What is the role of the SA node in cardiac conduction?
It synchronizes ventricular contraction
It prevents backflow of blood
It delays impulses to allow ventricular filling
It initiates the action potential for heart contractions
The Correct Answer is D
A. It synchronizes ventricular contraction: Synchronization of ventricular contraction is primarily the function of the Purkinje fibers and the coordinated conduction through the AV node and bundle branches, not the SA node.
B. It prevents backflow of blood: Prevention of backflow is the role of heart valves, such as the mitral and aortic valves, rather than any conduction system component.
C. It delays impulses to allow ventricular filling: The AV node provides a delay to allow the ventricles to fill with blood, which is distinct from the SA node’s role.
D. It initiates the action potential for heart contractions: The sinoatrial (SA) node, located in the right atrium, generates electrical impulses that set the pace for heart rate. These impulses trigger atrial contraction and initiate the cardiac conduction cycle.
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Related Questions
Correct Answer is A
Explanation
A. Left atrium: The left atrium receives oxygenated blood from the pulmonary veins after it returns from the lungs. It then contracts to pass this blood into the left ventricle for systemic circulation.
B. Right atrium: The right atrium receives deoxygenated blood from the superior and inferior vena cava. It sends this blood to the right ventricle, which then pumps it to the lungs for oxygenation.
C. Left ventricle: The left ventricle receives oxygenated blood from the left atrium and pumps it through the aorta to the body. It does not directly receive blood from the lungs.
D. Right ventricle: The right ventricle receives deoxygenated blood from the right atrium and pumps it into the pulmonary artery to the lungs. It does not handle oxygenated blood from the lungs.
Correct Answer is B
Explanation
A. T cells: T cells are primarily involved in cell-mediated immunity. They help regulate immune responses and destroy infected or abnormal cells but do not directly produce antibodies.
B. B cells: B cells are responsible for humoral immunity and differentiate into plasma cells that secrete antibodies. These antibodies bind to specific antigens to neutralize or mark them for destruction by other immune cells.
C. Macrophages: Macrophages are phagocytic cells that engulf pathogens and present antigens to lymphocytes. They support the immune response but do not produce antibodies themselves.
D. Natural killer cells: Natural killer cells destroy infected or cancerous cells through cytotoxic activity. They are part of innate immunity and do not generate antibodies.
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