Your Heart: A Self-Powered Blood Pump

Your heart is literally a self-powered electrical machine that beats without your brain even telling it

to. Inside your chest, you have a natural pacemaker called the SA node that

generates its own electricity to squeeze four muscular chambers in perfect rhythm. This pump is a beast,

pushing blood through a massive highway of arteries and veins to deliver oxygen while hauling

away trash like carbon dioxide. It even uses high-pressure valves that snap shut to stop blood

from flowing backward. It is the hardest working muscle you own, cycling your entire

blood volume every single minute just to keep you alive.