Key Determinants of Blood Pressure

Steps:

• Blood pressure (BP) is calculated as cardiac output (CO) × total peripheral resistance (TPR).
• Factor 1 affects TPR: narrower vessel diameter increases resistance via Poiseuille's law (resistance ∝ 1/radius⁴).
• Factor 2 affects CO: higher systolic pressure in ventricles boosts stroke volume and arterial BP.
• Factor 3 affects CO: greater venous return increases preload, enhancing stroke volume per Frank-Starling mechanism.

Why A is correct:

• BP formula (BP = CO × TPR) shows all three factors influence either CO (factors 2 and 3) or TPR (factor 1).

Why the others are wrong:

• B excludes factor 3, but venous return directly modulates CO and BP.
• C excludes factor 2, but ventricular systolic pressure drives arterial pressure.
• D excludes factor 1, but vessel diameter is central to TPR regulation.

Final answer: A