The cardiac cycle is the coordinated sequence of contraction and relaxation that moves blood through the heart. Understanding how pressure changes and valves open or close explains how the heart fills and ejects blood efficiently.
Fluids move from regions of higher pressure to regions of lower pressure. The heart uses this principle: pressure differences move blood through its chambers and vessels, while valves help keep blood flowing in the correct direction.
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What is the cardiac cycle?
The coordinated sequence of filling, contraction, and relaxation during one heartbeat.
What is the atrial kick?
The additional ventricular filling produced by atrial contraction; it normally contributes about 20–30 percent of ventricular filling.
Define EDV and preload.
End diastolic volume (EDV), or preload, is the amount of blood in a ventricle at the end of filling, just before ventricular contraction.
What is the dicrotic notch associated with?
A small dip in a blood pressure tracing associated with brief backward flow as the semilunar valves close.
What is S₁ associated with?
Closure of the mitral and tricuspid valves at the beginning of ventricular contraction.
Quiz questions
Which valve event is associated with the first heart sound, S₁?Answer: Closure of the mitral and tricuspid valves as ventricular contraction begins.
Which valve event is associated with the second heart sound, S₂?Answer: Closure of the aortic and pulmonary valves as ventricular relaxation begins.
Which statement about S₃ is accurate?Answer: It may occur in healthy young people and may warrant evaluation when heard later in life.
What causes a heart murmur?Answer: Turbulent blood flow that produces an unusual heart sound.
How can inhalation affect some heart murmurs?Answer: It may make right-sided murmurs louder by increasing blood flow into the right heart.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.