How Does the Human Heart Work?
Your heart beats 100,000 times a day without rest. Learn how its four chambers, valves, electrical system and double circulation keep you alive — plus what heart rate and blood pressure mean.
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Your heart beats 100,000 times a day without rest. Learn how its four chambers, valves, electrical system and double circulation keep you alive — plus what heart rate and blood pressure mean.
Vaccines train your immune system to recognize and fight diseases before you encounter them. Learn how they work and why they matter for public health.
Around 100,000 times per day at a typical resting rate — roughly 35 million beats per year. Over an average lifetime, that adds up to about 2.5 to 3 billion heartbeats.
Licensed vaccines cannot cause the disease they protect against. They contain weakened or inactivated germs, or only fragments of a germ — none of which can cause full infection. Mild effects like a sore arm or brief fever are signs your immune system is responding, not signs of infection.