Ignore this post if you want to because it is going to be a super long and factual post. I just find that recently people have been havig insufficient sleep and complaining of havin short term memory. Its inter-linked if you haven realised...
Now the detailed informations...
Adapted from: http://www.emedicinehealth.com/sleep_understanding_the_basics/article_em.htm
(read only the red words if you don wan to read everything)
Sleep
Sleep is defined as a state of unconsciousness from which a person can be aroused. In this state, the brain is relatively more responsive to internal stimuli than external stimuli. Sleep should be distinguished from coma. Coma is an unconscious state from which a person cannot be aroused. Sleep is essential for the normal, healthy functioning of the human body. It is a complicated physiological phenomenon that scientists do not fully understand.
Historically, sleep was thought to be a passive state. However, sleep is now known to be a dynamic process, and our brains are active during sleep. Sleep affects our physical and
States of brain activity during sleep and wakefulness result from different activating and inhibiting forces that are generated within the brain. Neurotransmitters (chemicals involved in nerve signaling) control whether one is asleep or awake by acting on nerve cells (neurons) in different parts of the brain. Neurons located in the brainstem actively cause sleep by inhibiting other parts of the brain that keep a person awake.
Importance of Sleep
Animal studies have shown that sleep is necessary for survival. The normal life span of rats is 2-3 years. However, rats deprived of sleep live for only about 3 weeks. They also develop abnormally low body temperatures and sores on their tails and paws. The sores probably develop because of impairment of the rats’ immune systems.
In humans, it has been demonstrated that the metabolic activity of the brain decreases significantly after 24 hours of sustained wakefulness. Sleep deprivation results in a decrease in body temperature, a decrease in immune system function as measured by white blood cell count (the soldiers of the body), and a decrease in the release of growth hormone. Sleep deprivation can also cause increased heart rate variability.
For our nervous systems to work properly, sleep is needed. Sleep deprivation makes a person drowsy and unable to concentrate the next day. It also leads to impairment of memory and physical performance and reduced ability to carry out mathematical calculations. If sleep deprivation continues, hallucinations and mood swings may develop.
Release of growth hormone in children and young adults takes place during deep sleep. Most cells of the body show increased production and reduced breakdown of proteins during deep sleep. Sleep helps humans maintain optimal emotional and social functioning while we are awake by giving rest during sleep to the parts of the brain that control emotions and social interactions.
Stages of Sleep
As mentioned earlier, sleep is a dynamic process. There are 2 distinct states that alternate in cycles and reflect differing levels of neuronal activity. Each state is characterized by a different type of brain wave (electrical activity that is recorded with the help of electrodes placed on the skull) activity. Sleep consists of non–rapid eye movement (NREM) and rapid eye movement (REM) sleep. NREM is further subdivided into the following 4 stages:
NREM Sleep
Stage I is a stage of light sleep and is considered a transition between wakefulness and sleep. During this stage, the muscles begin to relax. It occurs upon falling asleep and during brief arousal periods within sleep, and usually accounts for 5-10% of total sleep time. An individual can be easily awakened during this stage.
REM Sleep
REM sleep represents 20-25% of the total sleep time. REM sleep follows NREM sleep and occurs 4-5 times during a normal 8- to 9-hour sleep period. The first REM period of the night may be less than 10 minutes in duration, while the last may exceed 60 minutes. In a normal night’s sleep, bouts of REM occur every 90 minutes.
When the person is extremely sleepy, the duration of each bout of REM sleep is very short or it may even be absent. REM sleep is usually associated with dreaming. During REM sleep, the eyeballs move rapidly, the heart rate and breathing become rapid and irregular, and the blood pressure rises. The muscles of the body are virtually paralyzed. The brain is highly active during REM sleep, and the overall brain metabolism may be increased by as much as 20%. The electrical activity recorded in the brain during REM sleep is similar to that which is recorded during wakefulness.
Sleep at Different Stages of Life
Infancy
Infants have an overall greater total sleep time than any other age group. Their sleep time can be divided into multiple periods. In newborns, the total sleep duration in a day can be 14-16 hours. Over the first several months of life, sleep time decreases; by age 5-6 months, sleep consolidates into an overnight period with at least 1 nap during the day.
REM sleep in infants represents a larger percentage of the total sleep at the expense of stages III and IV. Until age 3-4 months, newborns transition from wakefulness into REM sleep. Thereafter, wakefulness begins to transition directly into NREM sleep.
Adulthood
In adults, sleep of 8-8.4 hours is considered fully restorative. In some cultures, total sleep is often divided into an overnight sleep period of 6-7 hours and a nap of 1-2 hours.
Some people may need as little as 5 hours or as much as 10 hours of sleep every day. The period of time a person sleeps depends also on the fact whether he or she has been deprived of sleep in previous days. Sleeping too little creates a "sleep debt." This debt needs to be adjusted by sleeping for longer periods over the next few days. People who sleep less have an impairment of judgment and reaction time.
Time taken to fall asleep and the number and duration of overnight arousal periods increase. Thus, to have a fully restorative sleep, the total time in bed must increase. If the elderly person does not increase the total time in bed, complaints of insomnia and chronic sleepiness may occur.
Sleep fragmentation results from the increase in overnight arousals and may be exacerbated by the increasing number of medical conditions related to old age, including
Circadian Rhythms That Influence Sleep
Biological variations that occur in the course of 24 hours are called circadian rhythms. Circadian rhythms are controlled by the body’s biological clock. Many bodily functions follow the biologic clock, but sleep and wakefulness comprise the most important circadian rhythm. Circadian sleep rhythm is one of the several body rhythms modulated by the hypothalamus (a part of the brain).
Melatonin (a chemical produced by the pineal gland in the brain) has been implicated as a modulator of light entrainment. It is secreted maximally during the night. Prolactin, testosterone, and growth hormone also demonstrate circadian rhythms, with maximal secretion during the night.
Circadian rhythms can be affected to a certain degree by almost any kind of external stimulus
Symptoms similar to those seen in people with jet lag are common in people who work during nights or work in shifts. Because these people’s wake time conflicts with powerful sleep-regulating cues like sunlight, they often become uncontrollably drowsy during work or may have difficulty falling asleep during their off time. Their biological clock wants to do one thing, while they are doing something entirely different. People working in shifts have an increased risk of heart, gastrointestinal, emotional, and mental problems. All these problems may be related to the disruption of the circadian sleep rhythm.
Substances That Alter Sleep
People who smoke heavily often sleep very lightly and have reduced duration of REM sleep. Heavy smokers tend to wake up after 3 or 4 hours of sleep due to nicotine withdrawal. Some people who have insomnia may use alcohol. Even though alcohol may help people to fall into light sleep, it deprives them of REM sleep and the deeper and more restorative stages of sleep. Instead, it keeps them in the lighter stages of sleep from which they can be awakened easily.
During REM sleep, we lose some of our ability to regulate our body temperature. Therefore, abnormally hot or cold temperatures can disrupt our REM sleep. If our REM sleep is disturbed, the normal sleep cycle progression is affected during the next sleeping time, and there is a possibility of slipping directly into REM sleep and going through long periods of REM sleep until the duration of REM sleep that is lost is caught up.
Sleep Deprivation
Because the function of sleep has not been fully determined, the exact number of hours that a person should sleep is unknown. Some persons claim to work optimally with only 3-5 hours of sleep per night, while some admit needing at least 8 hours of sleep per night (or more) to perform effectively. Therefore, sleep deprivation is best defined by group means and in terms of the tasks impaired.
In tasks requiring judgment, increasingly risky behaviors emerge as the total sleep duration is limited to 5 hours per night. The high cost of an action is seemingly ignored as the sleep-deprived person focuses on limited benefits. These findings can be explained by the fact that metabolism in the prefrontal and parietal associational areas of the brain decrease in individuals deprived of sleep for 24 hours. These areas of the brain are important for judgment, impulse control, attention, and visual association.
Sleep deprivation is a relative concept. Small amounts of sleep loss (for example, 1 hour per night over many nights) produce subtle cognitive impairment, which may go unrecognized. More severe restriction of sleep for a week leads to profound cognitive deficits, which may also go unrecognized by the individual. If you feel drowsy during the day, fall asleep for very short periods of time (5 minutes or so), or regularly fall asleep immediately after lying down, you are probably sleep-deprived.
Many studies have made it clear that sleep deprivation is dangerous. With decreased sleep, higher-order cognitive tasks are impaired early and disproportionately. On tasks used for testing coordination, sleep-deprived people perform as poorly as or worse than people who are intoxicated. Total sleep duration of 7 hours per night over 1 week has resulted in decreased speed in tasks of both simple reaction time and more demanding computer-generated mathematical problem solving. Total sleep duration of 5 hours per night over 1 week shows both a decrease in speed and the beginning of accuracy failure.
Total sleep duration of 7 hours per night over 1 week leads to impairment of cognitive work requiring simultaneous focus on several tasks. In driving simulations, for example, accidents increase progressively as total sleep duration is decreased to 7, 5, and 3 hours per night over 1 week. Driver fatigue is responsible for an estimated 100,000 motor vehicle crashes and 1500 deaths each year, according to the National Highway Traffic Safety Administration.
Since drowsiness occurs just before falling asleep, driving while drowsy often leads to disaster. According to the National Sleep Foundation “If you have trouble keeping your eyes focused, if you can’t stop yawning, or if you can’t remember driving the last few miles, you are probably too drowsy to drive safely.” It is important to know that caffeine and other stimulants cannot overcome the effects of severe sleep deprivation
. Therefore, if you find yourself driving in a sleep-deprived state, it is imperative that you find a safe place to stop and catch up on your sleep before continuing safely on your way.