Did you know that, on average, human beings spend one-third of their life sleeping? Well, if you are reading this with red-rimmed eyes, after pulling an all-nighter, you might have a hard time wrapping your mind around that idea. 

However, sleeping might require little effort on your part (not if you have an insomniac brain), but the process of sleep is rather complicated. Sleep is such a fascinating physiological phenomenon that scientists are yet to unlock the true reason or the mechanics of sleep.

The six to eight hours you sleep, your body has to go through four different sleep cycle stages, release hormones, and restore memories, although you are hardly aware of any of them happening. Read on to find out what happens in your sleep and why you need it.

Why Is Sleep Important?

Have you ever felt groggy or cranky after having a poor night’s sleep? It’s because sleep controls your overall mental and physical wellbeing. When we sleep, our body gets a chance to rest and rejuvenate while our brain sorts out the day’s events and memories, just like a busy librarian working an extra shift. Just missing a few hours of sleep can affect your ability to concentrate on work and result in increased stress levels.  

Aside from a messed-up routine, you might also develop some health issues such as obesity, diabetes, heart complications, and other severe health conditions. Considering all these, you need to improve your sleep quality by adopting a better sleep routine, maintaining a healthy diet, or taking natural supplements. You can read more on the Resurge supplement to learn how it can improve your sleep quality.

Who Controls Your Sleep?

Ever wondered why we all humans sleep at night and stay awake during the day? That is because we have a biological clock built within our brain that responds to light. The system is called the circadian rhythm. After receiving signals from ambient light, it releases your sleep hormone, melatonin.

But when it is light, the circadian rhythm stops the melatonin, making you alert and awake. This is also the reason why we tend to sleep with the lights off. And there is another factor called sleep drive; it works just like hunger- you feel this all-consuming urge to sleep whenever you are tired.

This sleep drive or sleep homeostasis reminds you to sleep after certain hours of wakefulness. It also controls the intensity of your sleep. When you disrupt this system, you have trouble sleeping at night and being awake during the day.

What Happens When You Sleep?

Sleep might be a passive function for you- you just need to turn off the light, lie down and pull up the covers, and you are asleep. But a full night’s sleep involves four different stages, and you cycle through these stages four or five times.

These cycles can last for 90- 120 minutes. These stages can be broadly divided into two types- NREM (non-rapid eye movement) and REM (rapid eye movement) sleep.

NREM Phase

The first two stages are the NREM light sleep phase, where your consciousness turns to sleepy from being awake. Your heart rate slows down, muscle cramps, and body temperature falls. At stage three, your brain releases delta waves, low frequency but loud brain waves that help you suspend all external awareness.

The Delta stage is also the first stage of deep sleep; our body releases most of the growth hormone at this stage to help our body to rejuvenate. Delta sleep lasts for 20-40 minutes.

REM Phase

The last stage is where you dream. With different body chemicals partially paralyzing your body, your mind travels as you dream, but your body stays where it is, unmoving. The brain remains the most active during this phase, allowing you relief from the thoughts that lurk in your subconscious mind, in the form of dreams.

As you dream, your eyes might twitch behind the closed leads, a subconscious reflex from your dream. This stage can last for 10-60 minutes.

Brain Activity

Our brain produces different brain waves during each sleep cycle. Both REM and NREM sleep play essential roles in processing memories and activating cognitive abilities. While your brain activity slows down at the first stage, during the last part of your sleep, it perks up again.

At this sleep stage, you start to have vivid dreams about the day’s incidents. It is regarded as your brain’s way of making you face the unwanted situation without you having to confront them physically.

Breathing and Heart Rate

Your breathing and heart rate gradually slows down as you fall asleep. This process starts at the first stage of NREM sleep. At the third stage of NREM sleep, you experience the lowest heart rate. It perks up again as you enter REM sleep.

Hormone Levels

Our circadian rhythm also controls the production of certain hormones. Melatonin is released after the circadian rhythm receives light cues, which is our sleep hormone. As the light goes to dark at night, this hormone is released from your brain’s pineal gland, making you sleepy.

During sleep growth, the hormone is released from the pituitary gland, which helps muscle and bone growth. Our sleep controls the hormones responsible for our appetite, leptin, and ghrelin. Leptin is released when you sleep making you feel full. Our stress hormone cortisol is also coordinated with our sleep. When we sleep, our cortisol level drops; that is why it is hard to fall asleep when we are anxious.

Muscle Activity

In sleep, you have almost no energy expenditure. It allows your muscles to relax gradually in NREM sleep. NREM sleep is also the stage where blood flows to your muscle for tissue repair and growth.

During REM sleep, you enter a state of partial paralysis; it inhibits your muscle movement while you have a vivid dream. Although your respiration and eye movement continue, you can’t flail around your arms or legs in response to your dreams.  

How Long Can You Go On Without Sleep?

Sleep is as important as food for you to live. Being awake for 24 hours at a stretch can lead to drowsiness, vision impairment, impaired decision making, and so on. Lacking sleep for 36 hours can alter your bodily function- temperature, appetite, metabolism, and stress.

You will have a hard time keeping your eyes open if you stay awake for 48 hours. It can also impact your immune system, making you prone to sickness. Staying awake more than 72 hours can make you hallucinate, alter your visual and mental perception.

The Bottom Line

Even if you are convinced you can manage well by squeezing in a little sleep here and there, you are actually signing up for some long-term consequences. Think of it this way, if you were to work seven days a week, without any break, how would you feel? What would it mean for your productivity?

Similarly, your body can not fare well without adequate quality sleep. Chronic sleep deprivation can cause you to be forgetful, cognitively impaired, paranoid, and accident-prone. So get in sync with your circadian rhythm and get some shut-eye.


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