What happens during sleep?

The world of sleep is incredibly dynamic, even though it appears as a serene, restful state from the outside. Our brains orchestrate a fascinating symphony of activities during various sleep stages, each with its distinctive characteristics and benefits.

REM Sleep:


Rapid Eye Movement (REM) sleep, comprising 25% of our sleep cycle, is when the brain becomes highly active despite the body's immobility. This stage is where most dreaming occurs, often vivid and story-like, owing to increased brain activity. The eyes move rapidly in various directions, and the body experiences heightened physiological processes similar to wakefulness, including increased heart rate and irregular breathing.

REM sleep is crucial for cognitive functions, memory consolidation, and emotional regulation. The duration of REM cycles lengthens as the night progresses, with each subsequent REM stage becoming longer.

Understanding these sleep stages is fundamental as sleep isn't a monotonous journey but a dynamic process transitioning between light and deep phases. The distribution of time spent in each stage varies throughout the night, contributing to the overall quality of sleep.

Now, regarding snoring, it's indeed an important sign that often goes unnoticed as it occurs during sleep. Detecting whether one snores is crucial, as it could indicate potential sleep disturbances or sleep apnea, impacting overall health. Tools like sleep apps, recording devices, or consulting with a sleep specialist can aid in identifying and addressing snoring issues for better sleep quality and health outcomes. 

Non-REM Sleep Stages:


NREM sleep, constituting 75% of our total sleep, encompasses three distinct stages: 

Stage 1 (N1): This marks the onset of sleep, where brain activity slows down, and the individual transitions from wakefulness to sleep. It's a light sleep phase, where you can easily be roused. During this stage, muscle activity decreases, and people might experience hypnic jerks or sudden muscle contractions, sometimes accompanied by a sensation of falling. 

Stage 2 (N2): As sleep deepens, we enter N2, characterized by sleep spindles—short bursts of brain activity. Heart rate and breathing normalise, body temperature drops, and muscle tension relaxes further. This stage is pivotal in transitioning to deeper sleep. 

Stage 3 (N3): Formerly referred to as stages 3 and 4, this is the deepest sleep phase. Brain waves slow down significantly, and it's challenging to wake someone in this stage. It's during N3 that the body undergoes substantial restoration and healing. Sleepwalking, sleep talking, bedwetting (in children), and certain types of vivid dreams or nightmares often occur during this phase.

Now that we know what happens during sleep, it will be great to read more about "How to get good sleep at night?" and "Factors that affect sleep".


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Sleep Revitalizes your Mind, Body, & Heart

The body goes under many transformations, while it is in the state of rest during sleep. There are many essential functions that take place in the body such as tissue repair, memory and energy restoration, release of essential hormones, muscle relaxation, and others. While you are asleep, the brain releases indispensable hormones that promote tissue growth. This process helps your body rejuvenate from the daily hustle bustle. Moreover, tissue growth aids in the recovery from wounds or cuts. Sunita Kumar, Co-Director, Centre for Sleep Disorders, Loyola University Medical Centre, aptly remarks that during sleep the body produces more white blood cells, to fight countless bacteria and viruses1. The heart rate also registers a dip during sleep, which according to Ms. Kumar, strengthens the heart as it is at rest with lowered activity. Moreover, a good night’s sleep also reduces the chances of getting afflicted with heart diseases.

Good Sleep = Sharp Memory

Sleep is a time, when becomes sharp and strong. Sleep quantity and quality play a fundamental role in determining what one remembers and what one doesnt. Therefore, development of long-term memory (LTM) from short-term memory (STM) happens during sleep.  Scientific researches state that the brain follows a different mechanism for storing memories through the hippocampus and neo-cortex areas. Hippocampus helps you to remember your life experiences (childhood memories), while the neo-cortex is responsible for remembering the concepts you learn (name of a color). Communications and sync between the two, helps in learning new data and updating old ones.

Sleep Steers Hormonal Hunger

Sleep not only affects your energy levels and mental functions, but also regulates your body weight. Improper sleep is related to the increasing cases of obesity, worldwide2. Many hormones which regulate the feeling of hunger (ghrelin) and signal the feeling of being full (leptin), are all influenced by the quality of your sleep.  Leptin: This is also known as satiety hormone, which is produced by the fat cells of the body. It prevents overeating by sending signals to the brain that the body does not require more food, as there is enough to fuel the body.  Ghrelin: This hunger hormone is produced in the gastrointestinal tract, which signifies the body that there is need for food. This hormone rises in the body, when you feel hungry and decreases when you have consumed some food.  Studies show that people who have disrupted patterns of sleep - have larger appetite, because of higher ghrelin secretion and lowered secretion of leptin. This imbalance in the secretion of these hormones is a result of improper sleep patterns3.