Summary

Bryson begins Chapter 7 by explaining the functions and parts of the heart, after noting it is not involved in emotions even though we talk about it as if it is. Hearts beat about 100,000 times a day and as many as 3.5 billion times in a lifetime, dispensing 1,680 gallons of blood a day. The heart weighs less than a pound and is divided into four chambers: two atria and two ventricles. The heart is two pumps: one that sends blood to the lungs and another that sends blood around the body. Maintaining blood pressure is not as simple as it may seem. Blood pressure is not a fixed figure and, for much of medical history, it was thought that high blood pressure was actually a good thing. It was not until Franklin Delano Roosevelt died of heart disease that medical science began...