When the lining of blood vessels isn't working right and makes less of a substance that keeps vessels open, it can raise blood pressure — even if the heart's pumping and blood amount stay the same.

In healthy people, a substance in blood vessels called nitric oxide helps keep blood pressure and vessel tightness in check. When scientists blocked this substance, blood vessels tightened up and blood pressure went up, showing how important it is for keeping things normal.

When you do aerobic exercise like running or cycling, it pushes blood through your vessels in a way that helps your blood vessels make a substance called nitric oxide. This substance helps your blood vessels relax and widen, which lowers your blood pressure.

As people get older, their bodies make less of a helpful molecule called nitric oxide, which makes it harder for blood vessels to work properly — and this can cause problems in the heart, brain, reproductive organs, and muscles.

A molecule called nitric oxide helps your blood vessels relax, your heart pump better, and your cells make energy properly — when this system goes wrong, it can lead to high blood pressure and heart problems.

As people get older, their blood vessels have a harder time relaxing because they produce less of a helpful chemical called nitric oxide, which makes it tougher for blood to flow freely — this is one reason why older adults are more likely to have heart and blood vessel problems.