Cardiac Cycle and Heart Muscle Function

Cardiac Cycle

Diastole

• Period of heart muscle relaxation
• Lasts approximately 2/3 of the cardiac cycle
• Heart chambers fill with blood
• Atrioventricular valves open, allowing blood to flow from atria to ventricles
• Semilunar valves closed, preventing backflow into pulmonary and aortic arteries

Systole

• Period of heart muscle contraction
• Lasts approximately 1/3 of the cardiac cycle
• Heart chambers pump blood out
• Atrioventricular valves closed, preventing backflow into atria
• Semilunar valves open, allowing blood to flow into pulmonary and aortic arteries

Cardiac Output

• Total volume of blood pumped by the heart per minute
• Calculated by multiplying heart rate (beats per minute) by stroke volume (volume of blood pumped per beat)
• Average cardiac output: 5-6 liters per minute at rest
• Increases with exercise or physical activity

Cardiac Cycle

Diastole

• Lasts approximately 2/3 of the cardiac cycle
• Heart muscle relaxes, allowing heart chambers to fill with blood
• Atrioventricular valves open, facilitating blood flow from atria to ventricles
• Semilunar valves remain closed, preventing backflow into pulmonary and aortic arteries

Systole

• Lasts approximately 1/3 of the cardiac cycle
• Heart muscle contracts, pumping blood out of heart chambers
• Atrioventricular valves close, preventing backflow into atria
• Semilunar valves open, enabling blood flow into pulmonary and aortic arteries

Cardiac Output

• Total volume of blood pumped by the heart per minute
• Calculated by multiplying heart rate (beats per minute) by stroke volume (volume of blood pumped per beat)
• Average cardiac output at rest: 5-6 liters per minute
• Increases during exercise or physical activity

Learn about the cardiac cycle, including the periods of diastole and systole, and how they relate to heart muscle relaxation and contraction. Understand the flow of blood through the heart chambers and valves.