Video Transcript
The cardiac cycle has two distinct
phases, systole and diastole. Complete the statement: The systole
phase occurs when the ventricles something and close the atrioventricular
valves.
First, let’s remind ourselves where
everything is located inside the heart. The atria are the two chambers at
the top of the heart, and the ventricles are the two chambers at the bottom of the
heart. The valves located in the pulmonary
artery and the aorta are known as the pulmonary valve and the aortic valve,
respectively, while the atrioventricular valves are found between the atria and the
ventricles. Just before systole, during the end
of the diastole phase of the cardiac cycle, the ventricles are relaxed and the
atrioventricular valves are open, meaning the ventricles fill with the blood that
enters the heart through the veins. Once the ventricles have fully
filled, they contract, forcing blood up and out of the heart through the
arteries.
The pressure in the ventricles is
now higher than the pressure in the atria. So, the atrioventricular valves
close. This is the systole phase of the
cardiac cycle. Now, we can answer the
question. The completed statement would be
“The systole phase occurs when the ventricles contract and close the
atrioventricular valves.”
