What is sleep and why do we do it?
Sleep is a normal active state of all living creatures in which the mind and body are less responsive. It is believed that sleep is a restorative process.
We take sleep for granted, and most of us have probably never asked ourselves – what actually is sleep? The definition of ‘sleep’ is that it’s a naturally recurring state of mind that’s characterized by altered consciousness, the inhibition of almost all voluntary muscles, generally inhibited sensory activity, and a marked reduction in our interactions with our surroundings.
We distinguish sleep from wakefulness by our lack of ability to react to stimuli; however, sleep is more easily reversed than the states of being comatose or being in hibernation.
What is REM Sleep?
REM Sleep, or Rapid Eye Movement Sleep is just one of the five stages of sleep that people experience. REM is characterized by quick and random eye movements, which includes paralysis of the muscles during sleep. When we’re asleep, most animals’ systems move to an anabolic state in order to build up the immune, muscular, skeletal and nervous systems.
In non-human animals, sleep is observed in mammals, reptiles, birds, fish, amphibians, and in some form even in insects and nematodes.
Humans have an internal circadian (24-hour) biological clock which naturally promotes sleep at night, even without light fluctuations; whereas sleep is promoted during the day in nocturnal organisms, like rodents. But we do know that sleep patterns vary a lot among individual humans and among animals. Over the past 100 years, artificial light and industrialization have substantially changed human sleep habits, and today the diverse purposes and mechanisms of sleep are still the subject of ongoing research. It appears that sleep assists animals with improvements to both the body and the mind.
One well-known feature of sleep in humans is dreaming, and we’ve all experienced dreams. Whilst oftentimes difficult to describe, dreaming is an experience generally recounted in narrative form and which, while in progress, resembles waking life. However, later, it can usually be distinguished as fantasy.
There are many sleep disorders that humans suffer from; including dyssomnias such as Sleep Apnea, Hypersomnia and Insomnia; Bruxism; parasomnias such as REM Behavior Disorder and Sleepwalking, and circadian rhythm sleep disorders. Sleep disorders can lead to chronic sleep deprivation.
With both birds and mammals, sleep can be divided into two broad types: REM (rapid eye movement) sleep and NREM or non-REM (non-rapid eye movement) sleep. Each type of sleep can be associated with its own distinct set of neurological and physiological features. We know that REM sleep is associated with desynchronized and faster brain waves, dreaming, suspension of homeostasis, and loss of muscle tone. In fact, REM and non-REM sleep are so entirely different that physiologists have classified them as distinct behavioral states. The three major modes of consciousness, physiological regulation and neural activity are represented by REM, non-REM, and waking.
According to the proposed 1975-1977 Hobson and McCarley activation synthesis hypothesis, the alternation between non-REM and REM sleep can be defined by way of influential neurotransmitter systems that cycle reciprocally.
Why do we sleep?
Nobody knows why all creatures evolved the need to sleep. What we do know is that all creatures sleep – and that it is a basic biologic need just like breathing and eating. When we deprive ourselves of sleep, we have a rebound period in which we sleep more. This suggests that sleep is necessary for normal life. There are many studies that demonstrate that when subjects are deprived of sleep, that they do not function at their optimum.