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.
