6 Questions
During which phase of the cardiac cycle does blood flow from the atria into the ventricles, with the semilunar valves closed?
Atrial diastole
What is the term for the amount of blood left in the ventricles after the stroke volume is pushed out?
End systolic volume (ESV)
Which phase of the cardiac cycle involves the relaxation of the ventricles, with both semilunar and atrioventricular valves closed?
Ventricular diastole
What happens during isovolumic contraction in the cardiac cycle?
Atrioventricular valves close
What characterizes stroke volume in the context of the cardiac cycle?
The amount of blood pushed out by the ventricles
In which phase of the cardiac cycle does blood flow towards the atria, causing the atrioventricular valves to close?
Atrial systole
Study Notes
Cardiac Cycle
- The cardiac cycle begins at atrial contraction and ends with ventricular relaxation.
- The cardiac cycle consists of two main phases: systole and diastole.
- Systole is the phase where the heart pumps blood into circulation.
- Diastole is the phase where the heart chambers are relaxed and filling with blood.
Cardiac Cycle Phases
- The cardiac cycle starts with atria and ventricles relaxed, allowing blood to flow into atria and ventricles (70% - 80%).
- Semilunar valves are closed during this phase.
- Atrial systole occurs when the atria contract from the superior portion following depolarization (P wave), also known as the "atrial kick".
- Atrial diastole is the phase where the atrial muscles relax as the ventricles begin to contract.
- Ventricular systole is the phase where the blood in the ventricles is at the end diastolic volume (EDV) or preload, and it flows towards the atria, forcing the atrioventricular valves to close (isovolumic contraction).
- During ventricular systole, pressure increases, forcing the semilunar valves open.
- Ventricular diastole is the phase where the ventricles relax (T wave), and the semilunar valves close, while the atrioventricular valves are also closed (isovolumic ventricular relaxation phase).
- In the second phase of ventricular diastole, the atrioventricular valves open.
Key Cardiac Cycle Measurements
- Stroke volume is the amount of blood pushed out by the ventricles, normally 70-80 mL.
- End systolic volume (ESV) is the amount of blood left in the ventricles after the stroke volume is pushed out.
Learn about the different phases of the cardiac cycle, from atrial contraction to ventricular relaxation. Understand the importance of systole and diastole in pumping blood and filling chambers. Explore the sequence of events during atrial systole and diastole.
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