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The Cardiac Cycle (Quiz 2)

What purpose do the atrial and ventricular valves serve in the cardiac cycle? The heart provides force to drive blood through the circulatory system. The force is provided by contractions of the muscular walls of the ventricle which force blood out into the arteries. The cardiac valves control the direction of the flow. Think of a chamber of the heart as being like a tube of toothpaste with an opening at each end. If the tube is squeezed then paste will come out both ends. Only if one end is closed off will the flow be in a single direction. The chambers of the heart each have two opening so that blood can both enter and leave. The valves on each of these openings prevent back flow. A valve will open if pressure is applied from one side only. If pressure is applied from the other side then the valve is pushed shut. As a result blood can only flow in one direction.

View the animation below, then complete the quiz to test your knowledge of the concept.

1Ventricular systole causes...
A)blood to flow into the ventricles.
B)blood to flow out of the atria.
C)the atrioventricular valves to close, and then the semilunar valves to open.
D)the semilunar valves to close, and then the atrioventricular valves to open.
E)pressure to become greater in the aorta and pulmonary trunk than in the ventricles.

2When the pressure in the ventricles becomes lower than the pressure in the atria...
A)the ventricles contract.
B)blood flows into the pulmonary trunk.
C)blood flows into the aorta.
D)the atrioventricular valves open.
E)the semilunar valves open.

3The steps of the cardiac cycle in sequence are...
A)isovolumic contraction, isovolumic relaxation, ejection, passive ventricular filling, active ventricular filling.
B)isovolumic relaxation, isovolumic contraction, ejection, passive ventricular filling, active ventricular filling.
C)isovolumic contraction, ejection, isovolumic relaxation, passive ventricular filling, active ventricular filling.
D)isovolumic contraction, ejection, isovolumic relaxation, active ventricular filling, passive ventricular filling.
E)ejection, isovolumic relaxation, passive ventricular filling, isovolumic contraction, active ventricular filling.

4The beginning of ventricular systole is when blood flowing back toward the relaxed ventricles causes the semilunar valves to close.

5The atria never need to contract due to passive ventricular filling.

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