What prevents blood from flowing back into the atria when the ventricles contract?

• Pulmonary and aortic valves

• Sinoatrial node

• Atrioventricular node

• Tricuspid and mitral valves

When blood leaves this chamber of the heart, it heads out to the body.

• Left atrium

• Right atrium

• Left ventricle

• Right ventricle

One of the body's largest blood vessels that transports blood from the body region below the diaphragm to the heart is the __.

• Superior vena cava

• Inferior vena cava

• Aorta

• Pulmonary veins

When this chamber contracts, it pushes blood through the tricuspid valve.

• 6

• 7

• 8

• 9

This structure initiates the action potential that causes the heart to beat

• Inferior vena cava

• Atrioventricular node (AV node)

• Superior vena cava

• Sinoatrial node (SA node)

When blood leaves this chamber of the heart, it heads to the lungs.

• 6

• 7

• 8

• 9

Which best explains why capillary walls are so thin?

• Because they do not need to pump blood

• Because they are found only in the smallest organs and tissues

• Because they maximize diffusion of nutrients

• Because blood only travels through them slowly

Blood traveling through the systemic circuit goes through the _____ side of the heart and out to the body.

• Right

• Left

Which of the following is FALSE about pacemaker cells?

• They allow the heart to beat on its own

• They create their own electrical impulses

• They are part of the sinoatrial node and the atrioventricular node

• They require depolarizing stimulation from the brain

Which arteries directly supply the myocardium with blood?

• Pulmonary

• Coronary

• Aortic

• Brachial