Chapter 9

Your muscles are literally walking themselves into motion. Every time you move,

tiny proteins called myosin heads are grabbing onto actin filaments and pulling, like a microscopic

game of tug-of-war. This is the "molecular walk" that causes contraction. What’s wild is that

your heart is a muscle that runs on its own program. It has special pacemaker cells that generate

their own electricity, telling the heart muscle when to perform its molecular walk. This is why a heart

can beat even outside the body. So, from lifting a bag to your heart beating

right now, it’s all powered by tiny proteins taking a walk.