Body Fluids and Circulation Question 52
52. 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) 50 beats per minute
(b) 75 beats per minute
(c) 100 beats per minute
(d) 125 beats per minute
Show Answer
Answer : c
Hints & Solutions
(c) Cardiac output is the product of the heart rate (HR), or the number of heart beats per minute (bpm), and the stroke volume (SV), which is the volume of blood pumped from the ventricle per beat; thus, Cardiac output $=$ stroke volume $\times$ Heart rate As per the given information, Cardiac output $=5 L$ or $5000 ml$ Blood volume in ventricles at the end of diastole $=100 ml$ Blood volume in ventricles at the end of systole $=50 ml$ $\therefore \quad$ Stroke volume $=100-50$ $ =50 ml \text{. } $ So, $5000 ml=50 ml \times$ Heart rate So, Heart rate $=100$ beats per minute.
