Relaxologie niveau 1 Base. Lizards suffering from severe hypocalcemia and hyperphosphatemia may exhibit periodic tremors and muscle fasciculations. Why is it that just certain areas in particular armpits, backbone, breastbone and groin have less bulky white fat and sweat more? Different species from different locations must not be mixed. The Sunday Telegraph, Jan 22, p Previous theory held that dietary deficiency is extremely rare unless the small intestine was heavily damaged, resulting in malabsorption of the molecule.
Menu de navigation
Nutrition in bacteria These small organisms, popularly thought of only as sources of infection, are of vital importance in the overall life cycles of plants and animals. Nutrition in animals Simple observation reveals that the animal kingdom is dependent on plants for food.
Page 2 of 5. Learn More in these related Britannica articles: Plant nutrition includes the nutrients necessary for the growth, maintenance, and reproduction of individual plants; the mechanisms by which plants acquire such nutrients; and the structural, physiological, and biochemical roles those nutrients play in metabolism.
Regulation of fertility level and nutrient balance. Potash and nitrogen, and the balance between the two, may affect the incidence of certain bacterial, fungal, and viral diseases of corn, cotton, tobacco, and sugar beet. A number of microelements, including…. Puppies need three basic things in order to thrive: Puppies need to eat three or four times a day from the time they are weaned until they are about six months old.
Thereafter they can be fed…. Nutrition involves balance between feeding habits of larval and adult flies. Primary feeding occurs during the larval stage. Adult feeding serves to compensate the shortcomings of larval nourishment. At one extreme are nonbiting midges, with larvae that vigorously filter microorganisms from water. For stabled horses, the diet generally consists of hay and grain.
The animal should not be fed immediately before or after work, to avoid digestive problems. Fresh water is important, especially when the horse is shedding its winter…. Animal sciences animal feed In feed dogs In dog: Nutrition and growth feeding behaviour In human sensory reception: Food choice higher animals In feeding behaviour: Nutritional requirements of higher animals horses In horse: Nutrition insects In insect: Digestive system In dipteran: Nutritional requirements View More.
Help us improve this article! Contact our editors with your feedback. Introduction Nutritional patterns in the living world Nutrition in plants Nutrition in bacteria Nutrition in animals Herbivores Carnivores Omnivores Nutrients Inorganic nutrients Organic nutrients Carbohydrates Lipids fats and oils Proteins Vitamins Interdependency of nutritional requirements Competition for sites of absorption by the cell Competition for sites of utilization within the cell Precursor-product relationships Changes in metabolic pathways within the cell Syntrophism Nutritional evolution of organisms.
You may find it helpful to search within the site to see how similar or related subjects are covered. Any text you add should be original, not copied from other sources. At the bottom of the article, feel free to list any sources that support your changes, so that we can fully understand their context.
Internet URLs are the best. Thank You for Your Contribution! There was a problem with your submission. Please try again later. Keep Exploring Britannica Cancer. Cancer, group of more than distinct diseases characterized by the uncontrolled growth of abnormal….
Bird, class Aves , any of the more than 10, living species unique in having feathers, the major characteristic…. Photosynthesis, the process by which green plants and certain other organisms transform light energy…. View All Media 3 Images. If you prefer to suggest your own revision of the article, you can go to edit mode requires login.
There is disagreement on how much sleep debt it is possible to accumulate, and whether sleep debt is accumulated against an individual's average sleep or some other benchmark.
It is also unclear whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades.
Sleep debt does show some evidence of being cumulative. Subjectively, however, humans seem to reach maximum sleepiness after 30 hours of waking. 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.
Humans are also influenced by aspects of social time , such as the hours when other people are awake, the hours when work is required, the time on the clock, etc. Time zones , standard times used to unify the timing for people in the same area, correspond only approximately to the natural rising and setting of the sun.
In polyphasic sleep , an organism sleeps several times in a hour cycle. Monophasic sleep occurs all at once. Under experimental conditions, humans tend to alternate more frequently between sleep and wakefulness i. Bimodal sleep in humans was more common before the industrial revolution. Different characteristic sleep patterns, such as the familiarly so-called " early bird " and " night owl ", are called chronotypes.
Genetics and sex have some influence on chronotype, but so do habits. Chronotype is also liable to change over the course of a person's lifetime. Seven-year-olds are better disposed to wake up early in the morning than are fifteen-year-olds.
Many people experience a temporary drop in alertness in the early afternoon, commonly known as the "post-lunch dip". While a large meal can make a person feel sleepy, the post-lunch dip is mostly an effect of the circadian clock.
People naturally feel most sleepy at two times of the day about 12 hours apart—for example, at 2: At those two times, the body clock "kicks in. At about 2 a. It is hypothesized that a considerable amount of sleep-related behavior, such as when and how long a person needs to sleep, is regulated by genetics.
Researchers have discovered some evidence that seems to support this assumption. Neurotransmitters, molecules whose production can be traced to specific genes, are one genetic influence on sleep which can be analyzed. And the circadian clock has its own set of genes. The quality of sleep may be evaluated from an objective and a subjective point of view.
Objective sleep quality refers to how difficult it is for a person to fall asleep and remain in a sleeping state, and how many times they wake up during a single night. Poor sleep quality disrupts the cycle of transition between the different stages of sleep. A study by A. 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. The timing is correct when the following two circadian markers occur after the middle of the sleep episode and before awakening: Human sleep needs vary by age and amongst individuals, and sleep is considered to be adequate when there is no daytime sleepiness or dysfunction.
Moreover, self-reported sleep duration is only moderately correlated with actual sleep time as measured by actigraphy ,  and those affected with sleep state misperception may typically report having slept only four hours despite having slept a full eight hours. Researchers have found that sleeping 6—7 hours each night correlates with longevity and cardiac health in humans, though many underlying factors may be involved in the causality behind this relationship.
Sleep difficulties are furthermore associated with psychiatric disorders such as depression , alcoholism , and bipolar disorder. Dysregulation detected by 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.
By the time infants reach the age of two, their brain size has reached 90 percent of an adult-sized brain;  a majority of this brain growth has occurred during the period of life with the highest rate of sleep. The hours that children spend asleep influence their ability to perform on cognitive tasks. Sleep also influences language development. To test this, researchers taught infants a faux language and observed their recollection of the rules for that language.
There is also a relationship between infants' vocabulary and sleeping: Children need many hours of sleep per day in order to develop and function properly: The human organism physically restores itself during sleep, healing itself and removing metabolic wastes which build up during periods of activity.
This restoration takes place mostly during slow-wave sleep , during which body temperature, heart rate, and brain oxygen consumption decrease. The brain, especially, requires sleep for restoration, whereas in the rest of the body these processes can take place during quiescent waking.
In both cases, the reduced rate of metabolism enables countervailing restorative processes. While awake, metabolism generates reactive oxygen species, which are damaging to cells. In sleep, metabolic rates decrease and reactive oxygen species generation is reduced allowing restorative processes to take over. The sleeping brain has been shown to remove metabolic waste products at a faster rate than during an awake state.
Sleep has also been theorized to effectively combat the accumulation of free radicals in the brain, by increasing the efficiency of endogenous antioxidant mechanisms. Studies suggest that sleep deprivation may impair the body's ability to heal wounds.
It has been shown that sleep deprivation affects the immune system. The effect of sleep duration on somatic growth is not completely known. One study recorded growth, height, and weight, as correlated to parent-reported time in bed in children over a period of nine years age 1— It was found that "the variation of sleep duration among children does not seem to have an effect on growth.
Sleep enhances memory ,   with procedural memory benefiting from late, REM-rich sleep, and explicit memory benefiting from early, slow wave-rich sleep. During sleep, especially REM sleep, people tend to have dreams: Dreams can seamlessly incorporate elements within a person's mind that would not normally go together. They can include apparent sensations of all types, especially vision and movement.
People have proposed many hypotheses about the functions of dreaming. Sigmund Freud postulated that dreams are the symbolic expression of frustrated desires that have been relegated to the unconscious mind , and he used dream interpretation in the form of psychoanalysis in attempting to uncover these desires. Counterintuitively, penile erections during sleep are not more frequent during sexual dreams than during other dreams.
Neatly, this theory helps explain the irrationality of the mind during REM periods, as, according to this theory, the forebrain then creates a story in an attempt to reconcile and make sense of the nonsensical sensory information presented to it. This would explain the odd nature of many dreams. Using antidepressants , [ clarification needed ] acetaminophen , ibuprofen , or alcoholic beverages is thought to potentially suppress dreams, whereas melatonin may have the ability to encourage them.
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. The sleep environment may be improved by installing heavy drapes to shut out all sunlight, and keeping computers, televisions and work materials out of the sleeping area. A review of published scientific research suggested that exercise generally improves sleep for most people, and helps sleep disorders such as insomnia.
The optimum time to exercise may be 4 to 8 hours before bedtime, though exercise at any time of day is beneficial, with the exception of heavy exercise taken shortly before bedtime, which may disturb sleep. However, there is insufficient evidence to draw detailed conclusions about the relationship between exercise and sleep. Although these nonbenzodiazepine medications are generally believed to be better and safer than earlier generations of sedatives, they have still generated some controversy and discussion regarding side-effects.
White noise appears to be a promising treatment for insomnia. 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.
When several of these episodes occur per hour, sleep apnea rises to a level of seriousness that may require treatment. Diagnosing sleep apnea usually requires a professional sleep study performed in a sleep clinic, because the episodes of wakefulness caused by the disorder are extremely brief and patients usually do not remember experiencing them.
Instead, many patients simply feel tired after getting several hours of sleep and have no idea why. Major risk factors for sleep apnea include chronic fatigue, old age, obesity and snoring. Fatal familial insomnia , or FFI, an extremely rare genetic disease with no known treatment or cure, is characterized by increasing insomnia as one of its symptoms; ultimately sufferers of the disease stop sleeping entirely, before dying of the disease. Somnambulism, known as sleep walking, is also a common sleeping disorder, especially among children.
Older people may be more easily awakened by disturbances in the environment  and may to some degree lose the ability to consolidate sleep. Drugs which induce sleep, known as hypnotics , include benzodiazepines , although these interfere with REM;  Nonbenzodiazepine hypnotics such as eszopiclone Lunesta , zaleplon Sonata , and zolpidem Ambien ; Antihistamines , such as diphenhydramine Benadryl and doxylamine ; Alcohol ethanol , despite its rebound effect later in the night and interference with REM;   barbiturates , which have the same problem; melatonin , a component of the circadian clock, and released naturally at night by the pineal gland ;  and cannabis , which may also interfere with REM.
Stimulants , which inhibit sleep, include caffeine , an adenosine antagonist; amphetamine , MDMA , empathogen-entactogens , and related drugs; cocaine , which can alter the circadian rhythm,   and methylphenidate , which acts similarly; and other analeptic drugs like modafinil and armodafinil with poorly understood mechanisms. Dietary and nutritional choices may affect sleep duration and quality. One review indicated that a high carbohydrate diet promoted shorter onset to sleep and longer duration sleep than a high fat diet.
Research suggests that sleep patterns vary significantly across cultures. The boundaries between sleeping and waking are blurred in these societies. Some societies display a fragmented sleep pattern in which people sleep at all times of the day and night for shorter periods.
In many nomadic or hunter-gatherer societies, people will sleep on and off throughout the day or night depending on what is happening. Roger Ekirch thinks that the traditional pattern of " segmented sleep ," as it is called, began to disappear among the urban upper class in Europe in the late 17th century and the change spread over the next years; by the s "the idea of a first and second sleep had receded entirely from our social consciousness.
In some societies, people sleep with at least one other person sometimes many or with animals. In other cultures, people rarely sleep with anyone except for an intimate partner. In almost all societies, sleeping partners are strongly regulated by social standards.
For example, a person might only sleep with the immediate family , the extended family , a spouse or romantic partner, children, children of a certain age, children of specific gender, peers of a certain gender, friends, peers of equal social rank, or with no one at all. Sleep may be an actively social time, depending on the sleep groupings, with no constraints on noise or activity.
People sleep in a variety of locations. Some sleep directly on the ground; others on a skin or blanket; others sleep on platforms or beds. Some sleep with blankets, some with pillows, some with simple headrests, some with no head support. These choices are shaped by a variety of factors, such as climate, protection from predators, housing type, technology, personal preference, and the incidence of pests.
Sleep has been seen in culture as similar to death since antiquity;  in Greek mythology , Hypnos the god of sleep and Thanatos the god of death were both said to be the children of Nyx the goddess of night. Many cultural stories have been told about people falling asleep for extended periods of time.
A far more famous instance of a "long sleep" today is the Christian legend of the Seven Sleepers of Ephesus ,  in which seven Christians flee into a cave during pagan times in order to escape persecution ,  but fall asleep and wake up years later to discover, to their astonishment, that the Roman Empire is now predominately Christian.
Writing about the thematical representations of sleep in art, physician and sleep researcher Meir Kryger noted: The Sentry by Carel Fabritius. Diana and Endymion c. Lullaby by William-Adolphe Bouguereau. Victory of Faith by Saint George Hare. Zwei schlafende Mädchen auf der Ofenbank Albert Anker. From Wikipedia, the free encyclopedia. This article is about sleep in humans. For non-human sleep, see Sleep non-human. For other uses, see Sleep disambiguation. For other uses, see Waking up disambiguation.
Wakefulness and Ascending reticular activating system. Circadian rhythm sleep disorder. Sleep and learning , Sleep and creativity , and Sleep and memory. This section needs expansion. You can help by adding to it. Taking a Rest by Ilya Repin. Sleeping Jaguar , by Paul Klimsch. Retrieved 24 May Retrieved 25 January How the lightbulb disrupted our sleeping patterns and changed the world".
Retrieved 31 August Journal of Clinical Sleep Medicine. Journal of Physiological Anthropology. Trading Sleep for Leno and Letterman". National Center for Biotechnology Information, U. National Library of Medicine. Journal of Biological Rhythms. American Journal of Physiology. L; Roth, Thomas 24 January Basic Science and Clinical Implications". Journal of Sleep Research. Thus, the shift in the evening bedtime across cohorts accounted for the substantial decrease in sleep duration in younger children between the s and the s Adenosine receptors in neurology and psychiatry.
International Review of Neurobiology. Molecules that build up and make you sleep". A systematic review of epidemiological studies and randomized controlled trials". Archived from the original PDF: Retrieved 5 June Early onset of CRSD, the ease of diagnosis, the high frequency of misdiagnosis and erroneous treatment, the potentially harmful psychological and adjustment consequences, and the availability of promising treatments, all indicate the importance of greater awareness of these disorders.
Archives of Internal Medicine.