Sleep is a physiological process the body undergoes daily, during which certain functions, such as perception and sensation, slow down to replenish the energy lost throughout daily activities. In this article, we will explore the two stages of sleep, their durations, and the key functions the body performs during sleep—scientifically and in detail. Stay with us until the end.
What Are the Stages of Sleep?
Sleep consists of two primary stages that the body cycles through sequentially:
Stage 1 sleep: Non-Rapid Eye Movement (NREM) Sleep
Non REM sleep stage is the first main stage of natural sleep, consisting of three sub-stages. Each sub-stage lasts approximately 7–40 minutes, with the entire NREM phase spanning about one to two hours:
Stage 1 (N1)
This is the transition phase into sleep, occurring as some body and brain functions begin to slow down gradually. It lasts for about (7 minutes). During this stage, the body does not fully relax, making it easy to wake up due to any disturbance. In the absence of interruptions, the body transitions smoothly into the next stage of sleep.
Stage 2 (N2)
This stage lasts (10–25 minutes), during which muscles relax, body temperature decreases, breathing and heart rates slow down, and eye movements cease. Although these functions significantly reduce, minimal activity remains, making the body more resistant to external disturbances or stimuli that could cause awakening.
Stage 3 (N3)
Known as deep sleep, this stage involves even greater muscle relaxation and further reduction in bodily functions. It becomes difficult to wake a person in this phase. During this stage, the body undergoes recovery, growth, cellular regeneration, and immune cell renewal. This phase typically lasts )20–40 minutes).
Stage 2 sleep: Rapid Eye Movement (REM) Sleep
During REM sleep, all voluntary muscles are temporarily paralyzed except for involuntary muscles like those of the digestive system, respiratory system, heart, and eyelids. Despite closed eyes, rapid eye movements occur, giving this stage its name.
The brain is most active during this stage, and dreams are most vivid. The body typically enters REM sleep after at least (90 minutes) of sleep. If you sleep longer through the night, the REM phase tends to extend.
What Happens to the Body During Sleep?
Smooth transitions between sleep stages contribute to internal balance and energy restoration. The following changes occur in the body during sleep:
- The parasympathetic nervous system, which regulates organ and bodily functions, relaxes.
- Blood pressure slightly decreases.
- Breathing and heart rates slow below normal levels.
- Body temperature drops by one degree, from 37°C to 36°C.
- The brain processes the day’s events, discarding trivial ones and storing significant ones as memories.
- Key neurotransmitters like serotonin, dopamine, and norepinephrine are regulated, stabilizing their levels, which helps reduce stress, alleviate anxiety, and improve mood throughout the next day.
- Skin cells renew, becoming more vibrant, hydrated, and elastic.
- The body releases immune compounds called cytokines, which circulate to combat pathogens, inflammation, infections, or cancerous cells. This explains the increased urge to sleep when sick.
In Summary
Normal Sleep stages helps rejuvenate your energy and strength to start fresh every morning. To ensure restful and comfortable sleep, choose the most peaceful times at home, avoid sources of disturbance, refrain from consuming caffeinated beverages in the evening, and minimize anxiety, stress, and overthinking. Additionally, invest in appropriate orthopedic pillows and mattresses. All these factors contribute to a more seamless and restful sleep cycle, enabling you to wake up feeling energized.
