Pump the bottle as many times as your heart beats in one minute in the inactive mode. This can be timed quickly, or return to the data in the lesson, Heart Throbs. Note any difficulty the pumper might have had. Collect the water in the beakers and measure it. Record the measurement.
Repeat steps one and two.
Replace the screw, increase the size of the screw used, pump. Have students make inferences on what happens when the heart works twice as fast as usual. The concept of the stroke can then be displayed. A stroke is caused by a blood clot in an artery of the brain. Have students research the causes of arterial blockage and look for ways in which lifestyles influence such problems.