Sleep is a very dynamic process regulated by various parts of the brain and the nervous system. Sleep promoting neurons in the brain become more active as we get ready to sleep. Neurotransmitters can “switch off” or dampen the activity of cells that signal arousal or relaxation.
GABA is associated with sleep, muscle relaxation and sedation. Norepinephrine and orexin (also called hypocretin) keep some parts of the brain active while we are awake. Other neurotransmitters that shape sleep and wakefulness include acetylcholine, histamine, adrenaline, cortisol, and serotonin. (Source: NIH – National Institute of Neurological Disorders and Stroke).
Sleep can be categorized by multiple cycles of rapid eye movement (REM) to non-rapid eye movement (NREM), where one cycle can last for approximately 90 minutes on average. The sleep cycle proceeds from REM to NREM in 4 stages (Note: Some others classify as 3 stages), namely, N1 to N4, in which the last stage refers to deep sleep. The autonomic nervous system regulates sleep; the intensity of sleep is induced by a progressive increase in parasympathetic activity and a corresponding decrease in sympathetic activity. Sleep disturbances and problems with the onset of sleep are clearly related to physical and mental status including tiredness, stress, anxiety, and excitement .
The hypothalamus, a peanut-sized structure deep inside the brain, contains groups of nerve cells that act as control centres affecting sleep and arousal. Within the hypothalamus is the suprachiasmatic nucleus (SCN) – clusters of thousands of cells that receive information about light exposure directly from the eyes and control our behavioral rhythm.
The pineal gland, located within the brain’s two hemispheres, receives signals from the SCN and increases production of the hormone melatonin, which helps us to sleep when darkness sets in. The peaks and valleys of melatonin over time are important for matching the body’s circadian rhythm to the external cycle of light and darkness.
It is generally perceived that one can enter into sleep easily and can experience good or deep sleep if one is in a relaxed state prior to going to bed. Second, sleep is affected by neurotransmitters, which have corresponding effects on suppressive or excitatory neurons in the brain. It is known that g-aminobutyric acidergic (GABAergic) neurons are inhibitory neurons and that glutamatergic neurons are excitatory neurons, which correspond with the promotion and inhibition of sleep, respectively. Antagonists of excitatory neurons are also substances known to promote sleep .
Alpha Brain Waves (low amplitude and slow regular frequency) are associated with a state of “wakeful relaxation.” That’s the state of mind you experience when meditating, being creative, or letting your mind wander in daydreaming. Alpha waves are also present during REM sleep.
Beta Brain Waves (lowest amplitude and faster irregular frequency) are associated with a state of “hyperarousal”. They dominate our normal waking state of consciousness when attention is directed towards cognitive tasks and the outside world. Beta is a ‘fast’ activity, present when we are alert, attentive, engaged in problem solving, judgment, decision making, or focused mental activity. The hyperarousal by Beta waves prevents deep sleep. Beta waves are lowest in a state of deep sleep and gradually increase before we wake up after REM sleep.
Theta Brain Waves (medium amplitude and low frequency) is associated with a state “transition to sleep”. Theta waves are present during REM sleep also. Theta brainwaves occur most often in sleep but are also dominant in deep meditation. In theta, our senses are withdrawn from the external world and focused on signals originating from deep within the subconscious mind.
Delta Brain Waves (high amplitude and low frequency) is associated with “deep sleep”. They are generated in deepest meditation and dreamless sleep. Neurons, which are not engaged in the processing of information, are firing all at the same time. Delta waves suspend external awareness and are the source of empathy. Healing and regeneration are stimulated in this state, and that is why deep restorative sleep is so essential to the healing process.
REM sleep has low amplitude and high frequency brain waves. It is also essential for good quality of sleep. Melatonin and L-Theanine are natural supplements known to improve the quality of sleep, without sedation.
Prolong Youth by leading an ‘enlightened and balanced life’
Ref 1: Rao T.P. et al, Journal of the American College of Nutrition, Vol. 34, No. 5, 436–447 (2015)
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