Grizzly bears have 50 percent body fat. They spend nearly half of the year sleeping. If people lived like that, they
would quickly develop health problems that would lead to heart attacks. Cardiologists hope that understanding
more about how bears' hearts function will help humans avoid heart disease, the leading cause of death in the
United States. Researchers have learned that two of the four chambers in a bear's heart shut down during
hibernation. Scans show blood pooling in the bear's heart during this time, which would block blood flow and
cause heart attacks in humans. However, bears' hearts stiffen during hibernation. The stiffened heart maintains
its shape and allows blood to continue flowing.
Do It!
Bears' hearts are
A inefficient
B collapsible
C vulnerable
D specialized