3. (a) Assume that the heart ventricle may be approximated by a sphere. If the r

Question

3. (a) Assume that the heart ventricle may be approximated by a sphere. If the radius of the ventricle doubles, what should be the increase in the value of the tension in the cardiac muscle to maintain the same pressure difference across the wall? What would be the increase in the force on the membrane wall? (b) The cardiac flow rate for an adult at rest is 9.7 x 105 m/s. The pressure drop from the arterial to the venous systems is 1.17 x 101 Pa. Calculate the power expended by the heart. 10 Marks

Explanation / Answer

a] Here the radius doubles, volume becomes 8 times, Pressure is same. In order to analyse forces , When we cut into a hemishperical shell, pressure*piR^2 = surface tension *2piR

Tension will become double

b] power exerted = rate of work done = d(PV)/dt = P*dV/dt = 1.17e4*9.7e-5 = 1.1349 W

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