Rem, Nrem, And Half-Conscious Sleep: What's The Deal?

Sleep is a state of reduced consciousness and responsiveness to the environment, with decreased voluntary muscle activation and inhibited sensory modalities. It is a restorative process that is essential for the body and brain to function properly.

During sleep, the body cycles between two main types of sleep: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep is further divided into four stages, each with unique characteristics and brain activity patterns. It is characterised by slow, low-frequency brain waves, and the absence of rapid eye movement and muscle paralysis. During the deepest stage of NREM sleep, the body repairs tissues, builds bone and muscle, and strengthens the immune system.

On the other hand, REM sleep is marked by increased brain activity, similar to the level of activity when awake. The eyes move rapidly, and the body is temporarily paralysed, preventing people from acting out their dreams. REM sleep stimulates areas of the brain involved in learning and memory and is important for processing emotions and emotional memories.

Throughout the night, the body typically cycles through these two types of sleep, spending about 75-80% of total sleep time in NREM sleep and the remaining 20-25% in REM sleep.

REM sleep is when the brain is active and dreams occur

Sleep is a complex and mysterious process, and while asleep, the human body cycles between being awake and asleep. There are two main types of sleep: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep is further divided into four stages, with the cycle starting with NREM sleep and ending with a shorter period of REM sleep.

REM sleep is characterised by relaxed muscles, quick eye movement, irregular breathing, elevated heart rate, and increased brain activity. The brain activity during REM sleep is similar to the brain activity when one is awake. Dreams typically occur during REM sleep, and they tend to be more vivid than dreams during non-REM sleep. The first cycle of REM sleep occurs about 60 to 90 minutes after falling asleep, and it usually lasts about 10 minutes. With each new cycle, the duration of REM sleep increases, with the final one lasting up to an hour.

REM sleep plays a crucial role in several functions, including dreaming, memory, emotional processing, and brain development. During this stage, the brain repairs itself, processes emotional experiences, and transfers short-term memories into long-term memories. Additionally, REM sleep stimulates the areas of the brain that aid in learning and memory.

The amount of REM sleep needed varies with age. Newborn babies spend up to eight hours in REM sleep daily, while adults only require an average of two hours of REM sleep each night. Overall, REM sleep is essential for the proper functioning of the human body and mind.

NREM sleep is when the brain is less active and the body repairs itself

NREM sleep is divided into four stages, each with unique characteristics, including variations in brain wave patterns, eye movements, and muscle tone. The first stage of NREM sleep is the transition between being awake and falling asleep. This stage usually lasts a few minutes and it is easy to wake someone up during this stage. The second stage is light sleep, during which heart rate and breathing slow down, and body temperature drops. This stage can last between 10 and 25 minutes. The third and fourth stages are deep sleep. During these stages, it is harder to wake someone up, and they would feel disoriented if they were woken up. In adults, the third and fourth stages make up about 25% of total sleep time.

During NREM sleep, the body repairs and regenerates itself. This is when the body takes advantage of being in a very deep sleep stage to repair injuries and reinforce the immune system. The brain is also active during NREM sleep, with bursts of brain activity that are thought to be the brain organizing and storing memories.

NREM sleep is important for physical repair and recovery. Being less active during sleep makes it easier for the body to heal injuries and repair any issues that occurred while awake. This is also why being sick makes people feel more tired and in need of more rest. NREM sleep is also important for brain maintenance, with the brain using this time to reorganize and catalog information and memories.

The cycle of NREM and REM sleep repeats throughout the night, with people typically cycling through four or five times. The first stage of sleep is always NREM sleep, followed by a shorter period of REM sleep, and then the cycle starts over again.

Sleep cycles and stages were discovered using electroencephalographic (EEG) recordings

The sleep cycles and stages were discovered using electroencephalographic (EEG) recordings. Electroencephalography (EEG) is a non-invasive and painless method of measuring brain activity through the scalp. It detects the general activity of the cortex by measuring small (~10 uV) fluctuations in voltage.

EEG readings depict differences in both amplitude and frequency over time. An increase in amplitude on an EEG indicates a higher degree of synchronous activity of cortical neurons, whereas the frequency of an EEG indicates how often neural synchrony occurs.

The first overnight sleep recordings were performed by Loomis and colleagues, and several groups improvised this and gave rise to the beginnings of sleep staging. However, it was only 17 years later that Aserinsky recognised rapid eye movement (REM) sleep, which led to the birth of modern methods of sleep staging.

In 1968, a committee of experts chaired by Rechtschaffen and Kales established the rules for the scoring of sleep in normal human adults. From this coding, five sleep stages were identified: one REM stage and four non-REM (NREM) sleep stages. Each stage consists of a number of physiological variables, which tend to occur in concert.

Using EEG, scientists discovered three distinct NREM phases based on neuron activity patterns: NREM1, NREM2, and NREM3 sleep.

Currently, readings collected via EEG are considered to be the gold standard for measuring the stages of sleep.

Sleepwalking typically occurs during NREM stage 3 sleep

Sleepwalking, or somnambulism, typically occurs during the third stage of non-rapid eye movement (NREM) sleep. This stage is also known as slow-wave sleep or deep sleep, and is characterised by low-frequency, high-amplitude delta waves. During this stage, an individual's heart rate and respiration slow dramatically, and it becomes more difficult to wake them up.

Sleepwalking is considered a parasomnia, which is a type of sleep disorder involving disruptive motor activity during sleep. While sleepwalking is most commonly associated with NREM Stage 3 sleep, it can occur at any time during sleep in some individuals with the disorder.

NREM sleep is the first phase of sleep, consisting of three stages, followed by a shorter period of REM sleep. During NREM sleep, the brain is not as active as it is during REM sleep, and in the deeper stages of NREM sleep, the body's breathing slows and blood pressure drops.

NREM Stage 3 is the deep sleep stage, and it is harder to rouse someone during this stage. If awakened, the person would feel disoriented for a few minutes. In adults, NREM Stage 3 sleep makes up about 25% of total sleep time. During this stage, the body repairs and regenerates tissues, builds bone and muscle, and strengthens the immune system.

During NREM Stage 3 sleep, the muscles are completely relaxed, and the body's blood pressure and breathing slow down. This is the stage when the body starts its physical repairs, and getting enough of this type of sleep will make one feel refreshed the next day. The brain also consolidates declarative memories, such as general knowledge, facts, and personal experiences.

While NREM sleep is associated with physical repairs and the strengthening of the immune system, REM sleep is important for learning and memory. During REM sleep, the brain is active, and dreams typically occur. REM sleep stimulates areas of the brain that help with learning and memory, and the brain also repairs itself and processes emotional experiences during this stage.

Sleep is important for memory consolidation

There are two types of sleep: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep is divided into stages 1, 2, 3, and 4, representing a continuum of relative depth. Each has unique characteristics including variations in brain wave patterns, eye movements, and muscle tone. Circadian rhythms, the daily rhythms in physiology and behavior, regulate the sleep-wake cycle.

Sleep has been proposed as serving an energy-saving function, the restoration of energy resources and the repairing of cell tissue, thermoregulation, metabolic regulation, and adaptive immune functions. However, these functions could be likewise achieved in a state of quiet wakefulness and would not explain the loss of consciousness and responsiveness to external threats during sleep. These prominent features of sleep strongly speak for the notion that sleep is mainly "for the brain".

During REM sleep, your eyes move rapidly and your brain is active. Your brain activity is similar to its activity when you’re awake. Dreams typically happen during REM sleep. During non-REM sleep, your brain is not as active. In the deeper stages of non-REM sleep, your breathing slows down, and your blood pressure drops.

The brain seems to produce the templates for proteins according to a kind of internal clock, but these templates aren’t translated into actual proteins without sleep. This seems to further link the need for sleep with healthy synaptic function and protein production.

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