What Is the Function of Sleep?

What Is the Function Of Sleep?

Sleep is necessary for optimal health. In truth, we need sleep to exist, just as we need to consume food and water. So it’s no surprise that we spend around one-third of our lives sleeping.

What Is the Function of Sleep?

Sleep is necessary for optimal health. In truth, we need sleep to exist, just as we need to consume food and water. So it’s no surprise that we spend around one-third of our lives sleeping.

  • Many biological activities occur during sleep, including the brain’s storage of new knowledge and eliminating harmful waste.
  • Nerve cells connect and rearrange, promoting normal brain function.
  • The body heals cells, regenerates energy, and secretes hormones and proteins.

These functions are essential to our general wellness. Our bodies cannot operate properly without them.

Let’s look more closely at why we sleep and what happens if we don’t get enough.

There is still a lot we don’t know about the function of sleep. However, it is commonly understood that there is more than one reason why humans need to sleep. It is most likely required for a variety of biological reasons.

Scientists have discovered that sleep benefits the body in many ways. The most prevalent hypotheses and causes are discussed further down.

Source - Casper

Cellular Regeneration

Another view, known as the restorative hypothesis, contends that the body needs sleep to repair itself.

Sleep, according to the theory, permits cells to heal and renew. This is supported by a number of critical processes that occur during sleep, including:

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

Conserving Energy

We need sleep to save energy, according to the energy conservation theory. Sleeping helps us to minimise our calorie needs by operating at a reduced metabolic rate for a portion of the day.

This theory is supported by the fact that our metabolic rate decreases during sleep. According to research, 8 hours of sleep for humans may result in a daily energy savings of 35% compared to total wakefulness.

According to the energy conservation hypothesis of sleep, the primary goal of sleep is to lower a person’s energy intake during periods of the day and night when getting food is inconvenient and inefficient.

Brain Function

According to the brain plasticity concept, sleep is necessary for brain function. It enables your neurons, or nerve cells, to restructure.

Your brain’s glymphatic (waste clearance) system clears waste from the central nervous system when you sleep. It cleans your brain of hazardous byproducts that accumulate during the day. This enables your brain to function properly when you wake up.

According to research, sleep improves memory function by turning short-term memories into long-term memories and by deleting, or forgetting, unnecessary information that would otherwise overload the nervous system.

Many elements of brain function are influenced by sleep, including:

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

Emotional Wellbeing

Similarly, sleep is essential for emotional well-being. During sleep, brain activity rises in parts of the brain that control emotion, promoting optimal brain function and emotional stability.

Sleep increases activity in the following areas of the brain:

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

The amygdala is one example of how sleep may help regulate mood. The fear response is controlled by this area of the brain, which is situated in the temporal lobe. It is what guides your response when confronted with perceived danger, such as a stressful event.

When you get adequate sleep, your amygdala is able to react in a more adaptive manner. However, when you are sleep deprived, your amygdala is more inclined to overreact.

According to research, sleep and mental health are inextricably linked. Sleep disruptions, on the one hand, may contribute to the beginning and development of mental health difficulties, but mental health concerns can also contribute to sleep disturbances.

Sufficient Insulin Function

Insulin is a hormone that aids in the utilisation of glucose, or sugar, by your cells for energy. Insulin resistance, on the other hand, occurs when your cells do not react effectively to insulin. This may result in excessive blood glucose levels and, in the long run, type 2 diabetes.

Sleep may help to prevent insulin resistance. It keeps your cells healthy, allowing them to quickly absorb glucose.

The brain also utilises less glucose when sleeping, which aids the body in regulating overall blood glucose levels.


Sleep is crucial in maintaining a good immune system. Sleep deprivation has been shown in studies to suppress the immune response and allow the body to be more vulnerable to infections.

While you sleep, your body produces cytokines, which are proteins that help your body fight infection and inflammation. It also generates antibodies and immunological cells. These chemicals work together to keep the body healthy by eliminating unwanted microorganisms.

That’s why, whether you’re unwell or anxious, you need to get enough rest. During these periods, the body requires an increase in immune cells and proteins.

Heart Health

While the underlying reasons are uncertain, experts believe that sleep promotes heart health. This is due to the relationship between heart disease and lack of sleep.

According to the Centers for Disease Control and Prevention (CDC), an average adult needs 7 hours of sleep every night. Getting less than that on a daily basis can lead to a variety of health issues, many of which are detrimental to your heart’s health.  

Sleep deprivation is linked to a number of risk factors for heart disease, including:

  • high blood pressure
  • increased sympathetic nervous system activity
  • increased inflammation
  • elevated cortisol levels
  • weight gain
  • insulin resistance

What Occurs When You’re Sleeping?

Your body goes through four different stages of sleep. This cycle repeats many times during the night for variable amounts of time ranging from 70 to 120 minutes each. During a 7- to 9-hour sleep period, the stages usually repeat four to five times.

The pattern consists of two primary sleep phases: non-rapid eye movement (non-REM) sleep and rapid eye movement (REM) sleep. Three stages of non-REM sleep and one stage of REM sleep are included in the four stages of sleep.

Non-REM sleep, as the names imply, is defined by the lack of eye movements, while REM sleep, when dreaming occurs, is characterised by rapid eye movements.

The four stages of sleep are as follows.

Stage 1: Non-REM sleep

When you initially fall asleep, you are at Stage 1. Your brain waves, heart rate, and eye movements all calm down when your body enters light slumber.

This stage lasts around 7 minutes.

Stage 2: Non-REM sleep

This stage consists of light sleep before deeper sleep.

Your body temperature drops, your eye movements stop, and your heart rate and muscles relax. Your brain waves momentarily surge and then gradually calm down.

You spend the majority of your sleep time in stage 2 throughout the night.

Stage 3: Non-REM sleep

Deep sleep starts in stages 3 and 4. Your muscles and eyes do not move, and your brain waves slow even further.

Deep sleep is rejuvenating. Your body refuels its energy reserves and restores cells, tissues, and muscles. This phase is required if you want to feel alert and refreshed the following day.

Stage 4: REM sleep

This phase begins around 90 minutes after you fall asleep. REM sleep causes your eyes to move fast from side to side.

REM sleep leads to an increase in brain waves and eye movements. Your heart rate and breathing both increase.

Dreaming is common during REM sleep. This period is particularly crucial for learning and memory since your brain processes information.

How much sleep do you need?

The quantity of sleep you should get varies on your age. It differs from person to person, however, the CDC recommends the following time frames depending on age:

  • 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

Side Effects Of Sleep Deprivation

Your body has a difficult time functioning properly if you don’t get enough sleep. Sleep deprivation has been related to chronic health issues, including the heart, kidneys, blood, brain, and mental health.

Sleep deprivation is also linked to an increased risk of injury in adults and children. Drowsiness among drivers, for example, may lead to major automobile accidents and even fatalities.

Poor sleep is linked to an increased risk of falls and broken bones in the elderly.

Sleep deprivation may have the following consequences:

  • mood changes
  • anxiety
  • depression
  • poor memory
  • poor focus and concentration
  • poor motor function
  • fatigue
  • weakened immune system
  • weight gain
  • high blood pressure
  • insulin resistance
  • chronic diseases, like diabetes and heart disease
  • increased risk of early death

The Bottom Line

Sleep is essential for our health and well-being. It allows your body and mind to heal, rejuvenate, and re-energise.

You may encounter adverse effects such as impaired memory and attention, reduced immunity, and mood changes if you do not get enough sleep.

The average adult needs 7 to 9 hours of sleep every night. Talk to your doctor or a sleep expert if you’re experiencing difficulties sleeping. They may help you identify the underlying problem and enhance the quality of your sleep.



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