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What are the two main phases of the cardiac cycle?
What are the two main phases of the cardiac cycle?
Diastole and systole
What occurs during early diastole?
What occurs during early diastole?
The heart muscle relaxes, and the heart chambers fill with blood
What happens during mid-diastole?
What happens during mid-diastole?
The atrioventricular (AV) valves open, allowing blood to flow from the atria to the ventricles
What is the result of atrial contraction?
What is the result of atrial contraction?
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What occurs during isovolumic contraction?
What occurs during isovolumic contraction?
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What happens during rapid ejection?
What happens during rapid ejection?
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What is the result of AV valve closure?
What is the result of AV valve closure?
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What causes the first heart sound (S1 or lub)?
What causes the first heart sound (S1 or lub)?
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What is the relationship between ventricular pressure and the cardiac cycle?
What is the relationship between ventricular pressure and the cardiac cycle?
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What happens to atrial volume during systole?
What happens to atrial volume during systole?
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Study Notes
Phases of the Cardiac Cycle
The cardiac cycle consists of two main phases: diastole and systole.
Diastole
- Early diastole: The heart muscle relaxes, and the heart chambers fill with blood.
- Mid-diastole: The atrioventricular (AV) valves open, allowing blood to flow from the atria to the ventricles.
- Late diastole: The atria contract, pumping additional blood into the ventricles.
Systole
- Isovolumic contraction: The ventricles contract, but the AV valves are closed, and the semilunar valves are closed.
- Rapid ejection: The semilunar valves open, and blood is rapidly ejected from the ventricles into the aorta and pulmonary arteries.
- Reduced ejection: The ventricles continue to contract, but the rate of ejection slows down.
Key Events
- Atrial contraction: The atria contract, pumping additional blood into the ventricles.
- Ventricular contraction: The ventricles contract, pumping blood out of the heart.
- AV valve closure: The AV valves close, preventing backflow from the ventricles to the atria.
- Semilunar valve closure: The semilunar valves close, preventing backflow from the aorta and pulmonary arteries to the ventricles.
Pressure and Volume Changes
- Ventricular pressure: Increases during systole, decreases during diastole.
- Atrial pressure: Decreases during systole, increases during diastole.
- Ventricular volume: Decreases during systole, increases during diastole.
- Atrial volume: Increases during systole, decreases during diastole.
Heart Sounds
- S1 (lub): The sound of the AV valves closing.
- S2 (dub): The sound of the semilunar valves closing.
Phases of the Cardiac Cycle
- The cardiac cycle consists of two main phases: diastole and systole.
Diastole
- Heart muscle relaxes and heart chambers fill with blood during early diastole.
- Atrioventricular (AV) valves open, allowing blood to flow from atria to ventricles during mid-diastole.
- Atria contract, pumping additional blood into ventricles during late diastole.
Systole
- Ventricles contract, but AV valves are closed, and semilunar valves are closed during isovolumic contraction.
- Semilunar valves open, and blood is rapidly ejected from ventricles into aorta and pulmonary arteries during rapid ejection.
- Ventricles continue to contract, but rate of ejection slows down during reduced ejection.
Key Events
- Atrial contraction pumps additional blood into ventricles.
- Ventricular contraction pumps blood out of the heart.
- AV valve closure prevents backflow from ventricles to atria.
- Semilunar valve closure prevents backflow from aorta and pulmonary arteries to ventricles.
Pressure and Volume Changes
- Ventricular pressure increases during systole and decreases during diastole.
- Atrial pressure decreases during systole and increases during diastole.
- Ventricular volume decreases during systole and increases during diastole.
- Atrial volume increases during systole and decreases during diastole.
Heart Sounds
- S1 (lub) is the sound of AV valves closing.
- S2 (dub) is the sound of semilunar valves closing.
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Description
Learn about the two main phases of the cardiac cycle, diastole and systole, and their sub-phases in the heart's blood pumping process.
