In this post, we looked at the concept of sleep, stages of sleep, benefits and importance of sleep, causes of lack of sleep and its effects.
What is Sleep?
Sleep is a state of reduced mental and physical activity in which consciousness is altered and sensory activity is inhibited to a certain extent.
INTRODUCTION
The most pronounced physiological changes in sleep occur in the brain. The brain uses significantly less energy during sleep than it does when awake, especially during non-REM sleep. In areas with reduced activity, the brain restores its supply of adenosine triphosphate (ATP), the molecule used for short-term storage and transport of energy. In quiet waking, the brain is responsible for 20% of the body’s energy use, thus this reduction has a noticeable effect on overall energy consumption. Sleep increases the sensory threshold.
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In other words, sleeping persons perceive fewer stimuli, but can generally still respond to loud noises and other salient sensory events. During slow-wave sleep, humans secrete bursts of growth hormone. All sleep, even during the day, is associated with the secretion of prolactin. Humans may suffer from various sleep disorders, including dyssomnias such as insomnia, hypersomnia, narcolepsy, and sleep apnea; parasomnias such as sleepwalking and rapid eye movement sleep behavior disorder; bruxism; and circadian rhythm sleep disorders.
The use of artificial light has substantially altered humanity’s sleep patterns. Common sources of artificial light include outdoor lighting and the screens of electronic devices such as smartphones and televisions, which emit large amounts of blue light, a form of light typically associated with daytime. This disrupts the release of the hormone melatonin needed to regulate the sleep-cycle.
The Concept of Sleep
Sleep is a state of reduced mental and physical activity, in which consciousness is altered, and sensory activity is inhibited to a certain extent. During sleep, there is a decrease in muscle activity, and interactions with the surrounding environment are significantly reduced. While sleep is different from wakefulness in terms of the ability to react to stimuli, it still involves active brain pat During sleep, your body is working to support healthy brain function and maintain your physical health. In children and teens, sleep also helps support growth and development. Getting inadequate sleep over time can raise your risk for chronic (long-term) health problems. terns, making it more reactive than a coma or disorders of consciousness.
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Stages Of Sleep
Each night you take a rollercoaster ride through the different phases of sleep. Though you’re unaware of what goes on while you’re snoozing, your brain and body are in an active state. Each stage of sleep plays a different role in how you feel the next day. The following are stage of sleep which helps your brain, restores your body, and shows if you’re striking a good balance between the stages each night. Sleep occurs in five stages: wake, N1, N2, N3, and REM. Stages N1 to N3 are considered non-rapid eye movement (NREM) sleep, with each stage a progressively deeper sleep. Approximately 75% of sleep is spent in the NREM stages, with the majority spent in the N2 stage. A typical night’s sleep consists of 4 to 5 sleep cycles, with the progression of sleep stages in the following order: N1, N2, N3, N2, REM. A complete sleep cycle takes roughly 90 to 110 minutes. The first REM period is short, and, as the night progresses, longer periods of REM and decreased time in deep sleep (NREM) occur.
Wake/Alert: EEG recording: beta waves – highest frequency, lowest amplitude (alpha waves are seen during quiet/relaxed wakefulness) The first stage is the wake stage or stage W, which further depends on whether the eyes are open or closed. During eye-open wakefulness, beta waves predominate. As individuals become drowsy and close their eyes, alpha waves become the predominant pattern.
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N1 (Stage 1) – Light Sleep (5%): EEG recording: theta waves – low voltage. This is the lightest stage of sleep and begins when more than 50% of the alpha waves are replaced with low-amplitude mixed-frequency (LAMF) activity. Muscle tone is present in the skeletal muscle, and breathing tends to occur at a regular rate. This stage lasts around 1 to 5 minutes, consisting of 5% of total sleep time.
N2 (Stage 2) – Deeper Sleep (45%): EEG recording: sleep spindles and K complexes
This stage represents deeper sleep as your heart rate and body temperate drop. It is characterized by the presence of sleep spindles, K-complexes, or both. Sleep spindles are brief, powerful bursts of neuronal firing in the superior temporal gyri, anterior cingulate, insular cortices, and thalamus, inducing calcium influx into cortical pyramidal cells. This mechanism is believed to be integral to synaptic plasticity. Numerous studies suggest that sleep spindles play an important role in memory consolidation, specifically procedural and declarative memory. K-complexes are long delta waves that last for approximately one second and are known to be the longest and most distinct of all brain waves. K-complexes have been shown to function in maintaining sleep and memory consolidation. Stage 2 sleep lasts around 25 minutes in the first cycle and lengthens with each successive cycle, eventually consisting of about 45% of total sleep. This stage of sleep is when bruxism (teeth grinding) occurs.
N3 (Stage 3) – Deepest Non-REM Sleep (25%): EEG recording: delta waves – lowest frequency, highest amplitude. N3 is also known as slow-wave sleep (SWS). This is considered the deepest stage of sleep and is characterized by signals with much lower frequencies and higher amplitudes, known as delta waves. This stage is the most difficult to awaken from, and, for some people, even loud noises (> 100 decibels) will not awaken them. As people age, they tend to spend less time in this slow, delta wave sleep and more time in stage N2 sleep. Although this stage has the greatest arousal threshold, if someone is awoken during this stage, they will have a transient phase of mental fogginess, known as sleep inertia. Cognitive testing shows that individuals awakened during this stage tend to have moderately impaired mental performance for 30 minutes to an hour. This is the stage when the body repairs and regrows tissues, builds bone and muscle and strengthens the immune system. This is also the stage when sleepwalking, night terrors, and bedwetting occurs.
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REM (25%): EEG recording: beta waves – similar to brain waves during wakefulness. REM is associated with dreaming and is not considered a restful sleep stage. While the EEG is similar to an awake individual, the skeletal muscles are atonic and without movement, except for the eyes and diaphragmatic breathing muscles, which remain active. However, the breathing rate becomes more erratic and irregular. This stage usually starts 90 minutes after you fall asleep, with each of your REM cycles getting longer throughout the night. The first period typically lasts 10 minutes, with the final one lasting up to an hour. REM is when dreaming, nightmares, and penile/clitoral tumescence occur.
Important characteristics of REM:
- Associated with dreaming and irregular muscle movements as well as rapid movements of the eyes
- A person is more difficult to arouse by sensory stimuli than during SWS
- People tend to awaken spontaneously in the morning during an episode of REM sleep
- Loss of motor tone, increased brain O2 use, increased and variable pulse and blood pressure
- Increased levels of ACh
- The brain is highly active throughout REM sleep, increasing brain metabolism by up to 20%.
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Health benefits of sleep
Getting enough sleep has many benefits. It can help you:
- Get sick less often
- Stay at a healthy weight
- Lower your risk for serious health problems, like diabetes and heart disease
- Reduce stress and improve your mood
- Think more clearly and do better in school and at work
- Get along better with people
- Make good decisions and avoid injuries — for example, drowsy drivers cause thousands of car accidents every year
Importance Of Sleep
Sleep plays a vital role in good health and well-being throughout your life. The way you feel while you are awake depends in part on what happens while you are sleeping. During sleep, your body is working to support healthy brain function and maintain your physical health. In children and teens, sleep also helps support growth and development. Getting inadequate sleep over time can raise your risk for chronic (long-term) health problems. It can also affect how well you think, react, work, learn, and get along with others. Learn how sleep affects your heart and circulatory system, metabolism, respiratory system, and immune system and how much sleep is enough.
Causes Of Lack of Sleep and Its Effects
Common causes of lack of sleep are chronic insomnia. Insomnia is difficulty getting to sleep or staying asleep for long enough to feel refreshed the next morning. which include: Stress, Concerns about work, school, health, finances or family can keep your mind active at night, making it difficult to sleep. Stressful life events or trauma — such as the death or illness of a loved one, divorce, or a job loss — also may lead to insomnia.
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If you have insomnia, you may:
- find it difficult to fall asleep
- lie awake for long periods at night
- wake up several times during the night
- wake up early in the morning and not be able to get back to sleep
- not feel refreshed when you get up
- find it hard to nap during the day, despite feeling tired
- feel tired and irritable during the day and have difficulty concentrating
Occasional episodes of insomnia may come and go without causing any serious problems, but for some people it can last for months or even years at a time. Persistent insomnia can have a significant impact on your quality of life. It can limit what you’re able to do during the day, affect your mood, and lead to relationship problems with friends, family and colleagues.
Effects of lack of sleep
If we don’t get the recommended 8 hours of sleep each night, we do know that the impact on our health can be devastating. Let’s take a deeper look at the top 10 effects of long-term sleep deprivation. An ongoing lack of sleep has been closely associated with hypertension, heart attacks and strokes, obesity, diabetes, depression and anxiety, decreased brain function, memory loss, weakened immune system, lower fertility rates and psychiatric disorders.