With age, the size of the heart typically ___ and the resting heart rate ___

Correct Answer: D

Rationale: With age, the heart size increases (D) due to hypertrophy from workload, and resting heart rate decreases due to reduced autonomic responsiveness and fitness.

Correct Answer: A

Rationale: Parasympathetic (vagal) stimulation slows the SA node (A), reducing heart rate (bradycardia). B, C, and D are sympathetic effects.

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: Venous blood in the right atrium has ~75% O₂ saturation (C, SvO₂) after systemic use (~25% extracted). A, B, and D underestimate normal values.

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.