Sleep is a naturally recurring state of rest in which your body and mind undergo various physiological changes. It is essential for overall health and well-being, as it allows your body to recover, repair, and rejuvenate. Sleep is divided into different stages that cycle throughout the night in a pattern known as the sleep cycle.

The two main categories of sleep are Rapid Eye Movement (REM) sleep and Non-Rapid Eye Movement (NREM) sleep. Each of these categories consists of distinct stages with specific characteristics:

Stage N1 (NREM-1): This is the transitional stage between wakefulness and sleep. It's a light sleep stage during which muscle activity decreases, and the body may experience sudden muscle contractions known as hypnic jerks. Eye movement is slow, and brain waves become irregular.

Stage N2 (NREM-2): This is a deeper sleep stage characterized by a decrease in heart rate and body temperature. Brain waves become slower and punctuated by sleep spindles (short bursts of rapid brain activity) and K-complexes (sharp waveforms). Most of our total sleep time is spent in this stage.

Stage N3 (NREM-3): Also known as slow-wave sleep (SWS) or deep sleep, this stage is characterized by slow, synchronized brain waves called delta waves. It's the deepest and most restorative sleep stage, essential for physical recovery, immune function, and memory consolidation. Growth hormone release often occurs during this stage.

Rapid Eye Movement(REM) sleep is characterized by rapid eye movements, increased brain activity, and vivid dreaming. It is the stage where most dreaming occurs. REM sleep is important for cognitive processes, emotional regulation, and memory consolidation.

During the sleep cycle, which typically lasts around 90 to 110 minutes, you progress through various stages of NREM and REM sleep. A typical sleep cycle might consist of stages N1, N2, N3, N2, and then REM sleep. As the night progresses, the proportion of REM sleep increases while the amount of deep N3 sleep decreases.

A complete sleep cycle involves transitioning through all these stages multiple times throughout the night. The order and duration of these stages can vary from person to person and change with age. Quality sleep with balanced time spent in each stage is crucial for overall health, cognitive function, emotional well-being, and physical recovery.