Question Video: Describing the Systole Phase of the Cardiac Cycle | Nagwa Question Video: Describing the Systole Phase of the Cardiac Cycle | Nagwa

Question Video: Describing the Systole Phase of the Cardiac Cycle Biology • Second Year of Secondary School

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The cardiac cycle has two distinct phases, systole and diastole. Complete the statement: The systole phase occurs when the ventricles _ and close the atrioventricular valves.

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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.”

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