13.3

What is the first event of the cardiac cycle as described in the learning material?

• The ventricles contract

• The atria relax

• The entire heart relaxes

• The atria contract

During the cardiac cycle, what happens when the ventricles contract?

• The atria contract

• The entire heart relaxes

• The atria relax

• The ventricles relax

What occurs immediately after the ventricular systole in the cardiac cycle?

• The atria contract

• The ventricles relax

• The entire heart relaxes

• The atria relax

What percentage of blood flows passively from the atria into the ventricles before the atria contract during the cardiac cycle?

• 50%

• 70%

• 80%

• 60%

During the cardiac cycle, what happens when the atria fill?

• The pressure in the ventricles becomes greater than in the atria, closing the AV valves.

• The AV valves close, preventing blood from entering the ventricles.

• The pressure in the atria is greater than in the ventricles, forcing the AV valves open.

• The ventricles contract, pushing blood back into the atria.

What causes the pressure within the heart chambers to rise and fall during the cardiac cycle?

• The contraction and relaxation of the ventricles only.

• The contraction and relaxation of the atria only.

• The contraction and relaxation of both atria and ventricles.

• The opening and closing of the AV valves.

What happens to the AV valves when the ventricles contract and the pressure inside them increases?

• The AV valves open

• The AV valves close

• The AV valves disappear

• The AV valves expand

What role do the papillary muscles play during the contraction of the ventricles?

• They relax the ventricles

• They open the AV valves

• They contract and pull on chordae tendineae

• They increase the pressure in the ventricles

What causes the heart sounds in humans?

• Blood flow through the heart

• Vibrations in heart tissues as valves close

• Movement of blood vessels

• Electrical impulses in the heart

What occurs during the first heart sound, also known as "lubb"?

• Ventricles relax and aortic and pulmonary valves close

• Ventricles contract and AV valves open

• Ventricles contract and AV valves close

• Aortic and pulmonary valves open