Contraction of skeletal muscles will ___ venous return, thus ___ stroke volume.

Correct Answer: C

Rationale: Skeletal muscle contraction (muscle pump) compresses veins, increasing venous return (C), which increases preload and stroke volume per Frank-Starling’s law. A, B, D mismatch effects.

Correct Answer: C

Rationale: ANH (C) decreases blood volume and BP by promoting sodium/water loss and vasodilation. ADH and aldosterone (A, B, D) increase volume.

Correct Answer: A

Rationale: Jugular veins (A) drain deoxygenated blood from the brain, head, and neck. Subclavian veins (B) drain arms, carotid (C) and brachiocephalic (D) are arteries.

Correct Answer: A

Rationale: The SA node (A) is the heart’s pacemaker, generating impulses at 60-100 bpm. AV node (B) delays, Bundle of His (C) conducts, and Purkinje fibers (D) spread the signal.

Correct Answer: C

Rationale: Capillaries (C) consist of a single endothelial layer for exchange. Arteries (A) and veins (B) have multiple layers (tunicae), and lymphatics (D) have thin walls but valves.