question: Why do you get tired after sleeping for a long period of time?
comment: After a certain point, you have to expend energy to keep sleeping. It's the exact definition of "more trouble than it's worth."
passages: Sleep is known to be cumulative. This means that the fatigue and sleep one lost as a result, for example, staying awake all night, would be carried over to the following day. Not getting enough sleep a couple days cumulatively builds up a deficiency and that's when all the symptoms of sleep deprivation come in. When one is well rested and healthy, the body naturally spends not as much time in the REM stage of sleep. The more time one's body spends in REM sleep, causes one to be exhausted, less time in that stage will promote more energy when awakened.
   BULLET::::- : A pulsus paradoxus is an exaggerated decrease in systolic blood pressure during inspiration. It can indicate certain medical conditions in which there is reduced cardiac output, such as cardiac tamponade or constrictive pericarditis. Also known as the Pulse Paradox.
  
  BULLET::::- : The "second wind" is a sudden period of increased wakefulness in individuals deprived of sleep that tends to coincide with the individual's circadian rhythm. Although the individual is more wakeful and aware of their surroundings, they are continuing to accrue sleep debt and thus, are actually exacerbating their sleep deprivation.
  
  Section::::Chemistry.
   Because disrupted sleep is a significant contributor to fatigue, a diagnostic evaluation considers the quality of sleep, the emotional state of the person, sleep pattern, and stress level. The amount of sleep, the hours that are set aside for sleep, and the number of times that a person awakens during the night are important. A sleep study may be ordered to rule out a sleep disorder.
  
  Depression and other psychological conditions can produce fatigue, so people who report fatigue are routinely screened for these conditions, along with drug abuse, poor diet, and lack of physical exercise, which paradoxically increases fatigue.
   An even lighter type of sleep has been seen in rats that have been kept awake for long periods of time. In a process known as local sleep, specific localized brain regions went into periods of short (~80 ms) but frequent (~40/min) NREM-like states. Despite the on and off periods where neurons shut off, the rats appeared to be awake, although they performed poorly at tests.
  
  Section::::Physiological effects.:Other effects.:Weight gain.
   BULLET::::- "Sleep deprivation and cumulative fatigue effects" describe how individuals who fail to have an adequate period of sleep (7–8 hours in 24 hours) or who have been awake longer than the conventional 16–17 hours will suffer sleep deprivation. A sleep deficit accumulates with successive sleep-deprived days, and additional fatigue may be caused by breaking daily sleep into two shorter periods in place of a single unbroken period of sleep. A sleep deficit is not instantly reduced by one night's sleep; it may take two or three conventional sleep cycles for an individual to return to unimpaired performance.
   Fatigue is generally considered a more long-term condition than sleepiness (somnolence). Although sleepiness can be a symptom of medical issues, it usually results from lack of restful sleep, or a lack of stimulation. Chronic fatigue, on the other hand, is a symptom of a greater medical problem in most cases. It manifests in mental or physical weariness and inability to complete tasks at normal performance. Both are often used interchangeably and even categorized under the description of 'being tired.' Fatigue is often described as an uncomfortable tiredness, whereas sleepiness is comfortable and inviting.
  
  Section::::Diagnosis.:Measurement.
   Sleepiness can be dangerous when performing tasks that require constant concentration, such as driving a vehicle. When a person is sufficiently fatigued, microsleeps may be experienced. In individuals deprived of sleep, somnolence may spontaneously dissipate for short periods of time; this phenomenon is the second wind, and results from the normal cycling of the circadian rhythm interfering with the processes the body carries out to prepare itself to rest.
  
  The word "somnolence" is derived from the Latin "somnus" meaning "sleep".
  
  Section::::Causes.
  
  Section::::Causes.:Circadian rhythm disorders.
   BULLET::::- Adenosine levels in the brain progressively increase with sleep deprivation, and return to normal during sleep. Upon awakening with sleep deprivation, high amounts of adenosine will be bound to receptors in the brain, neural activity slows down, and a feeling of tiredness will result
   Finally, on the opposite end of the spectrum, other patients may report feeling that they have slept much longer than is observed. It has been proposed that this experience be subclassified under sleep state misperception as "positive sleep state misperception", "reverse sleep state misperception", and "negative sleep state misperception".
  
  Section::::Symptoms and diagnosis.:Diagnostic criteria.
   The International Civil Aviation Organization (ICAO) that codifies standards and regulations for international air-navigation defines fatigue as: "A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical activity) that can impair a crew member's alertness and ability to safely operate an aircraft or perform safety related duties." 
   One neurochemical indicator of sleep debt is adenosine, a neurotransmitter that inhibits many of the bodily processes associated with wakefulness. Adenosine levels increase in the cortex and basal forebrain during prolonged wakefulness, and decrease during the sleep-recovery period, potentially acting as a homeostatic regulator of sleep. Coffee and caffeine temporarily block the effect of adenosine, prolong sleep latency, and reduce total sleep time and quality.
  
  Section::::Timing.:Social timing.
   Starting with the old adage "Once there was a little girl..." you come across a little girl and her parents, all wearing crowns. The little girl is wide awake claiming she is not tired. Her parents take this almost as a regular occurrence and require that she at least put on her pajamas, wash her face, brush her teeth. The little girl keeps repeating that she is not tired but climbs into bed and under the sheets since that is where she is the most comfortable. She then proceeds to ask her parents if everything thing goes to sleep. The parents then proceed to go through a list of animals and their habits of sleeping. They discuss the family dog, the cat, bats, snails, bears, and whales. The little girl proclaims that she knows an animal that sleeps a lot. We then finally come across the tiger in the jungle, where the little girl tells her parents that he sleeps to stay strong. The parents agree that sleep is good to stay strong then say goodnight even though the little girl claims she is still not sleepy. Her parents know what will happen and agree that she can stay awake all night long. After the long discussion, the little girl goes through all the processes that the animals go through and ends up fast asleep.
   During a night's sleep, a small amount of time is usually spent in a waking state. As measured by electroencephalography, young females are awake for 0–1% of the larger sleeping period; young males are awake for 0–2%. In adults, wakefulness increases, especially in later cycles. One study found 3% awake time in the first ninety-minute sleep cycle, 8% in the second, 10% in the third, 12% in the fourth, and 13–14% in the fifth. Most of this awake time occurred shortly after REM sleep.
   Sleep deprivation and cumulative fatigue effects describe how individuals who fail to have an adequate period of sleep (7–8 hours in 24 hours) or who have been awake longer than the conventional 16–17 hours will suffer sleep deprivation. A sleep deficit accumulates with successive sleep-deprived days, and additional fatigue may be caused by breaking daily sleep into two shorter periods in place of a single unbroken period of sleep. A sleep deficit is not instantly reduced by one night's sleep; it may take two or three conventional sleep cycles for an individual to return to unimpaired performance.
   Section::::Effect of Oversleeping.
  
  There have been many connections made between oversleeping and certain disorders. Many of these have been made without any identifiable reason for correlation, and are mainly observational. WebMD reports that sleep apnea may cause oversleeping because of disruptions in the normal sleep cycle, that individuals who sleep more may be more prone to headaches because of neurotransmitters imbalances, back pain can increase with oversleeping because a certain level of physical activity is not being maintained, and that oversleeping may be correlated with depression and higher death rates.
   Sleepiness can also be a response to infection. Such somnolence is one of several sickness behaviors or reactions to infection that some theorize evolved to promote recovery by conserving energy while the body fights the infection using fever and other means. Other causes include:
  
  BULLET::::- Anxiety
  
  BULLET::::- Brain tumor
  
  BULLET::::- Chronic pains
  
  BULLET::::- Concussion – a mild traumatic brain injury
  
  BULLET::::- Diabetes
  
  BULLET::::- Fibromyalgia
  
  BULLET::::- Head injury
  
  BULLET::::- Hypercalcemia – too much calcium in the blood
  
  BULLET::::- Hypermagnesemia
  
  BULLET::::- Hyponatremia – low blood sodium
  
  BULLET::::- Hypothyroidism – the body doesn't produce enough hormones that control how cells use energy
   One solution to the issue of fatigue within sustained operations came when the United States Department of Defense (DoD) sought to find a way to identify and quantify potential danger zones related to fatigue. In 1996, the Walter Reed Army Institute of Research (WRAIR) began work on the Sleep Performance Model (SPM), in order to perform analysis related to sleep deprivation and its effects on human performance. It led to the development of the SAFTE (Sleep, Activity, Fatigue, and Task Effectiveness) model – a model which calculates effectiveness based on the human sleep/work cycle.
   When awake, our brainwaves are faster during the first half of the cycle, when we feel alert and focused, and then our brainwaves slow; in the last 20 minutes when we feel dreamy and perhaps a little tired, while our body is being readied for the alert part of the following cycle. 
   Section::::Timing.:Process S.
  
  Generally speaking, the longer an organism is awake, the more it feels a need to sleep ("sleep debt"). This driver of sleep is referred to as Process S. The balance between sleeping and waking is regulated by a process called homeostasis. Induced or perceived lack of sleep is called sleep deprivation.
  
  Process S is driven by the depletion of glycogen and accumulation of adenosine in the forebrain that disinhibits the ventrolateral preoptic nucleus, allowing for inhibition of the ascending reticular activating system.
   BULLET::::- report sleeping too much (subjective hypersomnia without objective findings)
  
  Section::::Symptoms and diagnosis.
  
  This sleep disorder frequently applies when patients report not feeling tired despite their subjective perception of not having slept. Generally, they may describe experiencing several years of no sleep, short sleep, or non-restorative sleep. Otherwise, patients appear healthy, both psychiatrically and medically. (That this condition is often asymptomatic could explain why it is relatively unreported.)
   It has also been shown that when slow-wave sleep was suppressed for three nights, young healthy subjects were 25% less sensitive to insulin. They needed more insulin to get rid of the same amount of glucose. If the body does not release more insulin to compensate, the blood-glucose levels will increase. This resembles impaired glucose tolerance, which can result in type 2 diabetes.
  
  Section::::Lack of Sleep Related to Weight Gain.
   Sleep loss is currently proposed to disturb endocrine regulation of energy homeostasis leading to weight gain and obesity. For instance, laboratory sleep deprivation studies in young men have demonstrated that one night of wakefulness (typically found in shift workers) exerts significant effects on the energy balance the next morning, including reduced energy expenditure, enhanced hedonic stimulus processing in the brain underlying the drive to consume food, and overeating that goes beyond satiety. Further recent studies have shown that a reduction of sleep duration to four hours for two consecutive nights has been shown to decrease circulating leptin levels and to increase ghrelin levels, as well as self-reported hunger. Similar endocrine alterations have been shown to occur even after a single night of sleep restriction.
   Second wind (sleep)
  
  Second wind (or third wind, fourth wind, etc.), also occasionally referred to as the wake maintenance zone, is a sleep phenomenon in which a person, after a prolonged period of staying awake, temporarily ceases to feel drowsy, often making it difficult to fall asleep once it happens. They are the result of circadian rhythms cycling into a phase of wakefulness. For example, many people experience the effects of a second wind in the early morning even after an entire night without sleep because it is the time when they would normally wake up.
   Section::::Causes.:Caffeine.
  
  A study from the University of Kentucky depicted that more than 78% of college freshmen consume above the recommended amount of caffeine each day. In one group of researchers' study from the Henry Ford Hospital's Sleep and Research Center and Wayne State College of Medicine, they discovered that caffeine consumed at least six hours before bedtime can significantly disrupt sleep. Participants in this study who consumed caffeine right before bedtime, three hours before bedtime, and six hours before bedtime all experienced a shorter night's sleep, lower sleep quality and spent more time awake at night.
  
  Section::::Causes.:Biology.
   Wakefulness
  
  Wakefulness is a daily recurring brain state and state of consciousness in which an individual is conscious and engages in coherent cognitive and behavioral responses to the external world. Being awake is the opposite of the state of being asleep in which most external inputs to the brain are excluded from neural processing.
  
  Section::::Effects upon the brain.
  
  The longer the brain has been awake, the greater the synchronous firing rates of cerebral cortex neurons. After sustained periods of sleep, both the speed and synchronicity of the neurons firing are shown to decrease.
  