Ventricular muscle receives impulses directly from the:

Correct Answer: A

Rationale: The Purkinje system (A) directly activates ventricular muscle. Bundle of His (B) and branches (C) precede, AV node (D) delays.

Correct Answer: C

Rationale: The medulla oblongata (C) houses the cardiovascular center, regulating heart rate via autonomic nerves. Midbrain (A), cerebrum (B), and cerebellum (D) have other roles.

Correct Answer: B

Rationale: Arterioles (B) offer the greatest resistance due to their small diameter and muscle control (Poiseuille’s law).

Correct Answer: A

Rationale: The pericardial cavity (A) between the visceral and parietal pericardium contains fluid to reduce friction. Other options are heart layers.

Correct Answer: C

Rationale: Stroke volume (C) is the blood volume per beat (~70 ml). Cardiac output (A) is per minute, heart rate (B) is beats, afterload (D) is resistance.