"The groundwork of all happiness is health." - Leigh Hunt

What happens in our body after we sleep?

Hi my name is Abhilasa, I'm 9 years old and I'm from Melbourne and my query is what happens in our body after we sleep? Thanks – Abhilasa, 9, Melbourne.

Most of us consider sleep as a lightweight switch. That is, we go to bed, close our eyes, and our body “switches off.” Then, after we open our eyes and get up within the morning, we're “switching on” for the day.

But this just isn't true. At night after we sleep, some changes occur in our body.

The most interesting a part of our body that changes during sleep is our brain. We know this because people have been measuring how energetic our brains are during sleep because the Nineteen Fifties. They do that by placing small round pieces of metal (called electrodes) attached to wires near our head and eyes. These electrodes have shown that our bodies don't “switch off” after we sleep. There are literally many things our brain and eyes are doing.

Electrodes measure the waves generated by our brain. When we're awake, they've many waves, but they're really short. So numerous small waves means numerous activity in our brain. Also, after we are awake, our eyes are moving around and looking out at things – left and right, up and down, and all over the place.

When we close our eyes to sleep, we start to chill out and fall right into a very light sleep, generally known as “stage one” sleep. Our eyes move left and right, backwards and forwards, very slowly, repeatedly and really easily. This is named “slow rolling eye movement” – and it's something we will't do after we're awake. During first-stage sleep, our brain begins to supply barely larger waves, and fewer of them.

Next is “stage two sleep,” which is barely deeper sleep than stage one sleep. There just isn't much special about what our eyes are doing, but there's a special wave that our brain creates called the “sleep spindle”. It's a bit just like the brain waves seen in stage one sleep, but shorter, sharper and brighter.

The next stages of sleep are deeper, and are called stages three and 4 sleep. These stages are really deep, and really hard to get up from. The brain waves get really big – just like the ones you've seen on the beach.

Finally, one of the vital interesting stages of sleep is named “REM sleep.” REM stands for Rapid Eye Movement – so it means our eyes move in all places during sleep – similar to after we're awake. And our brain waves are just like after we get up. But it's during REM sleep that we dream.

Our brain goes through different stages of sleep – one, two, three, 4 after which back to REM sleep. We go up and down these stages all night long, until we get up within the morning.