What happens during sleep?

While asleep, a person might seem at rest and peace. However, a lot happens at the subconscious level, in the mind. Your body might be inactive while you sleep, but your brain is still functioning, and at times at a rapid pace. The different stages of sleep can be categorized in 4 stages, and divided into NREM and REM sleep.

There are some specific functions and body changes associated with every stage of sleep, which contribute to multiple benefits of sleep. Let us talk about each stage of sleep in detail, to provide you with a clear conception.

Non-REM Sleep Stage

As we start to fall asleep, we enter the Non-Rem or NREM or Non-Rapid Eye Movement stage of sleep. This is further divided into three stages. According to National Sleep Foundation, NREM comprises 75% of the total sleep.

Stage 1- The first stage of sleep is termed as N1. In this stage, sleep is lightest, and you can be easily awakened. You drift in and out of sleep in this stage, and people often experience muscle contraction, followed by a sensation of falling. Muscle activity and brain waves start to slow down in this stage.

Stage 2- Also called N2, this stage marks the onset of sleep. The heart rate and breathing are normal in this stage, and you slowly become completely unaware of your surroundings. This is the stage where sleep spindles occur. The temperature of the body falls, and thereafter, muscles are relaxed.

Stage 3- The N3 stage defines what was formerly known as stage 3 and 4. This is the stage where sleep is deepest The body becomes still, and the temperature falls even lower, with a drop in the heart rate. As this is the deepest stage of sleep, it is quite difficult to be awakened from this stage. It is why people often feel disoriented and dizzy after waking up in the middle of this stage. This stage marks healing and functions like sleepwalking, sleep talking, bedwetting (in children), or nightmares. Several nervous system changes, and learnings are also related to N3.

REM Sleep

According to the National Sleep Foundation, REM or Rapid Eye Movement forms 25% of the total sleep. Dreams mostly occur in this stage, along with ‘lucid’ dreaming - as the brain is pretty active. During REM sleep, the eyes move quickly in different directions.

The body and brain are also energized during REM sleep. Initially, REM occurs and reoccurs every 90 minutes after falling asleep, and this duration gets longer as the total sleep time increases. Daytime performance of people is also hugely dependent on REM sleep.

These sleep stages are a lot more than a pattern, in which sleep proceeds through the entire sleep time. Each stage has a role to play as you move from a state of light sleep to deep sleep. Moreover, the amount of time one spends in each stage keeps changing. A complete sleep is a work of all the stages, distributed through one’s course of sleep.

As mentioned earlier, snoring is one of the prime indicators of bad sleep at night, and can have negative implications on your health, if ignored. It is one indicator that might not be easily detected as it occurs during sleep. Therefore, you must find ways to detect whether you snore, or not.

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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.

Now that we have talked about why sleep is essential, in the next section - we will be discussing in detail some of the significant parameters, that define good or bad sleep.