Sleep cycles

Sleep Cycles
Now that you know the basics of how sleep works, we can explore how deep the rabbit hole really goes :o) What is quality sleep?
Well, first you may want to understand that the sleep stages explained above don't happen only once during sleep. They happen multiple times during sleep in what are called sleep cycles.
During a sleep cycle, we progress from stage 1 to stage 5 multiple times. It would seem really complicated to write out how this works, and because I want you to understand this and grasp this concept clearly, I've drawn it out for you! Aren’t I Great? Refer to the graph below, and then we'll go over it in detail.

http://images.plurk.com/4596312_3db88830997acfd29c7d3ebdf9c00c59.jpg

So what's happening here? Well, the typical way we travel through our sleep stages in sleep cycles is as follows:

1, 2, 3, 4, 3, 2, REM, 2, 3, 4, 3, 2 REM 2, 3, 4, 3, 2, REM, 2, 3, 4, 3, 2 REM……

On average, each one of these cycles takes about 60 — 100 minutes, varying from person to person.

As you study the graph carefully, you may notice a couple of other things happening

1. Notice how the first period of deep sleep is the longest. Notice how the stages of deep sleep get shorter and shorter, and eventually non existent towards the end of the night.

2. Notice how the first duration of REM sleep is very short; notice how these periods get longer towards the end.

The understanding you may get out of this is that sleep gradually gets lighter as the night progresses.
You may have also realized that we don't spend an equal amount of time in each stage of sleep. You're right, and this is where we'll answer the “What is Quality Sleep?” question.

Look at the chart below:

http://images.plurk.com/4596312_b56c8435fcdb768dd870b9a629723a60.jpg

How Important is Deep Sleep?

— It's been proven that when we're deprived of deep sleep, we experience our greatest day-time impairments, such as drowsiness, nausea, headaches, muscle
aches, and trouble concentrating.
— When we're deprived of sleep for any irregular amount of time, our body will sacrifice all other stages of sleep to regain “deep sleep”. It's believed this is why our body tries to gain as much deep sleep as possible in the first 3-4 hours of our sleep.
— Because deep sleep is the first stage of sleep the body tries to get the most of, it's the stage least likely to be missed. As you may recall from the previous graph, the periods of deep sleep were longest in the beginning.
— Our immune system also turns on during deep sleep to fight diseases. This is why we sleep more when we're ill.

How Important is REM Sleep?

Studies show that when we're deprived of REM sleep, we exhibit certain day-time difficulties as well, mainly trouble with concentrating, and sometimes drowsiness. However, because the body tries to recover deep sleep first as a result of sleep deprivation, we can assume that REM sleep isn't as important to restoring our physical functions. It's not clearly known what purpose REM sleep serves; however, scientists do have a theory that we absorb most of our daytime learnings during REM sleep. This would explain why babies spend so much time sleeping, 50% of that time in REM sleep.

So what is Quality Sleep?

As you may have already guessed, quality sleep consists of being able to sleep deeply. For our minds to easily slide into the deep stages of sleep, and stay there for the time needed. Easier said than done.
So I've got a question for you: What controls how long and how deep you sleep?