Question

What would be the heart rate of a person if the cardiac output is 5 L, blood volume in the ventricles at the end of diastole is 100 mL and at the end of ventricular systole is 50 mL ?

• A. 100 beats per minute
• B. 125 beats per minute
• C. 50 beats per minute
• D. 75 beats per minute

Answer 1

Answer: (A)

100 beats per minute

Answer 2

Cardiac output = stroke volume $\times$ Heart rate
$\Rightarrow$ Cardiac output = 5L or 5000 ml
$\Rightarrow$ Blood volume in ventricles at the end of diastole = 100 ml
$\Rightarrow$ Blood volume in ventricles at the end of systole = 50 ml
Stroke volume = 100 - 50
= 50 ml.
So,
5000 ml = 50 ml $\times$ Heart rate
So, Heart rate = 100 beats per minute.