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. Along with corresponding messages from the circadian clock, this tells the body it needs to sleep. 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 they were moderately sleep-deprived. Sleep duration is affected by the gene DEC2. Some people have a mutation of this gene; they sleep two hours less than normal. The human biological clock is illustrated below.
The biological clock is located within the
suprachiasmatic nucleus in the brain.
The entrainment of the biological clock. Black bars, asleep; gray bars, awake.
Hours by age
Children need more sleep per day in order to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages. A newborn baby spends almost 9 hours a day in REM sleep. By the age of five or so, only slightly over two hours is spent in REM. Studies say that school age children need about 10 to 11 hours of sleep.
Note: While some individuals claim full effectiveness with only 3-5 hours of sleep per night, some admit needing at least 8 hours of sleep per night (or more) to perform effectively. Hence, Sleep deprivation is best defined at this point by group means and in terms of the tasks impaired.
Siesta or nap
The siesta/nap habit has recently been associated with reduced cardiovascular stress meditated by daytime sleep. Epidemiological studies on the relations between cardiovascular health and siesta have led to conflicting conclusions, possibly because of poor control of moderator variables, such as the physical activity. It is possible that people who take a nap/siesta have different physical activity habits, e.g., waking earlier and scheduling more activity during the morning. Such differences in physical activity may mediate different 24-hour profiles in cardiovascular function. It was suggested that a short nap can reduce stress and blood pressure.
Sleep Debt and the effects of sleep deprivation
Sleep debt is the effect of not getting enough sleep; a large debt causes mental, emotional, and physical fatigue. Sleep debt results in diminished abilities to perform high-level cognitive functions. Neurophysiological and functional imaging studies have demonstrated that frontal regions of the brain are particularly responsive to homeostatic sleep pressure. Scientists do not agree on how much sleep debt it is possible to accumulate; whether it is accumulated against an individual’s average sleep or other things; nor on whether the prevalence of sleep debt among adults has changed in the industrialized world in recent decades. It is likely that children are sleeping less than previously in Western societies.
Studies have shown that individuals deprived of sleep after 24 hours of sustained wakefulness, the metabolic activity of the brain decreases significantly (up to 6% for the whole brain). In humans, sleep deprivation also results in a decrease in core body temperature, a decrease in immune system function as measured by white cell count and activity, and a decrease in the release of growth hormone. Sleep deprivation has also been implicated as a cause of increased heart rate variability.
With decreased sleep, high-order cognitive tasks are affected early and disproportionately. Tests requiring both speed and accuracy demonstrate considerably slower speed before accuracy begins to fail. 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 leads to impairment of cognitive work requiring simultaneous focus on several tasks. For example, in driving simulations accidents increase progressively as total sleep duration is decreased to 7, 5, and 3 hours per night over 1 week. In the same simulations, 3 hours total sleep duration was associated with loss of ability to simultaneously appreciate peripheral and centrally presented visual stimuli, which could be termed as a form of visual simultanagnosia and peripheral visual neglect.
In tasks requiring judgement, increasingly risky behaviours emerge as the total sleep duration is limited to 5 hours per night. The high cost of an action seemingly is ignored as the sleep-deprived individual focuses on limited benefit. Moreover, the areas most important for judgement, impulse control, attention, and visual association are disproportionately hypometabolic compared to the primary sensory and motor areas necessary for receiving and acting upon the environmental inputs. This theory leads to the hypothesis that the areas of the brain most responsible for higher-order cognition are to some degree less functional during sleep-deprived waking activity.
Other consequences of sleep deprivation are drowsy driving or workplace accidents or errors.
Personal Response:
In my humble opinion and as an individual who has experienced sequences of sleep deprivation particularly in my high school career, I believe that teachers and professors must consider the physical, emotional, and mental health of students who go to school. What I mean by this is by not giving out excessive amount of homework. Especially the students who work extremely hard, like me, sitting for hours every night studying and doing homework that must be done for the next day, we deserve to get the optimum amount of sleep of at least 8 hours. We are constantly sleep-deprived due to us being forced to stay up until late at night to do homework and then having to wake up early again. The fact that we go to school for 6-7 hours is one thing, however we should not have to constantly stay up late and interrupt our sleep time just to complete homework. Thus, I certainly think that my anxiety, stress, and inability to function at school is a result of me going to bed late and only getting between 5-6 hours of sleep on school nights. You do feel the symptoms of sleep deprivation and it is not a good feeling whatsoever. There is a big difference between getting at least 8 hours of sleep and less than 8 hours of sleep, you are able to function properly with adequate sleep and live your life to the best of your quality. A solution to this problem would be to definitely reduce the amount of homework, tests, projects that teachers give out in high school since there are indeed a lot of hard working students and especially in the stage of adolescence when our body is still growing and developing, we need adequate sleep for our muscles and skeleton to grow.
Genetics
It is suspected that a considerable amount of sleep-related behaviour, such as when and how long a person needs to sleep, is regulated by our genetics. Researchers have discovered some evidence that seems to support this assumption. ABCC9 is one gene found which influences the duration of human sleep.
Functions of sleep:
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Restoration: Wound healing has shown to be affected by sleep. Also sleep deprivation affects the immune system. Sleep loss impairs immune function and immune challenge alters sleep. It has also 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. Sleep has also been theorized to effectively combat the accumulation of free radicals in the brain, by increasing the efficiency of endogenous antioxidant mechanisms. An increase in sleep also affects growth hormone levels in adult men specifically. The higher amount of sleep time, the higher growth hormone secretion penetrated and vice versa.
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Ontogenesis: This hypothesis of REM sleep (active sleep) seems to be particularly important to the developing organism. Studies investigating the effects of sleep deprivation of active sleep have shown that deprivation early in life can result in behavioural problems, permanent sleep disruption, decreased brain mass, and an abnormal amount of neuronal cell death. REM sleep seems to be important for development of the brain and occupies the majority of sleep time of infants who spend most of their time sleeping.
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Memory processing: Scientists have shown numerous ways in which sleep is related to memory. Studies have shown that 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. There is an evident correlation between sleep and the complex functions of memory. Some researchers point out that an essential part of memory and learning consists of nerve cell dendrites’ sending of information to the cell body to be organized into new neuronal connections. This process demands that no external information is presented to these dendrites, and it is suggested that this may be why it is during sleep that memories and knowledge are solidified and organized.
Dreaming
Dreaming is the perceived experience of sensory images and sounds during sleep, in a sequence in which the dreamer usually perceives more as an apparent participant than an observer. Dreaming is stimulated by the pons and mostly occurs during the REM (active) phase of sleep.
Effect of food and drink on sleep:
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Hypnotics: Some people often drink alcohol in order to get to sleep, however being addicted to alcohol can actually lead to disrupted sleep because alcohol has a rebound affect later in the night and it can reduce REM sleep. Similarly, marijuana is used by some people to induce sleepiness however reduced REM sleep and usually affects people in the sense that they are not able to recall their dreams after excessive marijuana. Melatonin is a naturally occurring hormone that regulates sleepiness. It is made in the brain, where tryptophan is converted into serotonin and then into melatonin, which is released at night by the pineal gland to induce and maintain sleep. Melatonin supplementation may be used as a sleep aid.
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Stimulants: The stimulant of cocaine or crack cocaine is related to the onset of hypersomnia (oversleeping). Tobacco has been found not only to disrupt but also reduce total sleep time and hence more daytime drowsiness in smokers than in non-smokers.
Insomnia
Insomnia is a general term for 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 behavioural changes like keeping a regular and consistent sleep schedule, avoiding stimulating or stressful activities before bedtime, and cutting down on stimulants such as caffeine. Patients are often counselled 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. Some scientific research has suggested that exercise generally improves sleep for most people, and helps sleep disorders such as insomnia. The optimum time to exercise may be 4-8 hours before bedtime, though exercise at any time of the day is beneficial, with the exception of heavy exercise taken shortly before bedtime, which may actually disturb sleep.
Obstructive sleep apnea
Obstructive sleep apnea is a condition in which major pauses in breathing occur during sleep, disrupting the normal progression of sleep and often causing other more severe health problems. Apneas occur when the muscles around the patient’s airway relax during sleep, causing the airway to collapse and block the intake of oxygen. As oxygen levels drop in the blood drop, the patient then comes out of deep sleep in order to resume breathing. Major risk factors for sleep apnea include: chronic fatigue, old age, obesity, and snoring.
Somnambulism
Known as sleep walking, is a very common sleeping disorder, especially among children. In somnambulism, the individual gets up from his/her sleep and wanders around while still sleeping. Older people are more easily awakened by disturbances in the environment and may, to some degree, lose the ability to consolidate sleep.
Anthropology of sleep
Research suggests that sleep patterns vary significantly across cultures. The most striking differences are between societies that have plentiful sources of artificial light and ones that do not. The primary difference appears to be that pre-light cultures have more broken-up sleep patterns. For example, people might go to sleep far sooner after the sun sets, but then wake up several times throughout the night, punctuating their sleep with periods of wakefulness, perhaps lasting several hours. The boundaries between sleeping and waking are blurred in these societies. In addition, some observers believe that night time sleep in these societies is most often split into two main periods, the first characterized primarily by deep sleep and the second by REM sleep.
Some societies display a fragmented sleep pattern in which people sleep at all times of the day and night for shorter periods. In general, people sleep in a more concentrated burst through the night, going to sleep much later.
Comparison of Physiological Changes during NREM and REM sleep
The functions of many organ systems are also linked to the sleep cycle, as follows:
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Endocrine system. Most hormone secretion is controlled by the circadian clock or in response to physical events. Sleep is one of the events that modify the timing of secretion for certain hormones. Many hormones are secreted into the blood during sleep. For example, scientists believe that the release of growth hormone is related in part to repair processes that occur during sleep. Follicle stimulating hormone and luteinizing hormone, which are involved in maturational and reproductive processes, are among the hormones released during sleep. In fact, the sleep-dependent release of luteinizing hormone is thought to be the event that initiates puberty. Other hormones, such as thyroid-stimulating hormone, are released prior to sleep.
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Renal system. Kidney filtration, plasma flow, and the excretion of sodium, chloride, potassium, and calcium all are reduced during both NREM and REM sleep. These changes cause urine to be more concentrated during sleep.
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Alimentary activity. In a person with normal digestive function, gastric acid secretion is reduced during sleep. In those with an active ulcer, gastric acid secretion is actually increased and swallowing occurs less frequently.
Pathways of brain activity during REM sleep. Body temperature in relation to the sleep cycle.
Homeostatic regulation of sleep: the pressure to Areas of the brain active during REM
sleep grows stronger across the day as one stays sleep dreaming.
awake and then dissipates when one sleeps at
night (shaded area). Sleep pressure increases
(dashed line) as one stays awake longer into the
normal sleeping hours.
Fact Sheet about sleep
- Problems with sleepiness may be associated with difficulty concentrating, memory lapses, loss of energy, fatigue, lethargy, and emotional instability.
- Anything less than five minutes to fall asleep at night means you’re sleep deprived. The ideal is between 10 to 15 minutes, meaning you are still tired enough to sleep deeply, but not so exhausted you sleepy by day.
- It is impossible to tell if someone is really awake without close medical supervision. People can take naps or sleep with their eyes open without being aware of it.
- Experts say that one of the most alluring sleep distractions is the 24-hour accessibility of the internet.
- The average person spends 6 years of their life dreaming during sleep.
- When you die, you will have slept for about 1/3 of your life, which for the average person is approximately 25 years.
- The average person wakes up about 6 times per night.
- You can only dream about faces you have already seen.
- Sleep positions may determine your personality.
- You can die from sleep deprivation before food deprivation. It takes 2 weeks to starve, but 10 days without sleep can kill you.
- Within 5 minutes of waking up, 50% of your dream is forgotten. Within 10 minutes, 90% is gone.
- Lack of sleep can raise the sensation of hunger by 25%.
- Studies show that regularly sleeping too little (6 hours or less) or regularly sleeping too much (more than 9 hours) is associated with a shorter lifespan (but depends on age).
- Sleeping directly after learning something new will improve your ability to remember it effectively.
- New parents lose out a total of 6 months’ sleep in the first two years of childcare.
- The biological clock that times and controls a person’s sleep/wake cycle will attempt to function according to a normal day/night schedule even when that person tries to change it.
- Sleep walking, sleep talking, and sleep terrors are more common in children than adults. Children generally have no memory of such events, usually do not require treatment, and usually outgrow the disorder.
- Some scientists believe we dream to fix experiences in long-term memory, that is, we dream about things worth remembering. Others think we dream about thinks worth forgetting-to eliminate overlapping memories that would otherwise clog up our brains.
- On average, humans in general sleep for 3 hours less than other primates like chimps and baboons.
Average sleep need (left graph) and percentage of REM sleep (right graph) at different ages.
Personal Response:
Very few textbooks for high school students provide any scientific information about changes that occur in the body during sleep and how those changes affect our ability to move and think. Of course, we’ve heard that a good night’s sleep will help us perform better on a test the next day, but is this based on scientific fact, or is it just a continuing myth? The lack of information in textbooks may be due to the fact that sleep research is only recently gaining recognition. A great deal remains to be learned through scientific studies, including an answer to the key question, what is the true function of sleep? Although its function remains somewhat unclear, research is providing a great deal of information about what happens in the brain and body during sleep and how the body regulates sleep.
Misconceptions about sleep
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Misconception 1: Sleep is time for the body in general and the brain specifically to shut down for rest.
- Sleep is in active process involving specific cues for its regulation. Although there are some modest decreases in metabolic rate, there is no evidence that any major organ or regulatory system in the body shuts down during sleep. Some brain activity, including delta waves, increases dramatically. Also, the endocrine system increases secretion of certain hormones, such as growth and prolactin (as mentioned earlier). In REM sleep, many parts of the brain are as active as at any time when awake.
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Misconception 2: Getting just one hour less sleep per night than needed will not have any effect on daytime functioning.
- When daily sleep time is less than an individual’s needs, a “sleep debt” develops. Even relatively modest daily reductions in sleep time (one hour) can accumulate across days to cause a sleep debt. If the debt becomes too great, it can lead to sleepiness problems. Although the individual may not realize his or her sleepiness, the sleep debt can have powerful effects on daytime performance, thinking, and mood.
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Misconception 3: The body adjusts quickly to different sleep schedules.
- The biological clock that times and controls a person’s sleep/wake cycle will attempt to function according to a normal day/night schedule even when that person tries to change it. Those who work nightshifts naturally feel sleepy when night time comes. A similar feeling that occurs during travel is jetlag. This conflict, set up by trying to be active during the brain’s biological night time, leads to a decrease in cognitive and motor skills. The biological clock can be reset, but only by appropriately timed cues, and even then, by one to two hours per day at best. Problems resulting from a mismatch of this type may be reduced by behaviours such as sleeping in a dark, quiet room, getting exposure to bright light at the right time, and altering eating and exercising patterns. Because humans function best when they sleep at night and act in the daytime.
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Misconception 4: People need less sleep as they grow older.
- Older people don’t need less sleep, but they often get less sleep. That’s because the ability to sleep for long periods of time and to get into the deep, restful stages of sleep decreases with age. Many older people have more fragile sleep and are more easily disturbed by light, noise, and pain than when younger. They are also more likely to have medical conditions that contribute to sleep problems.
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Misconception 5: A “good night’s sleep” can cure problems with excessive daytime sleepiness.
- Excessive daytime sleepiness can be associated with a sleep disorder or other medical condition. Sleep disorders, including sleep apnea (as mentioned earlier), insomnia, and narcolepsy, may require behavioural, pharmacological, or even surgical intervention to relieve the symptoms. Extra sleep may not eliminate daytime sleepiness that may be due to such disorders.
A typical hypnogram from a young, healthy adult. Light-gray areas represent non–rapid eye movement (NREM) sleep.
Media File
This article is about the interrelationship among teens, sleep, and school. Basically the article talks about how research has shown that teenagers don’t get enough sleep at night and go to school tired, something I have noticed myself too. Some proposed causes of it have been biological and other potential causes are that teens stay up late because of adolescent distractions. Early high school start times also contribute to teens’ tiredness.
In this article, it is noted that teenagers need minimum 8-9 hours of sleep and that more than 50% of North American teenagers are chronically sleep-deprived and accumulating many hours of sleep deficit which is causing concern for many parents, researchers, and educators.
So why aren’t teens getting enough sleep? The number one reason is because they are staying up late as a result of a variety of things including social life, caffeinated drinks, electronic media (computers, TVs, cell phones. In addition, other stated factors involve some teens procrastinating on homework, and even depression. The adolescents who work and have jobs as well get less sleep. Some of the biological aspects that experts have mentioned were that puberty stages in teens prevent teens from being able to fall asleep as early as when they were younger. The measure of the sleep-promoting hormone melatonin levels rise later at night than they do in children and adults and remain at a higher level later in the morning.
Lack of sleep definitely affects teen’s ability to function at school. It can affect mood, performance, attention, learning, behaviour, and biological functions. It can sometimes be hard to stay awake and concentrate in class and minimal sleep can contribute to mood swings and behavioural problems.
So clearly the solutions to these problems are for parents to impose earlier bedtimes on their teenagers and by discouraging them from drinking caffeine past 12 noon, and by keeping all electronics out of their room at night.
Tips for a good night’s sleep:
- Encourage a short nap (30 minutes) after school with the alarm clock set
- Encourage a regular bedtime routine to help them unwind
- Dim the lights as bedtime approaches
- Encourage your teen to go to bed and get up at the same time every school day
- Cut out late-night phone or internet chats
- Avoid arguing with your teen just before bedtime-may contribute to teen depression
- Pull open the curtains and let sun shine in, or turn on the bright lights in the morning
- Help kids understand that they need more sleep because of changes in their bodies
- Let them sleep on the weekend, but no more than 2 or 3 hours later than their usual time, or it will disrupt their body clock
- Exercise 20-30 minutes a day at least 5-6 hours before going to bed
- Avoid caffeine, nicotine, and alcohol which act as stimulants and keep people awake and can rob people of deep sleep and REM sleep while keeping them in the lighter stages of sleep
- Relax before bed: a warm bath, reading, or any relaxation activity can make it easier to fall asleep
- Sleep until sunlight: if possible, wake up with the sun, or use very bright lights in the morning-sunlight helps the body’s internal biological clock reset itself each day; and there is a recommendation of 1 hour of exposure to morning sunlight
- Don’t lie in bed awake: if you can’t sleep don’t just lie in bed, do something else like reading, watching television, or listening to music until you feel tired again. The anxiety of unable to fall asleep can actually contribute to insomnia
- Control your room temperature: maintain a comfortable temperature in the bedroom. Extreme temperatures may disrupt sleep or prevent you from falling asleep
- See a doctor if your sleeping problem continues: If you have trouble falling asleep night after night or if you always feel tired the next day then you may have a sleep disorder and should see a physician whom may be able to help treat it and give you a good night sleep
Note: Some parents may find it difficult to take these suggestions without imposing more rules on their teens' daily life. Discussing the importance of sleep with teens will make it easier. Since all teens are not the same, parents should use their parenting experience to best help their teens with sleep.
This article explains the relation between daylight-saving time and sleep. The implications of this article are that in the springtime, the switch from standard to daylight-saving time is merely an inconvenience for the simple reason that we are all losing one hour of sleep by moving are clocks one hour forward. Sometimes this can cause problems of adjustment if we have appointments because it may cause some people to miss their appointment at a scheduled time. For other people, this change in time can mean more sleepiness and reduced concentration as it damages people’s sleep. In fact, researchers have proposed tips for daylight-saving times in the spring:
- Reset all your clocks on the Saturday before the switch
- Get a full night’s sleep during the switch
- Follow your conventional bedtime to ensure you get a full goodnight’s sleep-meaning you are getting up one hour earlier, so it is imperative to go to bed one hour earlier
- Resist the temptation to catch a nap in the middle of the day on Sunday, it can disrupt your biological clock
Some researchers indicate that the switch on daylight-saving times begins to initiate bad sleeping habits which relates to what was discussed earlier.
This article is about the significance of healthy sleep habits and the affect on the neurology of the brain of humans. Healthy sleep habits do more than just keep you alert- they can also keep you healthier. Getting more sleep might even make you a better employee or student. These healthy sleep habits generally allow people to wake up feeling refreshed, think quickly, successfully perform potentially dangerous tasks such as driving, which requires complete attention, and do your very best at work or school.
The dangers of ignoring healthy sleep habits relate to sleep deprivation in many ways. It can lead to cardiovascular dysfunction, lowered immune system response, glucose and insulin abnormalities (diabetes) deregulation of hormones which control appetite, and impaired cognitive function. The implications are serious as bad sleep habits can cause mental impairments to accidents. Other causes of bad sleeping habits/deprivation researchers have hypothesized are: loss of energy and feelings of exhaustion, anxiety, depression or irritability, memory problems, trouble paying attention, delayed reactions, and reduced ability to learn (particularly at school), and impaired ability to think fast and avoid mistakes or accidents, and perhaps a limited ability to multitask. Kids are more vulnerable to sleep disruptions because their bodies are still developing and they are of a young age, so precautions must be taken.
Works Cited-Bibliography
Australian Broadcasting Corporation . "The National Sleep Research Project - 40
amazing facts about sleep." ABC.net.au. The National Sleep Research Project, n.d. Web. 30 Dec. 2012. <http://www.abc.net.au/science/sleep/facts.htm
"Chapter Summary of Sleep ." Sleep Physiology . NCBI and National Academy of Sciences, n.d. Web. 30 Dec. 2012. <www.ncbi.nlm.nih.gov/books/NBK19956/>.
"Sleep." MedicineNet.com-We bring doctor's knowledge to you. MedicineNet , n.d. Web. 30 Dec. 2012. <www.medicinenet.com/sleep/article.htm>.
"Sleep - Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia. Wikipedia, n.d. Web. 30 Dec. 2012. <http://en.wikipedia.org/wiki/Sleep>.
Stevens, M Suzanne. "Normal Sleep, Sleep Physiology, and Sleep
Deprivation." Medscape: Medscape Access-Drugs, Diseases, and Proceures. Medscape
Reference, n.d. Web. 30 Dec. 2012. <http://emedicine.medscape.com/article/1188226-overview#showall>.
"Teacher's Guide: Information about sleep." Sleep, Sleep Disorders, and Biological
Rhythms . National Institute of Health-Sleep , n.d. Web. 30 Dec. 2012. <science.education.nih.gov/supplements/nih3/sleep/guide/info-sleep.htm>.
by
cherno (student)
