Power of a Human Heart

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Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Fay, J. & Sonwalkar, N. A Fluid Mechanics Hypercourse CD-ROM. Cambridge, MA, MIT Press, 1996. "Under normal conditions, the heart beats 75 times per minute, delivering about 5 liters per minute, but its flow can be five times greater under extreme conditions. The peak blood pressure in the heart is about one-sixth of an atmosphere, and the heart develops about two watts of mechanical power." 2 W
Koehler, Kenneth R. College Physics for Students of Biology and Chemistry. Cincinnati, OH: Raymond Walters College University of Cincinnati, 1996: Chapter 3, Fluids: Human Cardiovascular System. "For instance, we can compute the power output of the heart as the product of the pressure times the flow (volume per unit time). If you have six liters of blood and it circulates every minute, the flow rate is 100 cm3/s. If the pressure averages 133,000 dynes/cm2 (ignoring pulsatile flow), then the average power output is 13,300,000 ergs/s or 1.33 watts. This may not seem like much, but consider the amount of energy produced by your heart in a day (86,400 s). This is approximately 115,000 J, which is the energy the average (70 kg) person would have after falling from a 550 foot tall building!" 1.33 W
Malinski, Tadeusz. Chemistry of the Heart. Oakland University. "The mechanical power of the human heart is ~1.3 watts. It takes a much higher rate of energy turnover (~13 watts) to provide this mechanical power, since the mechanical efficiency of the heart is very low (less than 10%)" 1.3 W
Sadr, Farokh S. Heart Matters. "A normal heart in an average sized person will pump 4 to 5 liters of blood per minute. And the average heart will beat almost 4 million times per year [sic, they probably mean 40 million -- ed.]. It is estimated that the energy required to continuously pump blood at these rates is almost 5 watts of power per hour [sic, watts of power is fine, watts of power per hour is a non sequitur -- ed.]." 5 W
Klevickis, Cynthia. Energy and the Heart [doc]. Energy in Living Systems. Harrisonburg, VA: Department of Integrated Science and Technology James Madison University, 2003. "How much energy does the heart need? Use the following equations and numbers:
Mechanical Power = Pmax(C,O)
Chemical Power = Mechanical Power/nth
Systolic Pressure: 16 kN/m2
Cardiac Output: 107 × 10-6 m3/s
nth = 0.2
Answer:
Pmech = (16 kN/m2)(107 × 10-6 m3/s) = 1.71 (Nm)/s [W]
Pchem = 1.71 (Nm)/s = 8.6 (Nm)/s"
1.71 W

The human heart is a pump that is made of muscle tissue. It has four chambers: the right atrium and the left atrium, which are located at the top, and the right ventricle and left ventricle, which are located at the bottom. A special group of cells called the sinus node is located in the right atrium. The sinus node generates electrical stimuli that make the heart contract and pump out blood. Each contraction represents a heartbeat. When the heart contracts it is in a systolic phase and when it rests it is in a diastolic phase. It takes blood about a minute to circulate through the cardiovascular system and pump oxygenated blood throughout the body.

The power of the heart can be calculated by multiplying the pressure by the flow rate. An average person has six liters of blood that circulates every minute, making the flow rate 10-4 m3/s (cubic meters per second). The pressure of the heart is about 104 pascal, making the heart's power about one watt. This is the power of a typical human heart, but it's different for everyone.

The average heart beats about 75 times per minute, which is about five liters of blood per minute. Although this isn't much, it enables the heart to complete a tremendous amount of work in a person's lifetime. The human heart beats about 40 million times a year, which adds up to more than 2.5 billion times in a 70-year lifetime. This results in approximately 2 to 3 billion joules of work in a lifetime, which is a huge amount.

Irada Muslumova -- 2003


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