What Happens When You Sleep?

Sleep is a vital part of our normal routine. In fact, we spend approximately one-third of our time doing it. Good sleep and getting enough of it is essential for good health and to various brain functions such as how nerve cells communicate with each other. However, what exactly happens when you sleep?

Scientists used to think that human beings are mentally and physically inactive during sleep. But they now know that's not the case. Your brain and body do quite a lot of work all night long that's key for your health.

Here's everything you need to know about sleep, including how sleep works, along with the tips to help you get a good night's rest.

Sleep Cycle

Sleep isn't uniform. Instead, during a normal sleep period, your body goes through about four to five sleep cycles. Each cycle is composed of four individual sleep stages. The first one is the shortest, falling between 70 and 100 minutes, while later sleep cycles tend to range from 90-120 minutes.

What Are the Sleep Stages?

Generally, there are four sleep stages; three that form non-rapid eye movement (NREM) sleep and one for REM sleep. The breakdown of sleep into different cycles and stages is usually referred to as sleep architecture.

NREM Sleep Patterns

NREM sleep patterns are broken down into three different stages. The higher your stage the harder it is to wake up from your slumber.

Stage 1

This is essentially the "dozing off" stage, which represents the act of transitioning into sleep. It normally lasts for about one to five minutes.

During this stage, your body hasn't fully relaxed, but the brain and body activities start to slow down with periods of brief movements. You can easily wake someone up in this stage, but if there's no disturbance, a person can quickly move into stage 2.

Stage 2

In stage 2, your body and mind enter a more subdued state as you experience slowed breathing and heart rate, relaxed muscles, and also a drop in temperature. Your brain waves start showing a new pattern and rapid eye movement stops.

Stage 2 sleep lasts for about 25 minutes during the first cycle. Collectively, you'll typically spend about half your sleep time in the second sleep stage.

Stage 3

At stage 3, also referred to as deep sleep, your body is in recovery mode and it relaxes even further as your muscle tone, breathing rate, and pulse decrease. During this period, your brain activity has an identifiable pattern of delta waves.

The third sleep stage is crucial for restorative sleep, enhancing bodily recovery and growth. Plus, it may bolster your immune system and other vital bodily processes. During the early sleep cycles, you'll spend between 20 and 40 minutes in deep sleep. As the night unfolds, these stages become shorter and you'll spend more time in REM sleep instead.

REM Sleep Patterns

During REM sleep, brain activities shoot up, nearing levels experienced when you're awake. However, your body experiences atonia (temporary paralysis of your muscles save for the eyes and those that control breathing).

REM periods are believed to be crucial to cognitive functions like creativity, memory, and learning. They're known for the most vivid dreams due to the rapid uptick in brain activity. Although dreams can occur at any stage, they're less intense in the NREM periods.

Normally, people don't enter the REM sleep stage until they've been staying asleep for approximately 90 minutes. As you continue sleeping, REM stages get longer, especially during the second half of the night. In total, these stages make up about 25% of sleep in adults.

What Happens to Your Body and Brain During Sleep?

When you sleep, virtually every part of your body experiences a series of changes to give you the rest that's crucial to your overall health.

Body Temperature

Your body temperature decreases as you get drowsy before going to bed and is lowest roughly two hours before you get up. During REM sleep, your brain switches off your body thermometer. That's when warm and cool temperatures will affect your sleep. Generally, a cooler room will help you sleep better.


As you fall asleep in the non-REM sleep stage, you breathe more slowly and in a regular pattern. Breathing reaches its lowest rates during the deep sleep stage. Then, it gets faster and varies more as you enter the REM stage.

Heart Rate

Deep, non-REM sleep reduces your blood pressure and pulse, thus giving your blood vessels and heart time to rest and recover. As with breathing, your pulse ramps up during REM sleep to nearly the same high rates as when awake.

Brain Activity

When you start drifting into non-REM sleep at night, brain waves slow down considerably and your brain cells start firing in a steady and more rhythmic pattern. However, the brain cells fire rapidly and randomly as you enter stages 2 and 3. Brain activities accelerate in REM sleep, which is why this stage is mostly associated with vivid dreaming.

Hormone Symphony

Sleep and the circadian rhythm (the body's internal clock) play a pivotal role in regulating hormone production at night. Your body lowers some of your hormones while you're asleep and makes more of others.

For instance, cortisol, which is part of your body's stress response system goes down whereas the levels of growth hormone and melatonin go up. Generally, hormone levels change during different stages of sleep. Plus, the quality of your sleep can affect hormone production during the day.

What Happens When You Have Trouble Sleeping?

When you have trouble falling asleep, you may not get the benefits that come with quality sleep. The specific effects vary greatly depending on the type of sleep disorder or problem and Its cause. For example, disrupted sleeping from sleep apnea or restless leg syndrome can cause frequent awakenings, thus interrupting the normal sleep cycle.

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How Much Sleep Do We Need?

Various scientific researches make clear that quality sleep is essential irrespective of age. Sleep restores your body, powers your mind, and fortifies virtually every body system. However, how much sleep do you really need to get these restorative benefits?

The National Sleep Foundation guidelines recommend that healthy adults should sleep for about 7 to 9 hours each night. Teens, young children, and babies need even more sleep time to enhance growth and development. The elderly (people over 65) also require between 7 and 8 hours per night.

Note that, knowing these general recommendations is just the first step to getting a restful night. You also need to reflect on your individual needs depending on your typical sleep patterns, daily activities, and overall health. Some questions that can help you assess your sleep needs include;

  • Do you have coexisting health problems?
  • Are you productive, healthy, and contented with 7 hours of sleep?
  • Are you experiencing sleep disorders?
  • Do you work in a labor-intensive environment?

Sleep Debt: What Are Some of the Consequences of Sleep Deprivation?

Sleep deprivation refers to getting less sleep than the required amount. When you sleep for fewer hours per night than your body requires, you have a sleep debt. Its effects can be serious and far-reaching. This often occurs when you're helping an infant sleep at night or working during odd hours. 

Chronic sleep deprivation, for instance, can contribute to various health problems. Since sleep plays a vital role in the effective functioning of virtually all body systems, a persistent lack of it heightens the long-term risk of mental and physical health problems.

Your body becomes prone to various health issues such as;

  • Diabetes
  • Hormonal abnormalities
  • Cardiovascular diseases
  • Obesity

Acute sleep deprivation, on the other hand, raises the risk of accidents and unintentional errors. Sleep-deprived people often struggle in work and school settings. They're also likely to experience mood changes that can affect personal relationships.

Related content: Why do we sleep?

What If You Sleep Too Much?

Hypersomnia is a health condition caused by sleeping too much. If you're suffering from hypersomnia, you'll often experience excessive daytime sleepiness and you may find it difficult to stay awake and active when you need to. This condition is associated with alterations in sleep architecture like an increase in non-REM sleep and a reduction in deep sleep, which affects your overall sleep quality.

How to Get a Good Night's Sleep

Getting a good night's sleep is fundamental to your physical and mental health. Lack of it can negatively impact your immune system and decrease your mental acuity. Luckily, there are things that you can do to improve the quality and quantity of your sleep. In addition to reading mattress industry statistics for information about the most commonly used beds and the best ones for your sleep preference, you can:

Customize Your Bedroom Environment

Design your sleeping environment to be perfect for your relaxation. By ensuring your bedroom environment is inviting and fits your comfort preferences, you're likely to enjoy that restful sleep you crave.

Your pillows and mattress should provide plenty of support while your bedding should maintain a moderate temperature and help you feel cozy. To minimize potential sleep disturbances, ensure your room is as dark and quiet as possible.

Set Your Biological Clock

Keeping a consistent sleep schedule is one of the best ways of improving your sleep hygiene. Sleeping and waking up at the same time every night and morning will help you set your internal biological clock. Once you disrupt your sleep cycle, it might take longer to get back on track. So, always try to adhere to your regular sleep and wake times as much as possible even on weekends.

Related content: What is sleep hygiene?

Avoid Things that Can Interfere With Your Sleep

An effective way of addressing sleep deprivation is refraining from doing or using things that can negatively affect your sleep. They include;

Electronic Devices

Smartphones, computers, and TVs can keep your mind stimulated, so you may have a hard time falling asleep. Plus, these devices emit light that can interfere with your circadian rhythm. That's why you should avoid using them for an hour or more before going to bed.

Alcohol and Caffeine

Drinking alcohol, especially during the night can disrupt your sleep cycle, reducing sleep consistency and your overall sleep quality. Caffeine, on the other hand, makes you alert, so it's best to avoid it in the evening and at night a few hours before you go to bed.

Final Thoughts

As you can see, sleeping isn't a waste of time and there's no way you can get away without it. Aside from nutrition and physical activity, you need to pay close attention to sleep to stay healthy and productive. If you're having trouble sleeping, reach out to your sleep specialist who'll determine the underlying cause and provide medical advice on how to improve your sleep quality.

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