What Happens to Your Brain and Body During Sleep? Tips For Improving Sleep Update 06/2024

The importance of sleep cannot be overstated. Sleep is as essential to our survival as food and water. Since we spend nearly a third of our lives sleeping, it’s understandable.

Sleep is a time when several biological activities take place:

  • New information is stored in the brain, and old knowledge is excreted.
  • The healthy functioning of the brain is supported by the communication and reorganization of nerve cells.
  • Cells are repaired, energy is restored, and chemicals such as hormones and proteins are released by the body.

Our general well-being depends on these processes. Our body wouldn’t work properly without them.

Examine the reasons for sleeping, as well as the consequences of not getting enough of it.

Why do we sleep?

There is still a great deal of mystery around sleep’s function. The fact that there isn’t just one reason for why humans must sleep is generally recognized. It’s probably essential for a wide range of biological factors.
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Scientists have discovered numerous ways that sleep benefits the body so far. The next section provides an overview of the most popular hypotheses and supporting evidence.

Energy conservation

Sleep is necessary for energy conservation, according to the hypothesis. In order to limit the amount of calories we consume, we can sleep, which lowers our metabolic rate for a period of time.

As our metabolic rate decreases during sleep, this theory is supported. Humans have been shown in studies to save 35% more energy per day when sleeping 8 hours a night than when awake the entire day.

It’s been proposed that sleep has a dual purpose: to conserve energy during periods of uncomfortable and inefficient foraging, such as day and night.

Cellular restoration

According to the restorative notion, sleep is essential for the body’s self-restoration.

Cells are able to repair and regenerate during sleep, according to the theory. It’s backed up by a slew of processes that take place during sleep, such as:

  • muscle repair
  • protein synthesis
  • tissue growth
  • hormone release

Brain function

According to the hypothesis of brain plasticity, sleep is necessary for proper brain function. Neurons, or nerve cells, are able to restructure as a result.

The glymphatic (waste removal) system in your brain cleans up the central nervous system as you sleep. It flushes out the toxins that accumulate in your brain over the day. When you wake up, your brain is ready to go.

By transforming short-term memories into long-term memories and deleting, or forgetting, unnecessary information, sleep appears to have a role in memory function.

Several parts of the brain’s functioning are affected by a lack of sleep

  • learning
  • memory
  • problem-solving skills
  • creativity
  • decision making
  • focus
  • concentration

Emotional well-being

Sleep, on the other hand, is essential for emotional well-being. Brain activity increases during sleep in areas that control emotional responses, promoting healthy brain function and emotional stability.

Sleep enhances activity in the brain’s limbic system, hippocampus, and neocortex.

  • amygdala
  • striatum
  • hippocampus
  • insula
  • medial prefrontal cortex

The amygdala is a part of the brain that regulates emotional responses. The fear response is controlled by this portion of the brain in the temporal lobe. When confronted with a perceived threat, such as a stressful circumstance, your body’s natural response is to fight or flee.

The amygdala can be more flexible in its responses when you receive enough sleep. The amygdala, on the other hand, is more inclined to overreact if you’re sleep deprived.

Sleep and mental well-being are linked, according to recent studies. Depression and other mental health concerns may be exacerbated by sleep disruptions, but so may sleep abnormalities be exacerbated by depression.

Weight maintenance

Sleep regulates hunger hormones, which in turn influences your weight. While ghrelin is known to induce hunger, leptin is known to make you feel full after eating.

To put it simply, when you’re sleeping, ghrelin levels drop because you’re utilizing less energy.

Lack of sleep, meanwhile, raises ghrelin and suppresses leptin. This imbalance causes you to be more hungry, which can lead to overeating and weight gain.

reveals that persistent sleep deprivation, even as few as five consecutive nights of poor sleep, may be related with increased risk of:

  • obesity
  • metabolic syndrome
  • type 2 diabetes

Proper insulin function

Insulin is a hormone that helps your cells use glucose, or sugar, for energy. Insulin resistance, on the other hand, means that your cells don’t respond to insulin effectively. This can lead to excessive blood glucose levels and, eventually, type 2 diabetes.

Insulin resistance may be prevented by enough sleep. As a result, your cells remain strong and can more readily absorb glucose.

As a result, the body is able to manage blood glucose levels more effectively during sleep.


Sleep is essential to maintaining a healthy immune system. A lack of sleep can impair the immune system, leaving you more vulnerable to infection.

Proteins called cytokines are produced by your body as you sleep to help fight infection and inflammation. Immune cells, such as antibodies, are also produced. These chemicals work in concert to keep people healthy by eliminating pathogenic microorganisms.
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Getting enough sleep is crucial when you’re sick or under a lot of pressure. An increase in immune cells and proteins is required by the body at these times.

Heart health

Scientists believe that sleep improves cardiovascular health, even though the particular mechanism is unknown. Heart disease and sleep deprivation are linked.

If you’re an average adult, the Centers for Disease Control and Prevention (CDC) recommends that you get seven hours of sleep per night. On a regular basis, not getting enough of that can lead to a wide variety of health issues, many of which can harm your heart health.

Risk factors for heart disease, such as sleep deprivation, include:

  • blood pressure is too high.
  • sympathetic nervous system activity is elevated.
  • elevated levels of inflammatory cytokines.
  • increased levels of cortisol
  • An increase in body mass.
  • Diabetes mellitus is characterized by insulin resistance.

How Does Sleep Change During the Night?

You go through four to five sleep cycles in a typical night’s sleep. During a typical sleep cycle, there are four distinct stages of sleep.

Rapid eye movement (REM) and non-REM sleep are further subdivided into four stages of sleep. The distinction between REM and non-REM stages of sleep necessitates the usage of these classifications.

Non-REM activity occurs in the first three stages of sleep. Stage 1 lasts only a few minutes, and it represents the moment when you begin to nod off and drift off to sleep. As you go off to sleep, your body and mind slow down to Stage 2. During the first two stages, it’s the easiest to be awakened.

Slowing down even further occurs during Stage 3, sometimes referred to as deep sleep. Meanwhile, brain activity slows and takes on a distinctive pattern of pulses, which may serve as a safeguard against unwelcome awakenings.

REM sleep is the fourth and final stage. While asleep, brain activity is at its highest level, which is why REM is associated with the most vivid dreams and nightmares. Our muscles are paralyzed while we are in REM sleep, which prevents us from acting out our dreams.

Between 70 and 120 minutes are required for each sleep cycle. Non-REM sleep is more prevalent in the first half of the night’s sleep cycles. Most REM sleep occurs in the second half of the night. Sleep architecture refers to the succession of sleep stages and cycles throughout a single sleep period.

What happens when you sleep?

As you sleep, your body goes through four stages. At various points during each of these periods of sleep, the cycle repeats again for a period of 70 to 120 minutes. There are four to five stages that reoccur over a seven to nine-hour period of sleep.

Non-rapid eye movement (non-REM) sleep and rapid eye movement (REM) sleep are the two key phases of sleep in this pattern. Three stages are non-REM sleep, and one stage is REM sleep, making up the four stages of sleep.

Non-REM sleep is defined by no eye movements, whereas REM sleep, which occurs during dreaming, is marked by frequent eye movements.

The following is a chart outlining the various stages of sleep.

Stage 1: Non-REM sleep

Stage 1 starts as soon as you begin to sleep. Your brain waves, heart rate, and eye movements slow down when your body enters light slumber.

About seven minutes into this phase, you’ll notice a noticeable change in your mood.

Stage 2: Non-REM sleep

This is a transitional state between a light sleep and a profound sleep.

Eye movements stop; the heart rate and muscles relax; and your body temperature drops. After a brief spike, your brain waves begin to calm down.

You spend the most time in stage 2 of sleep during a night’s sleep.

Stage 3: Non-REM sleep

During phases 3 and 4 of sleep, the deepest sleep occurs. Your eyes and muscles remain still, and your brain waves slow even further.

A good night’s sleep can do wonders for your health. Every time you rest, your body is recharging its batteries and mending damaged tissues and muscles. You need this phase in order to wake up the next day feeling awake and energized.

Stage 4: REM sleep

After you’ve fallen asleep, you’ll begin experiencing this stage about 90 minutes later. During REM sleep, your eyes move rapidly from side to side.

Your brain waves and eye movements increase during REM sleep. In addition, your heartbeat and breathing speed up.

REM sleep is frequently associated with dreaming. For learning and remembering purposes, this is a key time in the brain.

What Happens to Your Brain and Body During Sleep?

There are noticeable changes in almost every part of the body while sleeping. In order to go to sleep, the brain sends out a signal to the rest of the body that it is time to go to sleep.

Research shows that sleep strengthens the cardiovascular and immunological systems and helps regulate metabolism, although its molecular role is still not entirely understood. During sleep, the body undergoes significant transformations that can be observed.


During non-REM sleep, breathing slows down, and it reaches its lowest point during the third stage of deep sleep. During REM sleep, breathing might become more rapid and even erratic.

Heart Rate

Heart rate begins to slow in Stage 1 and slows to its slowest pace in Stage 3 just like breathing. When you’re deep in REM sleep, on the other hand, your heart rate is nearly as fast as it is when you’re up.

Muscle Tone

The body’s total energy expenditure decreases as muscles relax during non-REM sleep. Atonia, a muscle paralysis that occurs during the REM stage, is the most common symptom of REM sleep. As a result, the legs and limbs do not flail in response to dream content. During rapid eye movement sleep, the eyes dart back and forth under closed lids as the respiratory and ocular muscles remain active.

Brain Activity

Brain waves recorded while a person is sleeping reveal distinct patterns that correspond to various stages of sleep. Brain waves slow down significantly in the early stages of non-REM sleep; yet, there are frequent short bursts of brain activity in Stages 2 and 3.

During rapid eye movement (REM) sleep, brain waves change dramatically. REM sleep is associated with vivid dreams because of the increased brain activity that occurs during this period of sleep.

Non-REM sleep, even with diminished brain activity, is also believed to serve a role in facilitating healthy brain function while awake, even if REM sleep is required for critical cognitive capacities, including memory consolidation.


It is most common in REM sleep, but it can happen at any time of the night. Non-REM dreams, on the other hand, tend to be more imaginative, immersive, or odd, whereas REM dreams tend to be more fanciful, immersive, or bizarre.

Hormone Level

Many hormones are regulated by sleep and the body’s internal clock, or circadian rhythm, including:

  • Melatonin, a hormone that aids with sleep.
  • Growth hormone is a hormone that aids in the growth of bones, muscles, and a healthy metabolism.
  • Cortisol, a hormone produced in response to stress in the body.
  • Appetite-controlling hormones such as ghrelin and leptin

It’s possible that the quality of one’s sleep has an impact on one’s daytime hormone production, as hormone levels fluctuate throughout the various stages of sleep.

How much sleep do you need?

The amount of sleep you should get varies depending on your age. The CDC recommends the following lengths based on age, but this can vary from person to person.

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

What happens if you don’t get enough sleep?

Your body struggles to function effectively if you don’t get enough sleep. Chronic health problems affecting the heart, kidneys, blood, brain, and mental well-being have been related to sleep deprivation.

Adults and children alike are at greater risk of damage when they are sleep deprived. Car accidents can result from driver drowsiness, for example, which can lead to severe injuries or death.
What Happens During Sleep? - The Sleep Judge

Older folks who don’t get enough sleep have a higher chance of falling and breaking bones.

The following are possible effects of sleep deprivation:

  • The state of mind shifts.
  • anxiety.
  • sdepression.
  • lack of ability to remember.
  • a lack of concentration and focus.
  • sluggishness of movement
  • weariness.
  • a decreased resistance against disease.
  • An increase in body mass.
  • blood pressure is too high.
  • Diabetes mellitus is characterized by insulin resistance.
  • diabetes and heart disease are examples of long-term conditions.
  • higher mortality risk

What Happens if You Have Insomnia?

As a result, insomniacs are unable to sleep for as long as they would like, resulting in a lack of total sleep. Thus, people may not be able to get enough sleep at night, resulting in daytime fatigue and bad impacts on their mood and thinking, as well.

As a result of sleep deprivation, which frequently occurs with insomnia, sleep architecture can be disrupted. When people don’t get enough sleep, they are more likely to have a REM sleep rebound, which is when they spend an excessive amount of time in REM sleep. Too much brain activity can lead to irritability and exacerbate mental health problems like sadness and anxiety.

What Happens During Sleep if You Have a Sleep Disorder?

What happens when you sleep can be adversely affected by sleep disorders. Repetitive awakenings from restless leg syndrome or sleep apnea can disturb the regular sleep cycle, lowering the amount of restorative sleep. Circadian rhythm sleep-wake disorders can lead to sleep deprivation or aberrant sleep architecture.

What Happens When You Sleep Too Much?

Hypersomnia is a disorder in which one sleeps excessively. People with hypersomnia may find it difficult to stay awake during the day because of their severe daytime sleepiness. Hypersomnia has been linked to changes in sleep architecture, such as a decrease in deep sleep and an increase in non-rapid eye movement (NREM) sleep, which may impact total sleep quality.

Tips for Better Sleep

A better night’s sleep may be just a few productive sleep hygiene routines away:

  • It’s best if you can go to bed and wake up at the same time every day.
  • Establish a pre-sleep ritual that eases your mind and body into sleep.
  • If you can’t sleep, limit the amount of time you spend in bed.
  • The bedroom should be cold, dark, and quiet.
  • Stay away from heavy drinking, smoking, or exercising in the evening.
  • In the hours leading up to your night, refrain from using electronic devices with bright screens.

If you’re having trouble falling asleep, make an appointment with your doctor. Further lifestyle adjustments or a sleep study to discover a possible sleep issue may be recommended by them.

The bottom line

A good night’s sleep is essential to our physical and mental well-being. Rejuvenate your body and mind by allowing it to relax.

Sleep deprivation can cause memory and focus issues, a weakened immune system, and mood swings.

Adults typically require between seven and nine hours of sleep per night. Consult a physician or a sleep specialist if you’re having difficulty falling asleep or staying asleep at night. They are able to go to the root of the problem and help you sleep better.

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