An Overview of Sleep

 Introduction

Sleep is a complex neurological process that determines the healthy physiological as well as healthy biochemical and healthy mental stability of a person. For proper growth and development and for proper secretion of growth hormone, proper sleep is utmost necessary in babies. “The scientist around the world has estimated that for proper development of a baby, 16 – 20 hours of sleep is necessary”1. Medical field has now given utmost importance in sleep studies because due to improper sleep “many diseases like hypertension, coronary diseases, stroke, psychological impairment, diabetes and many metabolic diseases are growing rapidly in day to day life”2.

            Social activity of the person are changing in relative manner leading to de-arrangement of sleep pattern and also changing the circadian pattern of sleep. The medical practitioners are getting lots of sleep disorder patients having a history of work pressure, stress, anxiety, monetary problems, de-arranged home environment, poor health issues, having long standing diseases and many other social impacts leading to sleepless night.

            “Ayurveda has given special emphasis to sleep (Nidra) and has regarded sleep as one of the pillars for the maintenance of good health and a stable mind. Happiness, stability, virility, knowledge, nourishment and life can be achieved only after getting proper sleep. Improper sleep will lead to sorrow, instability emaciation, weakness and death”3.

Definition of Sleep:- 

1. "The periodic state of mind of many living things with the absence of wakefulness and loss of consciousness and is accompanied by typical body posture with muscle relaxed and also there is change is brain activity and physiological function"4. .

2. “Sleep is defined as unconsciousness from which the person can be aroused by sensory or other stimuli. It is distinguished from coma from which the person cannot be aroused”5.

Non Rapid Eye Movement Sleep

A synchronized EEG pattern is associated with N.R.E.M sleep and sleep spindles and K complexes and high voltage slow wave activity that are collected from the entire cortical surface show delta frequency between 0.5 Hz and 4.0 Hz. N.R.E.M is divided into stage 2,3 and 4. in stage 2, sleep spindles and K complexes are less than 20% of S.W.A in the recordings and corresponds light sleep with a low threshold to awakening. stage 3-4 with S.W.A recording of at-least 20 % corresponds to deep sleep.

    The whole brain participates in the physiology of non-REM sleep. Scientifically it has been seen that peripheral and spinal impulses can modify the activity of the brain by increasing EEG synchronization and producing Short Wave Activity. These features occur after the coetaneous nerve stimulation, visual, diffuse or permanent illumination of retina or origination of afferent volleys in the vagus nerve. Ascending synchronization is also seen generated in the spinal cord after suppression of the trigeminal afferents, after lesion or blockage of the spinal cord producing decrease of Short wave activity in the EEG. Active and resting periods are still seen in organized manner when separation of the medulla and caudal pons from the brain stem structures are done and these features are absent in lesions in the medullary and midpontine. Sleep spindles and delta SWA cannot be observed in decerebrate animals in which the brain stem has been released from prosencephalic influences, even though these preparations show the behavioral and bioelectric REM sleep signs. Isolation of the forebrain transacted at the intercollicular level of cats diminishes the brain stem influence but still generates the bioelectric activity giving the pattern of NREM sleep. Several clinical, lesions and stimulating experiments have made it possible to describe NREM synchronic hypnogenicity that includes pre-optic, forebrain and anterior hypothalamic regions. Higher density activity during NREM sleep is seen in neurons generating from the ventral lateral pre-optic area and median pre-optic nucleus. Clinical studies in the thalamus demonstrate that ascertain electrophysiological manifestation that characterize NREM sleep  pattern6. Studies on thalamocortical and corticothalamic cellular bases demonstrates that combination of the intrinsic electrophysiological properties of the thalamic and cortical neurons is responsible for the generation of sleep spindles and delta SWA oscillation in the EEG during NREM sleep.

Source:- 

1. Adams and Victor's Principles of Neurology, Tenth Edition, Allan H. Ropper, Martin A. Samuels, Joshua P. Klein.

2. Adams and Victor's Principles of Neurology, Tenth Edition, Allan H. Ropper, Martin A. Samuels, Joshua P. Klein.

3. Significance of Sleep: Ayurvedic Perspective , Prajapati Seema, Paliwal M, https://www.ijhsr.org/IJHSR_Vol.9_Issue.1_Jan2019/36.pdf.

4. (https://www.merriam-webster.com/dictionary/sleep).

5. Guyton and Hall Textbook of Medical Physiology, Hall E Joshua.

6. Functional Anatomy of non-REM sleep, Isabel de Andres, Miguel garzon , https://www.researchgate.net/publication/51824007_Functional_anatomy_of_non-REM_sleep

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