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
Woman 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
Stage 1: Light sleep, slow eye movement, sudden muscle contractions, and easily awakened.
Stage 2: Eye movement stops, and your body gets ready to go into a deep sleep.
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 in heart rate and blood pressure.
Intense dreams.
It begins an hour and a half after you go to bed.
What are the Theories of Sleep?
Theories have been put forward to explain why sleep is essential for survival. Some theories include inactivity, energy conservation, restoration, and brain plasticity theories.
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.
Animal 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.
Woman 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.
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