A mystery called 'Sleep' ( 'துயில்' எனும் புதிர் )

rajamohansub
Mar 29, 2023
5 min read

From the dawn of the universe, most of the insects, animals and humans sleep for a certain period of time during the daytime and/or in the night ( diurnal or nocturnal) and awake always perplexed and intrigued, knowing little or nothing about the time passed in sleeping. Even after many years of continued research on brain activity and physiological patterns of sleeping, scientists as well as normal humans still have only a vague notion of what sleep is.

In simple terms, sleep is a period of rest during which the sleeping person loses awareness of their surroundings temporarily. It is a biological function for recovery, energy conservation and survival, but how the recovery takes place is still a mystery. It is important for learning, memory, emotional regulation, neural development , cardiovascular and metabolic functions. It is a well known fact that a good quality sleep is critical for good health and overall quality of life. https://doi.org/10.1164/rccm.201504-0767ST. ( The importance of healthy sleep - American Thoracic society)

'Melatonin' is the hormone which induces sleep in a human being is secreted by the pineal gland located within the brain's two hemispheres, on receipt of the signal from the master clock of the body (Suprachiasmatic nucleus (SCN) located on the anterior region of the hypothalamus). The master clock coordinates and controls all the biological clocks in the body including of the circadian rhythm which is a biological rhythm based on the day - night cycle.

Circadian Rhythm and the mechanism of sleep:

Circadian rhythm is the physical, mental and behavioral changes that follow a 24 hour cycle and it is a biological rhythm and what most people are concerned with, is the diurnal sleep - wake cycle. Biological clocks built in the human body (in each tissues and organs) are natural timing devices which are regulating the cycle of circadian rhythm.

The master clock (SCN) is very sensitive to light, and it receives electrical signals from the retina of the eyes through the optic nerves which influences the signals sent by the master clock to pineal gland to have sleep-wake cycle. During the day the light exposure causes the master clock to send signal to be alert and as the night falls, it initiates the production of melatonin and transmitting signals to help us to sleep during the night.

In 2017, three US researches Jeffrey C Hall ( University of Maine), Michael Rosbash ( Brandeis university) and Michael W. Young (Rockefeller university) were awarded Nobel prize for the circadian rhythms research.

https://nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx

If you think that your sleeping process takes place at a stretch in one go, you may have to reconsider your thinking. As per the latest knowledge about sleep, a typical night's sleep consists of 4 to 5 cycles ( each cycle of 90-110 minutes duration) and each sleep cycle occurs in stages:

N1 stage - Light sleep ( 5%)

N2 Stage - Deep sleep ( 45%)

N3 Stage - Deepest sleep (25%)

These three stages are considered as Non Rapid Eye Movement (NREM) sleep

Rapid Eye Movement (REM) Stage - 25%, associated with dreaming and not considered as a restful sleep stage.

An illustration of stages of sleep:

https://www.ncbi.nlm.nih.gov/books/NBK526132/#:~:text=Sleep%20occurs%20in%20five%20stages,N2%2C%20N3%2C%20and%20REM. - Mechanism of sleep , sleep stages

https://www.youtube.com/watch?v=lgZbH0S-76I ( ஐந்து நிலை தூக்கம் - இறை அன்பு, முதன்மை செயலாளர், தமிழ் நாடு அரசு )

https://youtu.be/A198Tdrknsc - Resetting the circadian rhythm

How much sleep one needs :

As per Centers for Disease control and Prevention's (CDC) recommendation, depending on the various stages of a person, different sleep hours are required.

It may be noted that for elderly persons , the recommended sleep hours are 7-9 hours.

Compared to humans, many animals sleep more, with brown bat leading the pack with almost 20 hours of sleep per day.

Fun facts about sleep:

Humans spend about one third of their life in sleeping, yet they remember little or none of it.
Many animals sleep by standing
Cattles can sleep by standing, but they dream only while lying down
Some dogs when dream, awake suddenly, whine and run very fast
Insects and spiders have daily periods of reduced activity but not sleep
Migratory birds and aquatic animals like whales and dolphins exhibit Uni- hemispheric sleep, where, only half of their brain sleep at a time.

Sleep disorders:

Sleep related difficulties may affect everyone in one time or another. Some of the major sleep disorders and a brief description of them is as below:

Insomnia : Most common sleep disorder - inability to initiate or maintain sleep - waking up too early in the morning . Possible reasons: Stress, Irregular bed time, blue light, depression,
Circadian sleep disorder : Non synchronization of one's sleep-wake cycle against the desired sleep - wake cycle. Possible reasons: Jet lag, shift work .
Sleep apnea : make periodic gasping or snorting noises by which the sleep would be interrupted. Experience excessive daytime sleepiness.
Narcolepsy : Excessive daytime sleepiness including irresistible sleepiness with sudden muscle weakness
Sleep walking (Somnambulism) : Getting up and walking around while in a state of sleep - occurs early in the night - mostly with children - disoriented or confused for a short time. Possible reasons: sleep deprivation, stress, sleep schedule disruptions.

Sleeping tips for elders:

As we age, we may experience changes in our sleeping patterns, such as becoming sleepy earlier, waking up earlier, or experiencing fragmented sleep. As the age increases, body produces less growth hormones and thus the production of melatonin is reduced and elders experience more fragmented sleep ( not deep sleep) and wake up often during the night .

Below are the suggested tips by Harvard Medical School for better night's sleep:

Exercise: Brisk walking keeps us up less often at night by boosting the effect of sleep hormone, melatonin. Timing of exercise shall not be too close to bed time
Make the sleeping place comfortable: Ideally a quiet, dark and cool environment with out any distraction like television
Adopt a sleep ritual: Going to bed at the same time daily help signal the body and mind that it is the bed time. Taking bath and calming music to unwind before bed.
Eat but not too much : Avoid eating a big meal within two or three hours of bed time. Eat moderately not to have a grumbling stomach or an overly full belly.
Avoid alcohol and caffeine: Chocolate, coffee and alcohol are stimulants which disrupts sleep during night. Also stay away from anything acidic , such as citrus fruits and juices
De-stress : do not take day time worries to bed. Stress is a stimulus and it activates 'fight or flight hormone', adrenaline that works against sleep. Try deep breathing exercises, inhale slowly and deeply and then exhale
Get checked : If you experience an urge to move your legs ( restless leg syndrome, may be due to low levels of iron in brain), snoring with breathing pauses ( obstructive sleep apnea) and a burning pain in the stomach, chest or throat ( Gastroesophageal reflux disease (GRD)) and keeping you awake at night then consult a doctor.
Minimize daytime naps

https://www.health.harvard.edu/newsletter_article/8-secrets-to-a-good-nights-sleep.

Sleep and interrogation:

Historically, sleep deprivation has been used in law enforcement, military organizations as a tool to compel disclosure and/confessions. Sleep deprivation, along with waterboarding and confinement, are the 'enhanced interrogation techniques' used by various interrogation agencies including CIA . But psychology professionals and Human & Civil Rights activists doubt the efficacy of this interrogation method and want this method should be totally discontinued and stooped forthwith.

https://www.policechiefmagazine.org/interview-considerations-sleep-deprivation/

Sleep and dreams

Dreaming is still a mystery of human cognition, although it has been studied experimentally for more than a century. Dreaming was first investigated on an experimental level in the 19th century and Mary Whiton Calkins (1893) , an American psychologist, published the first statistical results about dreaming.