Section 4 Flashcards
What does the cardiac cycle consist of, and what are the alternating periods called?
The cardiac cycle consists of alternating periods of contraction (systole) and relaxation (diastole).
Why is the focus often on just the left side of the heart when discussing the cardiac cycle?
Both the right and left sides contract at the exact same time, so the process is the same; the focus on the left side simplifies discussion, differing only in valve and blood vessel names on the right side.
What happens just before the start of the P-wave of the electrocardiogram during the cardiac cycle?
Blood is flowing from the pulmonary veins into the left atrium, and, as the AV valve is open, blood is passively flowing into the left ventricle.
What occurs when the atria contract (P wave) during the cardiac cycle, and what is the impact on the left ventricle?
When the atria contract, pressure is generated in the left atria, squeezing blood into the left ventricle to increase both left ventricular blood volume and pressure.
What is happening during the isovolumetric contraction phase of the cardiac cycle?
Isovolumetric contraction is the period when both the AV and aortic valves are closed, and the pressure in the left ventricle increases, preventing backward blood flow.
What triggers the opening of the aortic valve during the cardiac cycle, and what happens as a result?
When the pressure generated in the left ventricle becomes larger than that in the aorta, the aortic valve opens, allowing blood to be squeezed from the left ventricle into the aorta.
What marks the end of the isovolumetric contraction phase in the cardiac cycle?
The opening of the aortic valve marks the end of the isovolumetric contraction phase.
When does the first heart sound (lub) occur, and what is the significance of this sound?
The first heart sound occurs when the AV valves close, marking the beginning of ventricular systole.
What causes the second heart sound (dub), and what does it signify?
The second heart sound occurs when the semilunar valves close, indicating the onset of ventricular diastole.
How does a stenotic valve affect heart sounds, and what causes this alteration?
A stenotic valve, which does not open fully, increases blood velocity and turbulent flow, causing a whistling-like sound in the heart.
What is the effect of an insufficient or leaky valve on heart sounds, and what causes this alteration?
An insufficient valve, which does not close completely, allows backward blood flow (regurgitation), creating a swishing or gurgling sound in the heart.
