How many clotting factors are necessary for clot formation?

Correct Answer: C

Rationale: There are 12 recognized clotting factors (I-XIII, missing VI) in the coagulation cascade, essential for normal clot formation, though not all are always active in every pathway.

Correct Answer: D

Rationale: Cardiac output (CO = HR × SV) is determined by all listed factors : heart rate (A), preload (B) affects stroke volume (SV), afterload (C) resists SV, and myocardial contractility (D) influences SV. All contribute to CO.

Correct Answer: C

Rationale: The pulmonary veins (C) carry oxygenated blood from the lungs to the left atrium. The aorta (A) carries blood from the left ventricle, pulmonary artery (B) from the right ventricle to lungs, and superior vena cava (D) to the right atrium.

Correct Answer: A

Rationale: The AV node delays the impulse (~0.1s) to allow atrial contraction to finish filling ventricles before ventricular systole (A). B occurs naturally, C is due to Purkinje fibers, and D is unrelated.

Correct Answer: C

Rationale: The cardioregulatory center in the medulla oblongata (C) controls heart rate via autonomic signals. The atrium (A) has the SA node, hypothalamus (B) regulates other functions, and carotid artery (D) has baroreceptors.