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Questions and Answers
What happens to ventricular pressure at the end of systole?
What happens to ventricular pressure at the end of systole?
What occurs at the beginning of isovolumic relaxation?
What occurs at the beginning of isovolumic relaxation?
Which event indicates the end of the isovolumic relaxation phase?
Which event indicates the end of the isovolumic relaxation phase?
What is observed in the phonogram during isovolumic relaxation?
What is observed in the phonogram during isovolumic relaxation?
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How does left atrial pressure compare to left ventricular pressure during diastole?
How does left atrial pressure compare to left ventricular pressure during diastole?
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What occurs at the beginning of the ventricular contraction phase?
What occurs at the beginning of the ventricular contraction phase?
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What remains unchanged during reduced ventricular ejection?
What remains unchanged during reduced ventricular ejection?
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When does the first heart sound (S1) occur in relation to the QRS complex?
When does the first heart sound (S1) occur in relation to the QRS complex?
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Which of the following statements is true about blood flow during the last two-thirds of the ejection phase?
Which of the following statements is true about blood flow during the last two-thirds of the ejection phase?
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What happens to ventricular pressure at the end of the ejection phase?
What happens to ventricular pressure at the end of the ejection phase?
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What initiates the closure of the mitral and tricuspid valves?
What initiates the closure of the mitral and tricuspid valves?
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What drives the continued flow of blood after the pump has stopped?
What drives the continued flow of blood after the pump has stopped?
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How does ventricular volume change during the slow ejection phase?
How does ventricular volume change during the slow ejection phase?
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Which sequence correctly traces the path of an action potential in the heart?
Which sequence correctly traces the path of an action potential in the heart?
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What role do the atria serve in the cardiac cycle?
What role do the atria serve in the cardiac cycle?
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What is the significance of the 0.1 second delay when passing the cardiac impulse from atria to ventricles?
What is the significance of the 0.1 second delay when passing the cardiac impulse from atria to ventricles?
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During the cardiac cycle, which of the following is NOT a characteristic of the ventricles?
During the cardiac cycle, which of the following is NOT a characteristic of the ventricles?
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Which of the following best describes the cardiac cycle?
Which of the following best describes the cardiac cycle?
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What happens to the blood in the ventricles during a strong ventricular contraction?
What happens to the blood in the ventricles during a strong ventricular contraction?
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What component of the heart sequence represents the 'pacemaker'?
What component of the heart sequence represents the 'pacemaker'?
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What is primarily illustrated by the Wiggers diagram in relation to the cardiac cycle?
What is primarily illustrated by the Wiggers diagram in relation to the cardiac cycle?
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What causes the second heart sound?
What causes the second heart sound?
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What does the dicrotic notch on the aortic pressure represent?
What does the dicrotic notch on the aortic pressure represent?
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During which phase of the cardiac cycle is aortic pressure highest?
During which phase of the cardiac cycle is aortic pressure highest?
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What does the P wave of the ECG represent?
What does the P wave of the ECG represent?
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What volume of blood is typically pumped out by each ventricle during a cardiac cycle?
What volume of blood is typically pumped out by each ventricle during a cardiac cycle?
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Atrial systole is preceded by which electrical event?
Atrial systole is preceded by which electrical event?
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Which statement about ventricular systole is false?
Which statement about ventricular systole is false?
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What happens during the isovolumic contraction phase?
What happens during the isovolumic contraction phase?
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What primarily causes the opening of the mitral valve during rapid ventricular filling?
What primarily causes the opening of the mitral valve during rapid ventricular filling?
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During which phase does the third heart sound (S3) typically occur?
During which phase does the third heart sound (S3) typically occur?
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What happens to the ventricular volume during the diastasis phase?
What happens to the ventricular volume during the diastasis phase?
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What is the ejection fraction typically considered to be during rapid ventricular filling?
What is the ejection fraction typically considered to be during rapid ventricular filling?
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What leads to a gradual drop in aortic pressure during rapid ventricular filling?
What leads to a gradual drop in aortic pressure during rapid ventricular filling?
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What is characteristic of the ECG during the rapid ventricular filling phase?
What is characteristic of the ECG during the rapid ventricular filling phase?
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In which phase does only a small amount of blood enter the ventricles?
In which phase does only a small amount of blood enter the ventricles?
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What is the relationship between atrial pressure and ventricular pressure at the start of rapid ventricular filling?
What is the relationship between atrial pressure and ventricular pressure at the start of rapid ventricular filling?
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Study Notes
Cardiac Cycle Overview
- The cardiac cycle comprises a sequence of mechanical and electrical events repeating with each heartbeat.
- Initiated by an action potential from the sinoatrial (SA) node, functioning as the heart's pacemaker.
- The impulse travels from the superior vena cava, stimulates both atria, and then transmits through the A-V bundle to the ventricles.
- A 0.1-second delay in impulse transmission allows atrial contraction to precede ventricular contraction.
Atria and Ventricles
- Atria serve as primer pumps, sending blood into the ventricles before the stronger ventricular contractions occur.
- Ventricles generate most cardiac power with a typical end-diastolic volume (EDV) of 120 ml.
- During ejection, ventricular pressures rise above atrial pressures, opening semilunar valves while closing atrioventricular valves.
Phases of the Cardiac Cycle
-
Isovolumic Relaxation:
- After systole, ventricles repolarize and relax, decreasing intraventricular pressures.
- Ventricular pressure drops below atrial pressure, causing the mitral valve to open, allowing blood to flow into the ventricles.
-
Rapid Ventricular Filling:
- Blood rapidly fills the ventricles once the mitral valve opens, leading to a steep increase in ventricular volume.
- Aortic pressure gradually declines as the aortic valve remains closed.
- A third heart sound (S3) may be heard due to turbulent filling.
-
Diastasis (Slow Ventricular Filling):
- Characterized by a slower influx of blood into the ventricles despite the mitral valve being open.
- The ventricular volume reaches a plateau, with minimal blood flow from the left atrium to the left ventricle.
Heart Sounds and Pressure Changes
- The first heart sound (S1) is associated with closure of the mitral and tricuspid valves at the peak of the R wave on an ECG.
- The second heart sound (S2) is caused by the closure of the semilunar valves.
- The dicrotic notch on the aortic pressure graph results from the closure of the aortic valve.
Key Cardiac Measurements
- Ejection Fraction (EF): The fraction of end-diastolic volume ejected during each heartbeat, averaging approximately 60% (0.6).
- Each ventricle pumps about 70 ml of blood during the cardiac cycle.
- Atrial depolarization is represented by the P wave on an ECG.
Phases of Cardiac Cycle Pressures
- Aortic pressure is highest during reduced ventricular ejection.
- Diastole is marked by increased atrial and ventricular pressures due to continuous venous return.
Important Facts
- The degree of ventricular filling during relaxation and rapid filling is crucial for efficient cardiac output.
- The cardiac cycle incorporates electrical events (action potentials) and mechanical events (contractions and relaxations) to maintain blood circulation effectively.
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Description
Test your understanding of the cardiac cycle, including the roles of the atria and ventricles. Focus on the phases of the cardiac activity, starting from the SA node to the contraction mechanisms. Assess your knowledge of how electrical impulses control heart function.
