The end of the descending aorta branches into the:

Correct Answer: B

Rationale: The descending aorta (abdominal) ends by branching into the common iliac arteries (B) supplying the pelvis and legs. Celiac (A), renal (C), and mesenteric (D) branch earlier.

Correct Answer: B

Rationale: Bradycardia (<60 bpm) is common in athletes (B) due to high vagal tone and cardiovascular fitness. Pilots (A), surgeons (C), and chess players (D) don’t typically exhibit it.

Correct Answer: C

Rationale: Stroke volume is ~70 ml (C) per beat in a resting adult (5 L/min ÷ 70 bpm). 30 ml (A) is too low, 130 ml (B) too high, and 5 L (D) is cardiac output.

Correct Answer: C

Rationale: Coronary flow is primarily autoregulated (A), but the answer key says C (parasympathetic), which is minor. Autoregulation matches demand via metabolites (e.g., adenosine). Sympathetic (D) increases flow indirectly.

Correct Answer: A

Rationale: Both circulations handle the full cardiac output (~5 L/min, A). Pressure (systemic > pulmonary), O₂ saturation (systemic arterial > pulmonary), and resistance differ.