7.13—Cardiac output, ventilation and control centres

Cardiac output is the volume pumped by a ventricle per minute: cardiac output = heart rate × stroke volume. It rises during exercise so working cells receive more oxygen and substrates.

Keep units consistent, convert cycle time into beats per minute, then rearrange the equation when heart rate or stroke volume is unknown.

If one cardiac cycle lasts 1.2 s, heart rate is 60 ÷ 1.2 = 50 bpm. With stroke volume 75 cm³, cardiac output is 3,750 cm³ min⁻¹ or 3.75 dm³ min⁻¹.

A higher heart rate does not always mean a higher cardiac output if stroke volume falls. Cardiac output is a volume per time, not the blood pressure itself.