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Theories of Sleep

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Theories of Sleep

Did you know that a person who lives to be approximately 70 years old would spend roughly 25 years of their life sleeping or attempting to sleep? Sleep is something that we all require. Our bodies control sleep in the same manner as eating, drinking, and breathing. This fact demonstrates that sleep and health are strongly connected.

  • What is sleep?
  • Why do we sleep?
  • What is the restorative theory of sleep?
  • What is the adaptive theory of sleep?
  • What is the brain plasticity theory of sleep?

Sleep Definition

Theories of Sleep woman sleeping StudySmarterWoman sleeping; the definition of sleep, pexels.com

Sleep is a state of unconsciousness brought on by our bodies. When this happens, the brain and body decrease responsiveness to external stimuli. During sleep, the noticeable changes in brain electrical activity are due to the brain's billions of nerve cells physically repairing themselves. The two forms of sleep are slow-wave sleep (SWS), also known as deep sleep, and rapid eye movement (REM), commonly known as dreaming sleep.

Stages of Sleep

The brain does not just shut down, but rather a series of finely coordinated actions put the brain to sleep in phases. We go through four stages of sleep: stages 1, 2, 3 (Non-REM), and REM (rapid eye movement) sleep. These phases develop continuously, from stage 1 to REM and then back to stage 1.

Non-REM

  1. Stage 1: Light sleep, slow eye movement, sudden muscle contractions, and easily awakened.

  2. Stage 2: Eye movement stops, your body gets ready to go into a deep sleep.

  3. Stage 3: No eye movement, deep sleep, waking up the individual is difficult. Sometimes bedwetting, nightmares, or sleepwalking occurs.

REM

  • Brain activity and eye movement increase.

  • Rise of heart rate and blood pressure.

  • Intense dreams.

  • It begins an hour and a half after you go to bed.

Benefits of Sleep

Getting adequate sleep provides several health benefits. The typical adult requires seven to nine hours of sleep, whereas a child's requirements vary depending on age and medical circumstances. While sleep quantity is vital, it is not the only factor in achieving a good night's sleep. Quality of sleep is just as necessary, if not more so. Below are some benefits you get from long-term quality sleep.

  • It helps to improve your immune system.

  • Your body releases good hormones for the heart and blood vessels.

  • Sleep helps regulate your metabolism to control blood sugar levels.

  • Sleep aids in relaxation and recovery from stress.

  • Aids in weight loss.

  • It helps to maintain physical balance.

  • Increase energy and alertness.

  • It improves your memory.

  • Aids in complex thinking like problem-solving, planning, and decision making.

  • Repairs damaged cells caused by stress, UV radiation, and other potentially dangerous substances.

Why Do We Sleep?

Scientists have looked at why we sleep from several viewpoints. For example, they've looked into what happens when people or some animals are sleep-deprived. They've also examined the sleep habits of different organisms in prior research to see if there are any comparisons to be made between species that could indicate something on the role of sleep.

There are numerous theories regarding several reasons why we sleep. However, no one specific theory will ever wholly explain these, but, taken together, they may reveal why humans sleep. The theory of sleep explanation can help us better understand the role of sleep in our lives. The four most common theories of sleep are adaptive theory, energy conservation theory, restoration theory, and brain plasticity theory.

Explanation of the Theories of Sleep

Let's explore the four most common theories a bit deeper.

Energy Conservation Theory

According to the energy conservation theory, sleep's main job is to minimize an individual's energy requirements and expenditure during certain times of the day or night, particularly when searching for food is inefficient.

In humans, energy metabolism slows down about ten percent during sleep, and it slows down considerably more in animals.

Body temperature and calorie needs decline during sleep compared to an awake state. Such research backs up the idea that one of sleep's key roles is to aid organisms in conserving their energy resources.

Theories of Sleep animal sleeping to conserve energy StudySmarterAnimal sleeping to conserve energy, pexels.com

The energy conservation theory is also reinforced by the fact that smaller species have faster metabolisms, which means they consume more energy and make their bodies heat, requiring them to sleep for more extended periods.

Still, cold-blooded creatures, such as snakes and fish, do not produce their body heat and have less evident and unambiguous sleep.

Restorative Theory

The restorative theory proposes that sleep promotes tissue repair and restoration. During wakefulness, many biological processes occur, and the body becomes depleted of its stores. The body tries to heal itself through muscle and tissue repair, protein synthesis, and hormone production necessary for growth, all of which occur largely during sleep. It's also worth noting that during non-REM sleep, bodily tissues mend and regenerate, whereas during REM sleep, brain tissue repairs.

Theories of Sleep woman waking up from a restorative sleep StudySmarterWoman waking up from a restorative sleep, pexels.com

In recent years, gathered human and animal investigations have supported these theories. The most remarkable is that animals without sleep for an extended time lose all immunological function and perish within weeks.

An excellent example of this theory would be the impact sleep has on sleepiness and alertness. Nerve cells create adenosine as a byproduct of their actions while we are awake. The accumulation of adenosine in the brain is regarded as one mechanism contributing to our feeling of exhaustion.

Caffeine intake, however, can block adenosine activities in the brain, keeping us attentive. Scientists believe that this accumulation of adenosine during waking hours promotes the urge to sleep, as adenosine builds up and remains high while we are awake. The body has an opportunity to eliminate adenosine from circulation while sleeping, which makes us feel more attentive when we wake up.

In light of this theory, a question arises if sleep causes healing and restoration while a person is asleep or if it just causes the body to rest. Some experts think that rest and the body processes during sleep are the true restorative components.

Chemical messengers such as growth hormones and testosterone are released during sleep, which causes some specialists to endorse the restorative view. In contrast, others view this as coincidental to sleep and not caused by it.

Adaptive Theory

The adaptive or evolutionary theory of sleep is one of the first theories that suggested sleep as an adaptive behavior to protect against natural hazards and predators. This behavior is thought to have evolved into what we currently call sleep due to natural selection.

Animals have sleeping patterns that adapt well to their environment. Cats, for example, may sleep 15 hours a day for long periods since they spend little time seeking food and have very few natural predators. However, foraging animals are more susceptible to predators and sleep between two to three hours in brief bursts.

Like hunger and thirst, sleep may reflect a basic physiological need that can only be met by sleeping and is critical to survival.

The adaptive theory of sleep psychology can partly explain why, for example, an animal would need to hide, especially at nighttime, when it is most vulnerable. The physiological requirement for sleep keeps the animal safe and assures that it will remain hidden away over time.

Brain Plasticity Theory of Sleep

Discoveries about sleep's link with changes in brain plasticity, which is the structure and organization of the brain, led to one of the most recent and intriguing theories as to why we sleep. Proponents of the brain plasticity theory of sleep emphasize that sleep improves our brain plasticity.

It seems that sleep can negatively or positively impact our cognitive function, for example, in the brain development of newborns and young children.

Infants sleep for roughly 13 to 14 hours each day, with around half spent in REM sleep when most dreams happen.

The quantity and quality of sleep have a major impact on learning and memory. Sleep appears to help learning and memory in two ways. First is, sleep deprivation affects focus and attention. Second, sleep helps memory consolidation, which is critical for successful learning.

Theories of Sleep - Key takeaways

  • The two forms of sleep are slow-wave sleep (SWS), also known as deep sleep, and rapid eye movement (REM), commonly known as dreaming sleep.
  • The adaptive theory of sleep is one of the first sleep theories that suggested sleep as an adaptive behavior to protect against natural hazards and predators.

  • Proponents of energy conservation theory believe that sleep's primary job is to minimize an individual's energy requirements and expenditure during certain times of the day or night, particularly when searching for food is inefficient.

  • In the restorative theory, it is stated that sleep promotes tissue repair and restoration.

  • Brain plasticity theory suggests an existing link between sleep and brain plasticity, wherein sleep enhances brain plasticity contributing to cognitive abilities and performance of tasks.

Frequently Asked Questions about Theories of Sleep

The theories of sleep are adaptive, energy conservation, restorative, and brain plasticity theory.

During sleep, the body tries to heal itself through muscle and tissue repair, protein synthesis, and hormone production necessary for growth.

The restorative theory proposes that sleep promotes tissue repair and restoration. The circadian theory of sleep refers to the body's job is to minimize an individual's energy requirements and expenditure during certain times of the day or night.

The restorative theory proposes that sleep promotes tissue repair and restoration. During wakefulness, many biological processes occur, and the body becomes depleted of its stores. 

Final Theories of Sleep Quiz

Question

Which of the following isn't a characteristic of REM sleep?

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Answer

The person is in a deep sleep.

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Question

Which shows an effect of long-term sleep deprivation?

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Answer

A person who lacks sleep is prone to falls and accidents.

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Question

All of the following are theories of sleep except:

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Answer

Capable Theory

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Question

Please choose the best answer. Evolutionary theory of sleep gives the idea that that sleep has evolved due to ________.


Show answer

Answer

Natural selection

Show question

Question

Which statement supports energy conservation theory?

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Answer

Body temperature and calorie needs decline during sleep compared to an awake state.

Show question

Question

In this theory, it is stated that sleep promotes body synthesis and repair.

Show answer

Answer

Restorative theory

Show question

Question

The ____________ is also reinforced by the fact that smaller species have faster metabolisms, which means they consume more energy and make their bodies heat, requiring them to sleep for more extended periods.

Show answer

Answer

Energy conservation theory

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Question

Please choose the best answer. Brain plasticity theory suggests that sleep improves the _______ and ________ of the brain.

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Answer

Structure and organization

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Question

An example of this theory is that infants sleep around 13-14 hours each day, with around half spent in REM sleep when most dreams happen.

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Answer

Brain plasticity theory

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Question

The evolutionary theory of sleep suggests sleep as ________ behavior to protect against natural hazards and predators.

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Answer

Adaptive

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Question

Non-REM sleep is characterized by the following except:

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Answer

It arrives an hour and a half after you go to bed.

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Question

Which statement is true about sleep?

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Answer

Not only quantity but also the quality of sleep have a major impact on learning and memory.

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Question

What is true about the theories of sleep?


  1. No one theory can explain why we sleep.

  2. Some of the theories have already been proven.

  3. These theories help us better understand the role of sleep.

  4. These theories don’t give a direct answer as to why we sleep.

Show answer

Answer

I, III and IV

Show question

Question

Energy metabolism is significantly reduced during sleep in _____ in humans and even more so in animals.

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Answer

10%

Show question

Question

All statements are true about sleep except:


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Answer

Sleep quantity is the only factor in achieving a good night's sleep.

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Question

Sleep is a state of unconsciousness during which the brain decrease responsiveness to ________ stimuli. 

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Answer

External

Show question

Question

True or False? Eye movement during sleep only occurs during REM. 

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Answer

False, eye movement occurs during stage 1 of non-REM but it is slow. 

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Question

During which stage of sleep is it difficult to be woken up?

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Answer

Stage 3

Show question

Question

At which point does REM sleep begin after you've gone to sleep?

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Answer

After 1.5 hrs

Show question

Question

True or False? The quality of sleep does not make a difference, only the quantity

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Answer

False. Quality of sleep matters just as much if not more. 

Show question

Question

Which of the following is not a benefit of long-term quality sleep?

Show answer

Answer

Weight gain

Show question

Question

True or False? Sleep can help repair damaged cells caused by UV radiation (i.e. too much sun). 

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Answer

True

Show question

Question

According to the adaptive theory of sleep, adaptive behaviors meant to protect us against natural hazards and predators have evolved into what we now call sleep due to ____________.

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Answer

natural selection

Show question

Question

In humans, energy metabolism slows down about _____ percent during sleep. 

Show answer

Answer

10

Show question

Question

According to the Energy Conservation Theory, why might smaller animals require more sleep?

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Answer

Their metabolism is faster so being awake consumes more energy and makes their bodies overheat. 

Show question

Question

What is adenosine?

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Answer

Adenosine is a chemical produced by nerve cells while we are awake. 

Show question

Question

How does adenosine affect our bodies?

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Answer

Contributes to our feeling of exhaustion

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Question

How does caffeine make us feel more awake?

Show answer

Answer

Caffeine blocks adenosine in the brain. 

Show question

Question

The Brain Plasticity Theory suggests that sleep can negatively or positively impact our __________ function.

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Answer

cognitive

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