The Functions & Mechanisms of Sleep

If you’re like us, you may be curious to find out more about the function of sleep and why it’s so important. After all, we spend a third of our life sleeping so we can recharge and function daily. We’re delving into the stages of sleep and why they all have a

What actually happens when we sleep?

There are four stages of sleep divided into two categories. The first three stages fall into the category of non-REM (rapid eye movement) sleep. The fourth stage is REM sleep.

Stage 1

Stage 1 is where we begin to doze off before transitioning into stage 2. It is the lightest form of sleep and it is easier to be woken up during this stage.

Stage 2

Stage 2 involves further slowing of the brain and body’s activity. Just like stage 1, it’s an early stage of the sleep cycle- making it easier to wake up from.

Stage 3

During stage 3, your muscles and body relax even more, and brain waves show a clear pattern of slowed activity that is markedly different from waking brain activity. It is believed that deep sleep plays an important role in recuperation of the body as well as effective thinking and memory.

Stage 4

Stage 4 is the only stage of REM sleep. During this time, brain activity picks up significantly, and most of the body — except the eyes and breathing muscles — experience temporary paralysis. Although dreams can happen during any stage, the most intense dreaming takes place during REM sleep.

What is REM sleep?

The REM sleep stage is essential for the brain, enabling key functions like memory and learning. It’s normal to spend a larger percentage of time in REM sleep with most of it occurring in the second half of the night.

The structure of a person’s sleep stages and cycles is known as their sleep architecture. While deep sleep and REM sleep involve more profound changes in activity levels, experts believe that each stage plays a part in a healthy sleep architecture that generates quality sleep.

How does the body regulate sleep?

The body regulates sleep with two key drivers: sleep-wake homeostasis and the circadian alerting system.

  • Sleep-wake homeostasis. This technical term describes something most of us know implicitly from experience: the longer you’re awake, the more you feel a need to sleep. This is because of the homeostatic sleep drive the body’s self-regulating system in which pressure to sleep builds up based on how long you’ve been awake. This same drive causes you to sleep longer or more deeply after a period of insufficient sleep.
  • The circadian alerting system. Part of your body’s biological clock, circadian rhythms last roughly 24 hours and play a central role in numerous biological processes, including sleep. Light exposure is the biggest influence on circadian rhythms, encouraging wakefulness during the day and sleepiness at night.

These two factors directly affect how much your body feels a need for sleep, reflecting your biological clock, the time of day, your light exposure, and how long you’ve been awake.

In addition, a wide range of external factors can influence sleep-wake homeostasis and the circadian alerting system. For example, stress or hunger may disrupt your normal process for sleep regulation. Caffeine intake or exposure to light from electronic devices are other examples of how behavioral choices can alter the body’s underlying systems for managing sleep.

 

Resources:
https://www.nature.com/articles/npp2017294 
https://www.sleepfoundation.org/how-sleep-works