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Normal human body temperature, also known as normothermia or euthermia, is a concept that depends upon the place in the body at which the measurement is made, and the time of day and level of activity of the person. There is no single number that represents a normal or healthy temperature for all people under all circumstances using any place of measurement. Different parts of the body have different temperatures. Rectal and vaginal measurements, or measurements taken directly inside the body cavity, are typically slightly higher than oral measurements, and oral measurements are somewhat higher than skin temperature. The commonly accepted average core body temperature (taken internally) is 37.0 °C (98.6 °F). The typical oral (under the tongue) measurement is slightly cooler, at 36.8±0.7 °C, or 98.2±1.3 °F. In Russia and former Soviet countries, the commonly quoted value is 36.6 °C (97.9 °F), based on an armpit (axillary) reading. Although some people think of these numbers as representing the normal temperature, a wide range of temperatures has been found in healthy people.[3] In samples of normal adult men and women, the observed range for oral temperature is 33.2–38.2 °C (92–101 °F), for rectal it is 34.4–37.8 °C (94–100 °F), for the tympanic cavity it is 35.4–37.8 °C (96–100 °F) and for axillary it is 35.5–37.0 °C (96–99 °F). The time of day and other circumstances also affects the body's temperature. The core body temperature of an individual tends to have the lowest value in the second half of the sleep cycle (~04:30); the lowest point, called the nadir, is one of the primary markers for the human circadian rhythm ( biological clock). The body temperature also changes when a person is hungry, sleepy, or cold. In the early 18th century, Gabriel Fahrenheit originally used human body temperature as a reference point for his temperature scale, defining it to be 100°F. Later redefinition of his scale to use the boiling point of water as a reference point caused the numerical value for normal body temperature to drift. In 1861, Carl Reinhold August Wunderlich released his summary of the armpit, or axillary, temperatures of twenty five thousand people, and reported the mean to be 37.0 °C (98.6 °F), with a range of 36.25 °C (97.25 °F) to 37.5 °C (99.5 °F). He also identified the natural variations in temperature throughout the day and the variations between individuals, as well as differences based on sex and age, which were largely ignored in favor of an oversimplified single number. Wunderlich's thermometers were not calibrated to a standard setting—in 1861, no standard had been agreed upon—and he never explained his methods for compiling and describing the data he had collected, which would have been a monumental task before the availability of basic calculating machines. The one surviving, hand-made thermometer reads significantly higher than modern thermometers.

Variations Diurnal variation in body temperature, ranging from about 37.5 °C from 10 a.m. to 6 p.m., and falling to about 36.4 °C from 2 a.m. to 6 a.m. Temperature control (thermoregulation) is part of a homeostatic mechanism that keeps the organism at optimum operating temperature, as it affects the rate of chemical reactions. In humans the average oral temperature is 36.8 °C (98.2 °F), though it varies among individuals. However, no person always has exactly the same temperature at every moment of the day. Temperatures cycle regularly up and down through the day, as controlled by the person's circadian rhythm. The lowest temperature occurs about two hours before the person normally wakes up. Additionally, temperatures change according to activities and external factors.[7] Normal body temperature may differ as much as 0.5 °C (1.0 °F) from day to day.

Natural rhythms Body temperature normally fluctuates over the day, with the lowest levels around 4 a.m. and the highest in the late afternoon, between 4:00 and 6:00 p.m. (assuming the person sleeps at night and stays awake during the day). Therefore, an oral temperature of 37.2 °C (99.0 °F) would, strictly speaking, be normal in the afternoon but not in the morning. An individual's body temperature typically changes by about 0.5 °C (0.9 °F) between its highest and lowest points each day. Body temperature is sensitive to many hormones, so women have a temperature rhythm that varies with the menstrual cycle, called a circamensal rhythm. A woman's Basal Body Temperature (BBT) rises sharply after ovulation, as estrogen production decreases and progesterone increases. Fertility awareness programs use this predictable change to identify when a woman is able to become pregnant. During the luteal phase of the menstrual cycle, both the lowest and the average temperatures are slightly higher than during other parts of the cycle. However, the amount that the temperature rises during each day is slightly lower than typical, so the highest temperature of the day is not very much higher than usual.[6] Hormonal contraceptives both suppress the circamensal rhythm and raise the typical body temperature by about 0.6 °C (1.1 °F). Temperature also varies with the change of seasons during each year. This pattern is called a circannual rhythm. Studies of seasonal variations have produced inconsistent results. People living in different climates may have different seasonal patterns. Increased physical fitness increases the amount of daily variation in temperature. With increased age, both average body temperature and the amount of daily variability in the body temperature tend to decrease.[6] Elderly patients may have a decreased ability to generate body heat during a fever, so even a somewhat elevated temperature can indicate a serious underlying cause in geriatrics.

Frauen träumen wilder Aber woran liegt’s? Offenbar an den Hormonen. „Die Forschung hat gezeigt, dass der weibliche Hormonzyklus Träume beeinflussen kann“, zitiert die „Daily Mail“ Davina Mackai, Autorin des Buches „The Dream Whisperer“. „Vor der Periode tendieren wir dazu, mehr emotionale oder beklemmende Träume zu haben.“ Während Frauen im Schlaf ganze Abenteuer erleben, gestalten sich die Träume der Männer wesentlich unspektakulärer. „Frauen neigen zu einer größeren Vielfalt an Träumen als Männer“, erklärte die Traumforscherin Professor Kelly Bulkeley gegenüber der britischen Tageszeitung „Daily Mail“. „Frauen haben mehr Alpträume, mehr emotionale Träume, mehr surreale – und größere Schwierigkeiten mit dem Einschlafen.“ Die Erklärung dafür liefert eine Studie der Universität von Westengland. Die hat ergeben, dass Veränderungen bezüglich der weiblichen Körpertemperatur – hervorgerufen durch den Monatszyklus – der Grund für besonders intensive Träume sind. Nach dem Eisprung steigt die Temperatur an. Kurz vor der Periode fällt sie dann wieder. In dieser Zeit seien die Träume von Frauen oft aggressiver. Und: Sie bleiben eher in Erinnerung, so Studienleiterin Dr. Jennie Parker gegenüber der „Daily Mail“. Es überrascht wenig, dass auch ein heranwachsendes Baby im Mutterleib zu ungewöhnlich lebhaften Träumen führt. „Während der Schwangerschaft steigt der Hormonspiegel“, erklärte Victoria Dawson, Schlafexpertin und Mitverfasserin des Buches „Insomnia: The Essential Guide“ gegenüber „Daily Mail“. Die REM-Schlafphasen – diejenigen, in denen wir am meisten träumen – seien bei werdenden Müttern ebenfalls besonders häufig. „In den späten Phasen einer Schwangerschaft wird der Schlaf von Frauen außerdem oft gestört. Weil sie während des REM-Zyklus‘ aufwachen, ist es wahrscheinlicher, dass sie sich an die Träume erinnern.“ Außerdem nähmen die Alpträume zu. Von letzteren sind jedoch nicht nur Schwangere betroffen, sondern das weibliche Geschlecht im Allgemeinen: „Nur 19 Prozent der Männer berichteten von Alpträumen, verglichen mit 30 Prozent der Frauen“, so Dr. Parker. Dass Frauen sich meist besser an ihre Träume erinnern können, hängt offenbar auch damit zusammen, dass sie ihnen mehr Bedeutung beimessen. Wissenschaftliche Untersuchungen haben laut „Daily Mail“ ergeben, dass durch die Konzentration auf wichtige Gedanken eine Hirnregion angeregt wird, die mit dem Erinnerungsvermögen zusammenhängt. Oft werden Alpträume auch mit dem Konsum von Käse, Zigaretten oder Alkohol vor dem Schlafengehen in Verbindung gebracht. Dies führe nicht automatisch zu Horrorszenarien beim Schlummern, so Mackail.

Allerdings könnte der Verdauungsprozess den Schlaf oder das Schlafmuster beeinträchtigen. Sie empfiehlt daher, ein bis zwei Stunden vor dem Schlafengehen nichts mehr zu essen und sich zu entspannen. „Vermeiden sie stimulierende Getränke wie Cola, Kaffee und Tee nach 18 Uhr. Schauen Sie eine Stunde vor dem Zubettgehen kein Fernsehen oder checken Sie keine Mails mehr – versuchen Sie, klassische Musik oder eine Entspannungs-CD zu hören.“ 

Solche Methoden können für einen ruhigeren Schlaf sorgen. Manche Experte empfehlen auch, ein Schlaftagebuch zu führen. Dadurch können für die Nachtruhe schädliche Verhaltensmuster aufgedeckt werden.

Celsius In 1742 Swedish astronomer Anders Celsius (1701–1744) originally created a "reversed" version of the modern Celsius temperature scale wherein zero represented the boiling point of water and one hundred represented the freezing point of water. In his paper Observations of two persistent degrees on a thermometer, he recounted his experiments showing that the melting point of ice is essentially unaffected by pressure. He also determined with remarkable precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the zero point of his temperature scale, being the boiling point, would be calibrated at the mean barometric pressure at mean sea level. This pressure is known as one standard atmosphere. The BIPM's 10th General Conference on Weights and Measures (CGPM) later defined one standard atmosphere to equal precisely 1013250dynes per square centimeter (101.325kPa). In 1744, coincident with the death of Anders Celsius, the Swedish botanist Carolus Linnaeus (1707–1778) reversed Celsius's scale upon receipt of his first thermometer featuring a scale where zero represented the melting point of ice and 100 represented the boiling point. His custom-made "linnaeus-thermometer", for use in his greenhouses, was made by Daniel Ekström, Sweden's leading maker of scientific instruments at the time and whose workshop was located in the basement of the Stockholm observatory. As often happened in this age before modern communications, numerous physicists, scientists, and instrument makers are credited with having independently developed this same scale; among them were Pehr Elvius, the secretary of the Royal Swedish Academy of Sciences (which had an instrument workshop) and with whom Linnaeus had been corresponding; Christian of Lyons; Daniel Ekström, the instrument maker; and Mårten Strömer (1707–1770) who had studied astronomy under Anders Celsius.

2014: 9th October: 21,343 views