ANATOMY
CHEST AND CARDIOVASCULAR
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The left and rigth atria contract
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The left and right ventricles contract
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The atria fill with blood from the superior vena cava
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The tricuspid valve closes
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Detailed explanation-1: -Electrical charges spontaneously pulse from the SA node causing the two atria to contract in unison. The pulse reaches a second node, called the atrioventricular (AV) node, between the right atrium and right ventricle where it pauses for approximately 0.1 second before spreading to the walls of the ventricles.
Detailed explanation-2: -The sinus node generates an electrical stimulus regularly, 60 to 100 times per minute under normal conditions. The atria are then activated. The electrical stimulus travels down through the conduction pathways and causes the heart’s ventricles to contract and pump out blood.
Detailed explanation-3: -The conduction system of the heart. Normal excitation originates in the sinoatrial (SA) node, then propagates through both atria (internodal tracts shown as dashed lines).