Lately, I was reading about sleep, so I thought why not to Post something about it as well. So, here I’m with another doctoricious post!
About sleep, Allah subhanahu wa ta’ala mentioned in the Holy Quran that “Among His signs is sleep” (30:23) and “and made your sleep for rest” (78:9).
Essentially, sleep is important to the body functioning, promoting bodily rest and rejuvenation in the neurons and other cells that are replaced or repaired during times of sleep. Sleep has also been proposed to conserve energy, detoxify the brain, control thermoregulation within the brain, and consolidate the memory.
While sleeping, a person goes through stages of two types of sleep that alternate with each other. They are called
(1) slow-wave sleep, in which the brain waves are strong and of low frequency, and
(2) rapid eye movement sleep (REM sleep), in which the eyes undergo rapid movements despite the fact that the person is still asleep.
Most part of the sleep is of slow-wave variety; which is deep, restful sleep and is experienced by a person during the first hour of sleep REM sleep, on the other hand, occurs in episodes that occupy about 25% of the sleep time in young adults; each episode normally recurs about every 90 minutes. This type of sleep is not so restful, and it is usually associated with vivid dreaming.
Further divided into four stages.
Stage one: Light Sleep
During the first stage of sleep, we’re half awake and half asleep. Our muscle activity slows down and slight twitching may occur. This is a period of light sleep, meaning we can be awakened easily at this stage.
Stage two: True Sleep
Within ten minutes of light sleep, we enter stage two, which lasts around 20 minutes. The breathing pattern and heart rate start to slow down. This period accounts for the largest part of human sleep.
Stages three and four: Deep Sleep
During stage three, the brain begins to produce delta waves, a type of wave that is large (high amplitude) and slow (low frequency). Breathing and heart rate are at their lowest levels.
Stage four is characterised by rhythmic breathing and limited muscle activity.
Bouts of REM sleep lasting 5 to 30 minutes usually appear on the average every 90 minutes. When the person is extremely sleepy, each bout of REM sleep is short and may even be absent. Conversely, as the person becomes more rested through the night, the durations of the REM bouts increase.
Although we are not conscious, the brain is very active – often more so than when we are awake. This is the period when most dreams occur. Our eyes dart around (hence the name), our breathing rate and blood pressure rise. However, our bodies are effectively paralysed, said to be nature’s way of preventing us from acting out our dreams.
After REM sleep, the whole cycle begins again.
- Inactive theory: suggest that inactivity at night is protective to harm to the animals from the predators, also called adaptive/evolutionay theory
- Energy Conservative theory: suggests that the primary function of sleep is to reduce an individual’s energy demand and expenditure during part of the day or night, especially at times when it is least efficient to search for food.
- Restorative theory: suggests that sleep in some way serves to “restore” what is lost in the body while we are awake. Sleep provides an opportunity for the body to repair and rejuvenate itself.
- Brain plasticity theory: suggests that sleep is correlated to changes in the structure and organization of the brain – phenomenon known as plasticity.
- Consolidation of memory: episodic memory is converted into long term memory.
- Previously, its thought that sleep is a time when your body and brain shut down for rest and relaxation but we know that in REM sleep brain is highly active, secretion of some hormones and memory is also consolidated, besides, brain is the regulatory organ which is never completely shut down!
- Also its thought that Nap is a waste of time but researches reveals they can be restorative and help counter some of the impaired performances during the day.