3. Heart again: At rest, the human systolic blood pressure is 120 mmHg a) Conver

Question

3. Heart again: At rest, the human systolic blood pressure is 120 mmHg a) Convert this pressure to SI unit: Pa. b) For an adult, a typical stroke volume is 80 ml, .e. the volume of blood pumped by the left ventricle through aorta in every heartbeat under the Systolic blood pressure. Assuming a resting heart rate of 75/min. Please calculate the amount of work done by the left ventricle in a day If the energy efficiency of heart is 20%, calculate the total energy consumed by the left ventricle in a day. Compare it to the Basal Metabolic Rate (BMR) of 1500 kCal/day c) d) Hints: i.Make sure your units are all in SI units. ii. Work done for flow: work-pressure × volume

Explanation / Answer

A)

1mmHg = 133.3 Pa

so,

120mmHg = 16000Pa = 16kPa.

B)

Total blood flow in a min = 75*80ml = 6 l=0.006m3.

total work done in a min = 0.006*16000 = 96J

total work done in a day = 96*60*24 = 138240J

C)

Total energy intake of left ventricle = 691200J

1500kCal = 6276000J, So the BMR is about 9 time more than the energy intake of the left ventricle.

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