What Happens to Your Body (And Your Brain) While You Sleep?

Your muscles and organs slow down and switch modes at night to help get your body ready for the next day. . (Photo: Ollyy/Shutterstock)

If you're one of those people who doesn't put a premium on sleep, you might want to rethink that. Your body and brain are incredibly productive while you're off in dreamland. Take away that productive time and you could suffer the consequences.

When you sleep, your body and brain re-energize cells, clear waste and create memories. These processes are key for protecting your overall health and regulating specific functions that guide your mood, appetite, cognitive abilities and libido. Here's exactly what's happening in your body — and in your brain — while you sleep.

You cool off

Woman sleeping
Set an alarm to go off five hours after you fall asleep. Stay awake for at least 5 minutes and then go back to sleep to induce a REM cycle where dreams are more likely to happen. (Photo: ruigsantos/Shutterstock)

There's a reason that sleep experts suggest keeping the temp in your room cool at night. Cooler temps mimic the drop in temperature in your body that signals all systems that it's time for sleep. "Body temperature plays a complex role in falling asleep and awakening," said Dr. Joseph Krainin, founder of Singular Sleep, a virtual sleep clinic. According to Krainin, our body temps continue to fall during the night until they reach their lowest point in the early morning hours. After that, our temps start to rise again, signaling our body and brain that it's time to wake up.

Everything slows down (but that doesn't mean nothing is happening)

Your breathing and heart rate slow way down as you enter sleep mode; so do your muscles and organs. But that doesn't mean your body is off-duty; everything just switches modes. For instance, your intestines go from trying to clean out toxins to working to repair and prepare for a new day. Your body and brain use the time at night to make sure everything is in good order for the next day.

You build muscles and repair injuries

Woman lifting weights
Your body uses the down time at night to repair and build muscles from that tough workout you put in at the gym. (Photo: Lyashenko Egor/Shutterstock)

Whether you completed a grueling workout or gave yourself a paper cut at the office, your body uses the time when you're sleeping to repair muscles and other cells. Hormones, including growth hormones, cortisol, thyroid-stimulating hormones and insulin peak in the night hours. These hormones help to repair tissues and build muscles, and they're also essential in functions like appetite control, mood regulation and sex drive. If you've ever experienced ravenous hunger after a shoddy night's sleep, you know what it feels like when your body isn't given the opportunity to release those hormones.

You become paralyzed

Man sleeping
During REM sleep, your muscles become paralyzed to prevent you from punching and kicking your way out of your dreams. (Photo: pathdoc/Shutterstock)

It may sound crazy but it's true. When you're in your deepest phase of sleep — also known as REM or rapid eye movement sleep — all of your muscles except those that control breathing and eye movement become paralyzed, according to Science Daily. This is your body's way of preventing you from acting out those wacky dreams you may be having.

Your brain goes to work

Brain processes
When you sleep, your brain is hard at work processing and storing information (and learning) from the day's events. (Photo: Tatiana Shepeleva/Shutterstock)

You might think your brain is completely tuned out at night, but in reality, it's working as hard as it does when you are awake — it's just working on different stuff. In fact, " the brain waves seen in REM sleep resemble the brain waves of someone awake," said Dr. Robert Oexman, the director of the Sleep to Live Institute. Oexman explained that during sleep, we see an increase in cerebral spinal fluid that helps remove waste from the brain. During REM sleep, our brains are active in the areas that are associated with dreaming and the storage of memories. That's why many sleep experts think our dreams are the brain's way of processing information and storing useful tidbits for later use.

So, get some sleep!

Tired man
When you don't get enough sleep, your body and brain miss out on the chance to perform the processes they need to function properly. (Photo: pathdoc/Shutterstock)

When you don't get enough sleep, either because you think you're too busy to sleep or because you have a condition like sleep apnea that disrupts your sleep, your body and brain lose the opportunity to repair, replenish and restore their pieces and parts. And according to Krainin, that could leave you vulnerable to diseases like high blood pressure and Type 2 diabetes. Without the release of hormones and the regulation of brain processes, lack of sleep can also lead to issues such as depression, overeating, lack of interest in sex and learning disorders.

Still think you're too busy to sleep? I didn't think so.