Blood pressure is defined as:

• A. The amount of blood pumped out in one minute
• B. The need for extra oxygen after strenuous exercise
• C. The pressure of circulating blood on the walls of blood vessels
• D. The rate of oxygen uptake by muscles

Answer: (C)

Blood pressure is the pressure of circulating blood on the walls of blood vessels. This describes the force blood exerts as the heart pumps and as it flows through the arteries, changing during the cardiac cycle with higher pressure when the heart contracts (systolic) and lower pressure when it relaxes (diastolic). It’s commonly measured in millimetres of mercury (mmHg). The other statements refer to different ideas: the amount of blood pumped per minute is cardiac output, not pressure; needing extra oxygen after hard activity relates to oxygen debt or ventilatory demand, not the pressure in vessels; and the rate of oxygen uptake by muscles is VO2, not blood pressure.