What Does Your Body Do When You Sleep?

Sleep is essential for good health. We need sleep to survive – just as we need food and water. Therefore, it is not surprising that we spend a third of our lives in a reliable source of sleep.

When you fall asleep, your body undergoes a series of changes that enable the rest needed for your overall health. Sleep allows the brain and body to slow down and engage in the recovery process, promoting better physical and mental functioning for the next day and longer.

Many biological processes take place during sleep:

  • The brain stores new knowledge and gets rid of toxic waste.
  • Nerve cells communicate and regenerate, supporting the healthy functioning of the brain.
  • The body repairs cells restore energy, and releases such as hormones and proteins.

These processes are important for our overall health. Without them, our bodies would not be able to function properly.

Let’s take a look at why we sleep, and what happens if we don’t get enough.

Table of Contents

Why do we sleep?

Not much is known about the purpose of sleep. However, it is widely accepted that there is not a single explanation for why we need sleep. It is necessary for many biological reasons.

In the next section Read more about what does your body do when you sleep?


What happens to your body during sleep?

Significant changes occur during sleep in almost every part of the body. Upon falling asleep, thousands of neurons in the brain switch from waking to sleeping, sending signals throughout the body.

While the biological role of sleep is still not fully understood, research has shown that it strengthens the cardiovascular and immune systems and helps regulate metabolism. What happens during sleep can be seen in significant changes in major physiological processes.


Breathing slows down during non-REM sleep and respiration reaches its lowest rate during the third stage of deep sleep. Breathing increases during REM sleep and may become irregular.

Heart rate

Like breathing, the heartbeat begins to slow down during stage 1 and reaches its slowest speed during stage 3. On the other hand, during REM sleep, the pulse wakes up at almost the same speed as waking up.

Muscle tone

During each phase of non-REM sleep the muscles relax slowly and the body’s total energy expenditure decreases5. During the REM phase, most of the muscles become paralyzed in a condition called atonia. This prevents the feet and hands from flapping in response to the dream material. The respiratory and eye muscles remain active, however, and the trembling of the eyes behind the closed eyelids is an inspiration called rapid eye dynamic sleep.

Brain activity

When measured during sleep, brain waves show a clear pattern associated with each sleep phase. In the early parts of non-REM sleep, brain waves are significantly slower; However, in Stage 2 and Stage 3, there are numerous rapid bursts of brain activity.

In REM sleep, brain activity becomes faster, showing different types of brain waves. REM sleep is known to be the phase associated with the most vivid dreaming due to increased brain activity.

REM sleep is thought to enable complex cognitive abilities, including memory aggregation, but non-REM sleep, even with a decrease in brain activity, is thought to play a role in facilitating proper brain function when awake.


REM Dreaming during sleep is most prevalent and intense, but it can occur during any phase of sleep 7. That said, dreams occurring during non-REM and REM sleep show different patterns 8 REM dreams are often more imaginative, immersive or bizarre.

Hormone levels

Sleep and the body’s internal clock, or circadian rhythm, play an important role in regulating the production of numerous hormones, including 9:

  • Melatonin, which helps promote sleep
  • Growth hormone, which supports bone and muscle growth as well as metabolism
  • Cortisol, which is part of the body’s stress response system
  • Leptin and ghrelin, which help control appetite

Hormone levels fluctuate during different stages of sleep and sleep quality can also affect daytime hormone production.

How much sleep do you need?

The advised amount of sleep depends on your age. It also varies from person to person, but the CDCT indicates the following period depending on the reliable source age:

  • 3 months from birth: 14 to 17 hours
  • 4 to 12 months: 12 to 16 hours per 24 hours including sleep
  • 1 to 2 years: 11 to 14 hours per 24 hours including sleep
  • 3 to 5 years: 10 to 13 hours per 24 hours including sleep
  • 6 to 12 years: 9 to 12 hours
  • 13 to 18 years: 8 to 10 hours
  • 18 to 60 years: 7 to 8 hours
  • 61 to 64 years: 7 to 9 hours
  • 65 years and older: 7 to 8 hours

Does sleeping help you heal when sick?

Sleep gives your body time to repair itself, which you need when you’re sick. When you get sleepy, it forces you to slow down and give your body the time it needs to heal. There are also certain immune processes that take place while you sleep that can bolster your body’s ability to fight off an illness.

What happens if you don't get enough sleep?

Without sufficient sleep, your body has difficulty functioning properly. Sleep deprivation is associated with chronic health problems that affect the heart, kidneys, blood, brain and mental health.

Lack of sleep is also associated with an increased risk of injury for both adults and children. For example, driver drowsiness can also contribute to serious car accidents and deaths. In adults; it is associated with an increased risk of poor sleep and bone loss.

Specific consequences of sleep deprivation may include:

  • Mood swings
  • Anxiety, frustration
  • Poor memory
  • Poor attention and concentration
  • Fatigue
  • Weakened immune system
  • Weight gain
  • High blood pressure
  • Insulin resistance
  • Chronic diseases and heart disease
  • The risk of early death increases

Frequently Asked question

Does your body turn off when you sleep?

Does your body just shut down? Not at all! You actually go through five stages during sleep, and your brain guides your body along the way, telling it how to sleep. In the first stage, your muscles relax, your body temperature gets a bit cooler, and your heart beats a bit slower.

What does your body do when u sleep?

Many biological processes happen during sleep: The brain stores new information and gets rid of toxic waste. Nerve cells communicate and reorganize, which supports healthy brain function. The body repairs cells, restores energy, and releases molecules like hormones and proteins.

Can you move your body when you are asleep?

Your muscles paralyse while asleep, you cycle through periods of non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM). It’s during REM sleep that we have the most vivid dreams. During this stage, your muscles are temporarily paralysed, meaning you can’t move.

Does your body heal faster when you sleep?

A good night’s sleep can improve your mood, help you stay alert and boost your memory. Now data show that getting enough Z’s might also get your cuts to heal more promptly. In fact, sleep was more important than good nutrition in speeding wound healing. This wasn’t what scientists had expected to see.



Sleep keeps us healthy and works well. It allows your body and mind to be repaired, restored and rejuvenated.

If you do not get enough sleep, you may experience side effects such as poor memory and focus, weakened immune system and mood swings.

Most adults need 7 to 8 hours of sleep every night. If you have trouble sleeping, talk to your doctor or sleep specialist. They can resolve the underlying cause and help improve the quality of your sleep.

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