The human brain constitutes about 2 percent of body weight. Which set of figures correctly describes its share of resting cardiac output and oxygen consumption?

• A 5 percent of cardiac output and 5 percent of oxygen consumption
• B 10 percent of cardiac output and 10 percent of oxygen consumption
• C 15 percent of cardiac output and 20 percent of oxygen consumption ✓
• D 25 percent of cardiac output and 35 percent of oxygen consumption

Explanation

At rest the brain receives about 750 mL/min of blood, roughly 15 percent of cardiac output, yet consumes about 3.5 mL of oxygen per 100 g per minute, close to 20 percent of total body oxygen use. This mismatch between weight and demand reflects its almost entirely oxidative metabolism with essentially no anaerobic reserve, which explains the extreme vulnerability of neurons to even brief hypoperfusion. The other figures substantially understate or overstate both values.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.