Conduction velocity is least in:

Correct Answer: A

Rationale: The AV node (A) has the slowest conduction (~0.05 m/s) to delay the signal. SA node (B) initiates, Purkinje (C, ~4 m/s) and Bundle of His (D, ~1 m/s) are faster.

Correct Answer: C

Rationale: The pulmonary semilunar valve (C) prevents backflow from the pulmonary artery into the right ventricle. Tricuspid (A) guards atrium-to-ventricle, bicuspid (B) is left-sided, and aortic (D) is systemic.

Correct Answer: C

Rationale: Increased stroke volume occurs with increased preload (more filling), decreased afterload (less resistance), and increased contractility (stronger contraction, C). Other combinations counteract.

Correct Answer: B

Rationale: The left ventricle pumps blood through the aortic semilunar valve (B) into the aorta during systole. Mitral (A) is inflow, pulmonary (C) is right-sided, tricuspid (D) is right AV.

Correct Answer: C

Rationale: The myocardium (C) is the muscular layer responsible for contraction. Endocardium (A) is inner, epicardium (B) is outer, pericardium (D) is the sac.