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The Ins & Outs of Sleep:
Basic function:
Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles.[1] It is distinguished from wakefulness by a decreased ability to react to stimuli, and is more easily reversible than being in hibernation or a coma. Sleep is a heightened anabolic state, accentuating the growth and rejuvenation of the immune, nervous, skeletal and muscular systems. It is observed in mammals, birds, reptiles, amphibians and fish, and in some form also in insects and even simpler animals such as nematodes.
Physiology:
In mammals and birds, sleep is divided into two broad types: rapid eye movement (REM) and non-rapid eye movement (NREM or non-REM) sleep. Each type has a distinct set of associated physiological and neurological features. The American Academy of Sleep Medicine (AASM) further divides NREM into three stages: N1, N2, and N3, the last of which is also called delta sleep or slow-wave sleep.
Sleep proceeds in cycles of REM and NREM, usually four or five of them per night, the order normally being N1 → N2 → N3 → N2 → REM. There is a greater amount of deep sleep (stage N3) earlier in the night, while the proportion of REM sleep increases in the two cycles just before natural awakening.
Timing & the circadian clock:
Sleep timing is controlled by the circadian clock, sleep-wake homeostasis, and in humans, within certain bounds, willed behavior. The circadian clock—an inner timekeeping, temperature-fluctuating, enzyme-controlling device—works in tandem with adenosine, a neurotransmitter that inhibits many of the bodily processes associated with wakefulness. Adenosine is created over the course of the day; high levels of adenosine lead to sleepiness.[19] In diurnal animals, sleepiness occurs as the circadian element causes the release of the hormone melatonin and a gradual decrease in core body temperature. The timing is affected by one’s chronotype. It is the circadian rhythm that determines the ideal timing of a correctly structured and restorative sleep episode.[20]
Homeostatic sleep propensity (the need for sleep as a function of the amount of time elapsed since the last adequate sleep episode) must be balanced against the circadian element for satisfactory sleep.[21] Along with corresponding messages from the circadian clock, this tells the body it needs to sleep.[22] Sleep offset (awakening) is primarily determined by circadian rhythm. A person who regularly awakens at an early hour will generally not be able to sleep much later than his or her normal waking time, even if moderately sleep-deprived.
Amount of sleep:
The optimal amount of sleep is not a meaningful concept unless the timing of that sleep is seen in relation to an individual’s circadian rhythms. A person’s major sleep episode is relatively inefficient and inadequate when it occurs at the “wrong” time of day; one should be asleep at least six hours before the lowest body temperature.[25] The timing is correct when the following two circadian markers occur after the middle of the sleep episode and before awakening:[26] maximum concentration of the hormone melatonin, and minimum core body temperature.
Human sleep needs can vary by age and among individuals, and sleep is considered to be adequate when there is no daytime sleepiness or dysfunction.
Conflicting studies with regards to appropriate amount and time: many diseases are linked to sleep disfunction. Furthermore, sleep difficulties are closely associated with psychiatric disorders such as depression, alcoholism, and bipolar disorder.[35] Up to 90{43863adf827a03d4f1e5d69dc00969fa304fd977cb48f43b4a1f7a8f6cace59b} of adults with depression are found to have sleep difficulties. Dysregulation found on EEG includes disturbances in sleep continuity, decreased delta sleep and altered REM patterns with regard to latency, distribution across the night and density of eye movements.
Functions:
If sleep were not essential, one would expect to find:
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Animal species that do not sleep at all
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Animals that do not need recovery sleep after staying awake longer than usual
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Animals that suffer no serious consequences as a result of lack of sleep
Outside of a few basal animals that have no brain or a very simple one, no animals have been found to date that satisfy any of these criteria.
Wound healing has been shown to be affected by sleep. A study conducted by Gumustekin et al.[50] in 2004 shows sleep deprivation hindering the healing of burns on rats.
It has been shown that sleep deprivation affects the immune system. In a study by Zager et al. in 2007,[51] rats were deprived of sleep for 24 hours. When compared with a control group, the sleep-deprived rats’ blood tests indicated a 20{43863adf827a03d4f1e5d69dc00969fa304fd977cb48f43b4a1f7a8f6cace59b} decrease in white blood cell count, a significant change in the immune system. It is now possible to state that “sleep loss impairs immune function and immune challenge alters sleep,” and it has been suggested that mammalian species which invest in longer sleep times are investing in the immune system, as species with the longer sleep times have higher white blood cell counts.[52] Sleep has also been theorized to effectively combat the accumulation of free radicals in the brain, by increasing the efficiency of endogeneous antioxidant mechanisms.
There are multiple arguments supporting the restorative function of sleep. The metabolic phase during sleep is anabolic; anabolic hormones such as growth hormones (as mentioned above) are secreted preferentially during sleep. The duration of sleep among species is, broadly speaking, inversely related to animal size[citation needed] and directly related to basal metabolic rate. Rats, which have a high basal metabolic rate, sleep for up to 14 hours a day, whereas elephants and giraffes, which have lower BMRs, sleep only 3–4 hours per day.
Ontogenesis:
REM sleep appears to be important for development of the brain. REM sleep occupies the majority of time of sleep of infants, who spend most of their time sleeping. Among different species, the more immature the baby is born, the more time it spends in REM sleep. Proponents also suggest that REM-induced muscle inhibition in the presence of brain activation exists to allow for brain development by activating the synapses, yet without any motor consequences that may get the infant in trouble. Additionally, REM deprivation results in developmental abnormalities later in life.
Memory Processing:
Scientists have shown numerous ways in which sleep is related to memory. In a study conducted by Turner, Drummond, Salamat, and Brown (2007),[59] working memory was shown to be affected by sleep deprivation. Working memory is important because it keeps information active for further processing and supports higher-level cognitive functions such as decision making, reasoning, and episodic memory. The study allowed 18 women and 22 men to sleep only 26 minutes per night over a four-day period.
Dreaming:
Dreaming is the perceived experience of sensory images and sounds during sleep, in a sequence which the dreamer usually perceives more as an apparent participant than as an observer. Dreaming is stimulated by the pons and mostly occurs during the REM phase of sleep.
Insomnia is a general term describing difficulty falling asleep and staying asleep. Insomnia can have many different causes, including psychological stress, a poor sleep environment, an inconsistent sleep schedule, or excessive mental or physical stimulation in the hours before bedtime. Insomnia is often treated through behavioral changes like keeping a regular sleep schedule, avoiding stimulating or stressful activities before bedtime, and cutting down on stimulants such as caffeine. Patients are often counseled to improve their sleep environment by installing heavy drapes to shut out all sunlight, and keeping computers, televisions and work materials out of the sleeping area.
Yoga Nidra:
Yoga nidra or “yogi sleep” is a sleep-like state which yogis report to experience during their meditations. Yoga Nidra, lucid sleeping is among the deepest possible states of relaxation while still maintaining full consciousness. Lucid dreaming is the western term used to denote a practice similar to Yoga nidra. The distinguishing difference is the degree to which one remains cognizant of the actual physical environment as opposed to a dream environment. In lucid dreaming, we are only (or mainly) cognizant of the dream environment, and have little or no awareness of our actual environment.[1]
The practice of yoga relaxation[clarification needed] has been found to reduce tension and anxiety. The autonomic symptoms of high anxiety such as headache, giddiness, chest pain, palpitations, sweating, abdominal pain respond well. It has been used to help soldiers from war cope with posttraumatic stress disorder (PTSD).[2]
Yoga nidra refers to the conscious awareness of the deep sleep state, referred to as “prajna” in Mandukya Upanishad.[3]
Experimental evidence of the existence of a fourth state of unified, transcendental consciousness, which lies in the yoga nidra state at the transition between sensory and sleep consciousness, was first recorded at the Menninger Foundation in Kansas, USA in 1971.[6] Under the direction of Dr. Elmer Green, researchers used an electroencephalograph to record the brainwave activity of an Indian yogi, Swami Rama, while he progressively relaxed his entire physical, mental and emotional structure through the practice of yoga nidra.
What they recorded was a revelation to the scientific community. The swami demonstrated the capacity to enter the various states of consciousness at will, as evidenced by remarkable changes in the electrical activity of his brain. Upon relaxing himself in the laboratory, he first entered the yoga nidra state, producing 70{43863adf827a03d4f1e5d69dc00969fa304fd977cb48f43b4a1f7a8f6cace59b} alpha wave discharge for a predetermined 5 minute period, simply by imagining an empty blue sky with occasional drifting clouds.
Next, Swami Rama entered a state of dreaming sleep which was accompanied by slower theta waves for 75{43863adf827a03d4f1e5d69dc00969fa304fd977cb48f43b4a1f7a8f6cace59b} of the subsequent 5 minute test period. This state, which he later described as being ‘noisy and unpleasant’, was attained by ‘stilling the conscious mind and bringing forth the subconscious’. In this state he had the internal experience of desires, ambitions, memories and past images in archetypal form rising sequentially from the subconscious and unconscious with a rush, each archetype occupying his whole awareness.
Finally, the swami entered the state of (usually unconscious) deep sleep, as verified by the emergence of the characteristic pattern of slow rhythm delta waves. However, he remained perfectly aware throughout the entire experimental period. He later recalled the various events which had occurred in the laboratory during the experiment, including all the questions that one of the scientists had asked him during the period of deep delta wave sleep, while his body lay snoring quietly.
Such remarkable mastery over the fluctuating patterns of consciousness had not previously been demonstrated under strict laboratory conditions. The capacity to remain consciously aware while producing delta waves and experiencing deep sleep is one of the indications of the third state (prajna) out of the total of four states of consciousness described in the Mandukya Upanishad. This is the ultimate state of yoga nidra in which there are no dreams, but only the deep sleep state with retained consciousness/awareness. The result is a single, semi-enlightened state of consciousness and a perfectly integrated and relaxed personality.
Guna Cycle and appropriate living with ayurveda:
When to sleep and how it works:
6-10am kapha
10-2 amPitta
2-6 pm vata
6-10 pm Kapha
10-2 pm pitta
2-6am vatta
Just as the seasons have attributes of the doshas, so do the hours of the day. At sunrise, or about 6:00 A.M., the day’s cycle begins with Kapha. To take advantage of the Kapha cycle, it is best to awaken between 6:00 A.M. and 8:00 A.M. On awakening, you feel slow, relaxed, calm: all Kapha attributes. Kapha lasts until about 10:00 A.M. Even young children can reap the benefits of the Kapha hours by arising at sunrise.
From 10:00 A.M. to 2:00 P.M., it is Pitta time. You are at your most active and efficient during these hours. At noon, or lunchtime, your appetite is at its peak. Eat lunch between noon and 1:00 P.M. to use Pitta to your advantage. Lunch also should be your largest meal of the day. Parents should pack nutritious snacks and lunches for children that include the foods best for their particular mind/body type. This is the best time for children to take tests in school; and it is their most productive learning time.
From 2:00 P.M. to 6:00 P.M. is Vata time, when you are most alert and creative. A light dinner should be eaten before 6:00 P.M. if possible to take advantage of this energy.
The cycle repeats again in the evening hours. From 6:00 P.M. to 10:00 P.M. is Kapha time. Sunset brings the body rest and a slower pace. It is best to get to bed by 10:00 P.M. to take advantage of the natural Kapha rhythm of this time. For best digestion, eat dinner at least three hours before bedtime. Younger children who need more sleep should go to bed earlier so that they will still arise at sunrise.
Pitta time is 10:00 P.M. to 2:00 A.M., when Pitta keeps the body warm; the body also uses the Pitta heat to digest food and rebuild body tissues.
Vata time occurs again at 2:00 A.M. to 6:00 A.M. Vata creativity is expressed as active dreams. At this time, brain impulses are at their most active for the night.