Cardiac Cycle
Cardiac Cycle - Related Videos
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Cardiac Cycle
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2025
The cardiac cycle refers to the sequence of events that occur in the heart from the beginning of one heartbeat to the next. It's characterized by alternating periods of contraction (systole) and relaxation (diastole) of the heart muscles. During the cardiac cycle, blood flow through the heart is regulated entirely by changing pressure gradients. This sequence of events begins with the heart in a state of total relaxation, known as mid-to-late diastole, during which blood passively flows from...
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The Cardiac Cycle
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2025
The heart beats rhythmically in a sequence called the cardiac cycle—a rapid coordination of contraction (systole) and relaxation (diastole). The Process Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and empty blood into the...
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Physiology of the Heart: The Cardiac Cycle
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2025
The cardiac cycle describes the events from one heartbeat to the next. It includes three main phases: diastole, atrial systole, and ventricular systole, all driven by changes in chamber pressures and the function of heart valves. Diastole: The Relaxation Phase During diastole, all four heart chambers relax. The atrioventricular (AV) valves open, and the semilunar valves close. This phase sees the lowest chamber pressures, promoting ventricular filling. Venous blood enters the heart through the...
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Correlation between ECG and Cardiac Cycle
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2025
The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle. A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...
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Cardiac Magnetic Resonance Imaging
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2023
Source: Frederick W. Damen and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana In this video, high field, small-bore magnetic resonance imaging (MRI) with physiological monitoring is demonstrated to acquire gated cine loops of the murine cardiovascular system. This procedure provides a basis for assessing left-ventricular function, visualizing vascular networks, and quantifying motion of organs due to respiration. Comparable small animal...
FAQs
Pressure differences between heart chambers and connected vessels provide the immediate signal for valve movement. As pressure changes during relaxation and contraction, the atrioventricular and semilunar valves open or close, preventing backward flow. This coordination links chamber activity with the direction of blood movement through the pulmonary and systemic circulations.
Valve actions mark important transitions within the heartbeat because they control when blood can move between chambers or leave the ventricles. Their movement also contributes to heart sounds, making sound patterns useful when studying the timing of mechanical events. Abnormal valve function can therefore disturb both flow direction and pumping performance.
The cycle supports two connected routes for blood movement. The pulmonary circulation is served by the heart’s passage of blood toward the lungs, while the systemic circulation carries blood through the rest of the body. Coordinated chamber pressure and valve timing keep these routes connected without allowing the overall flow sequence to reverse.
Students can relate heart sounds and pulse patterns to the alternating mechanical events of relaxation and contraction. Valve movement helps explain the sounds, while ventricular pumping contributes to the pulse pattern detected in the circulation. Studying these features together connects observable signs with the underlying timing of chamber activity.
The repeated filling and pumping actions of the chambers provide a basis for understanding cardiac output and blood pressure. Effective timing allows the heart to receive blood, propel it through the circulations, and maintain the pressure pattern associated with flow. Changes in rhythm or pumping efficiency can alter these outcomes.
The cycle provides a framework for identifying how cardiovascular problems affect normal heart function. Disturbances in rhythm can change event timing, valve problems can interfere with one-way flow, and reduced pumping efficiency can affect circulation. Examining these consequences helps connect cardiovascular conditions with changes in sounds, pulses, blood pressure, or cardiac output.