Growth Hormone Release: Rem Vs. Nrem Sleep

Sleep is a complex process that plays a vital role in maintaining overall health and well-being. During sleep, our brain cycles through different stages, including non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. These stages have distinct characteristics and functions, contributing to various physiological processes. One important aspect of sleep is the release of growth hormones, which is influenced by the quality and depth of sleep. Upper airway obstruction (UAO), for instance, can disrupt normal growth hormone homeostasis, leading to growth retardation.

Growth hormone release is enhanced during slow-wave sleep

Sleep is a complex and mysterious body process, and researchers are still trying to understand how and why we sleep and what happens when we do.

During sleep, the body cycles through four stages, the first three of which are non-rapid eye movement (NREM) sleep, and the fourth is rapid eye movement (REM) sleep. Each stage has a unique function and role in maintaining the brain's overall cognitive performance.

NREM sleep is also known as quiet sleep, while REM sleep is also known as active sleep. During REM sleep, the eyes move rapidly in different directions, and brain activity is similar to when a person is awake. Dreams typically occur during REM sleep.

During NREM sleep, the brain is less active, and in the deeper stages, the breathing slows, and blood pressure drops. NREM sleep is divided into three stages:

NREM Stage 1

• A transition period between wakefulness and sleep.
• The brain slows down, along with heart rate, eye movements, and breathing.
• Muscles may twitch.
• This stage lasts for around 5 to 10 minutes.

NREM Stage 2

• A light sleep, where the person becomes less aware of their surroundings.
• The body temperature drops, eye movements stop, and breathing and heart rate become more regular.
• The brain produces bursts of rapid, rhythmic brain wave activity, known as sleep spindles, which are associated with memory consolidation.
• This stage lasts for about 20 minutes per cycle, and people spend about half of their total sleep time in this stage.

NREM Stage 3

• The deep sleep stage, where the person is harder to rouse, and if awakened, they would feel disoriented.
• Muscles are completely relaxed, blood pressure drops further, and breathing slows.
• The body starts its physical repairs during this stage, and getting enough of this deep sleep will leave a person feeling refreshed the next day.
• The brain consolidates declarative memories.
• This stage makes up about 25% of total sleep time in adults.

During the deep stages of NREM sleep, the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system. This is also when growth hormone release is enhanced.

Growth hormone (GH) secretion is associated with slow-wave sleep (SWS), which is also known as delta sleep. The release of GH is greatly enhanced during sleep, especially early in the night, and this is linked to the appearance of delta waves on electroencephalograms, characteristic of SWS. The release of GH is also associated with increased levels of growth hormone-releasing hormone (GHRH) in the hypothalamus.

Upper airway obstruction (UAO) can lead to abnormal GH homeostasis and growth retardation. Studies on rats have shown that UAO decreases GHRH levels, while treatment with ritanserin, a 5-HT2 receptor antagonist, can alleviate these effects by normalizing GHRH content, decreasing wake duration, and increasing the duration and depth of SWS.

In adults, the most significant pulse of GH secretion occurs shortly after the onset of sleep, during the first phase of SWS (stages III and IV). Approximately 70% of GH pulses during sleep coincide with SWS, and the amount of GH secreted during these pulses correlates with the amount of SWS.

Thus, growth hormone release is enhanced during slow-wave sleep, which is the deep sleep stage of NREM sleep.

Sleep-disordered breathing in children can cause growth retardation

Sleep-disordered breathing in children can have a significant impact on their health and development. One of the consequences of this condition is growth retardation, which occurs when there is a reduction in the release of the growth hormone (GH) during sleep. This reduction has been linked to an impairment in the GH-releasing hormone (GHRH) and its receptor (GHRHR).

Upper airway obstruction (UAO) is a common cause of sleep-disordered breathing in children, leading to abnormal GH homeostasis and growth retardation. Studies have shown that UAO decreases GHRH, GHRHR, and GH receptor levels, resulting in shorter sleep duration and slower growth.

The impact of sleep-disordered breathing on growth can be observed in children with enlarged tonsils and adenoids, a common physical cause of airway narrowing. Obstructive sleep apnea (OSA), where the airway is repeatedly blocked during sleep, affects approximately two to four percent of children. Enlarged tonsils and adenoids are often treated with surgical removal, which can improve sleep and behavior in the short and long term.

However, recent studies indicate that even mild sleep-disordered breathing or snoring may lead to growth retardation. This is because snoring can interrupt breathing, causing gasping and snorting noises that wake the child from sleep. As a result, the body's natural growth processes are disrupted, leading to slower growth and development.

In addition to growth retardation, sleep-disordered breathing in children can also cause irritability, daytime sleepiness, bedwetting, learning difficulties, cardiovascular issues, and obesity. Therefore, it is important for parents and healthcare providers to be vigilant in identifying and treating sleep-disordered breathing to ensure optimal health and development in children.

Sleepwalking occurs during NREM stage 3 sleep

Sleep is a complex and mysterious process that remains only partially understood by experts. During sleep, the body cycles through different stages, including REM (rapid-eye movement) sleep and non-REM (NREM) sleep. NREM sleep is further divided into three stages of increasing depth.

Sleepwalking, or somnambulism, is a sleep disorder that occurs during deep sleep, specifically during NREM stage 3 sleep. It involves walking or performing other complex behaviours while still mostly asleep. Sleepwalking episodes can range from brief periods of a few seconds to longer durations of up to 30 minutes or more. It is important to note that sleepwalking is distinct from simply walking during sleep, and can include a variety of actions such as sitting up in bed, preparing food, or even driving.

Sleepwalking is much more common in children than in adults, with an estimated prevalence of 5% in children and 1.5% in adults. It tends to have a genetic component, with a higher likelihood of occurrence if one or both parents have a history of sleepwalking. In addition, various factors such as sleep deprivation, certain medications, alcohol consumption, and stress can trigger sleepwalking episodes.

During NREM stage 3 sleep, the deepest stage of sleep, the brain produces slow and strong brain waves. This stage is crucial for the body's repair and recovery processes, as it provides an opportunity for the body to heal injuries and reinforce the immune system. Disruptions during this stage, such as sleepwalking, can impact the quality of sleep and contribute to feelings of fatigue or drowsiness during the day.

While sleepwalking itself is not typically dangerous, it can lead to injuries if the person trips or collides with objects. It is generally safe to gently guide a sleepwalker away from potential hazards and back to bed. However, it is important to be cautious as they may exhibit confused or aggressive behaviour upon awakening.

REM sleep is important for learning and memory

Sleep is essential for learning and memory. When we sleep, our brain cycles through different phases, including light sleep, deep sleep, and rapid eye movement (REM) sleep. The non-REM stages of sleep prime the brain for learning the next day, and a lack of sleep can reduce our ability to learn new things by up to 40%.

During sleep, our brain replenishes our ability to learn. Research has shown that a group of participants who napped between two rigorous learning sessions learned just as easily in the evening as they did at noon, whereas the group that didn't nap experienced a decrease in learning ability.

Sleep also improves our ability to recall information. Studies have found that sleep improves memory retention and recall by 20 to 40%. Stage 3 sleep, or deep non-REM sleep, is particularly important for memory retention and recall.

Additionally, sleep plays a crucial role in forming long-term memories. MRI scans suggest that the slow brain waves of stage 3 sleep act as a courier service, transferring memories from the hippocampus to more permanent storage sites in the brain.

Sleep also enhances our ability to solve problems creatively. Research has shown that participants who were woken up during REM sleep could solve 15 to 35% more complex puzzles than when they were woken up during non-REM sleep or during the day.

In conclusion, sleep is vital for learning and memory. It improves our ability to learn, recall information, form long-term memories, and solve problems creatively. Getting a good night's sleep before and after learning is essential for memory consolidation and cognitive performance.

Non-REM sleep is when the body repairs and regrows tissues

During non-REM sleep, the body's physical repairs take place. The body also builds bone and muscle, and strengthens the immune system. This is when the body slows down, and breathing and heart rate become more regular.

Non-REM sleep is divided into three stages. The first stage is a transition period between wakefulness and sleep, and it lasts for about five to ten minutes. The second stage is when the body temperature drops, and the person becomes less aware of their surroundings. The third stage is when the body enters its deepest sleep, and this is when the physical repairs and regrowth occur.

The amount of non-REM sleep a person gets decreases as they get older. Older people sleep more lightly and get less deep sleep. However, studies show that older people still need as much sleep as younger people.

Non-REM sleep is important for the body to repair and restore itself. It is during this time that the body slows down and focuses on healing and strengthening. Getting enough non-REM sleep is crucial for feeling refreshed and energised the next day.

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