According to the passage, what happens to the heart during deep sleep?

It is tempting to think of sleep as time when nothing happens, time that could be better spent studying or scrolling through a phone. The body sees it differently. While you sleep, it is busy supporting the brain and repairing and maintaining the rest of you. In children and teenagers, sleep also supports growth.

Even the heart gets a rest. As you fall into deep sleep, your blood pressure and heart rate fall, and the heart does not have to work as hard as it does during the day. As you wake, they rise again to their usual level.

How you feel and how well you do during the day depends partly on what happens at night. Too little sleep, night after night, affects how well you think, learn, react and get along with other people. Over time, it can also raise the risk of long-term health problems, such as high blood pressure and heart disease.

So how much is enough? Experts recommend that adults sleep between seven and nine hours a night, and children and teenagers need more, depending on their age. That makes the student who stays up past midnight before every test an interesting case: they may be trading exactly the sleep that helps them think clearly for a few more hours of tired revision.