave, each representing different phases of the cardiac cycle.

Regulation of Heart Rate

The heart rate is regulated by the autonomic nervous system, which includes the sympathetic nervous system and parasympathetic nervous system. The sympathetic nervous system increases heart rate and contractility, while the parasympathetic nervous system decreases heart rate.

Related Pages

• Cardiology
• Heart disease
• Circulatory system
• Electrophysiology