Human body temperature

showing a temperature reading of Taking a human's temperature is an initial part of a full clinical examination. There are various types of medical thermometers, as well as sites used for measurement, including: • Under the armpit (axillary temperature) • In the mouth (oral temperature) • In the rectum (rectal temperature) • In the ear (tympanic temperature) • On the skin of the forehead over the temporal artery • Using heat flux sensors Variations , 1910) Temperature control (thermoregulation) is a homeostatic mechanism that keeps the organism at optimum operating temperature, as the temperature affects the rate of chemical reactions. In humans, the average internal temperature is widely accepted to be , a "normal" temperature established in the 1800s. But newer studies show that average internal temperature for men and women is . 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. The normal human body temperature is often stated as . With increased age, both average body temperature and the amount of daily variability in the body temperature tend to decrease. The study's authors believe the most likely explanation for the change is a reduction in inflammation at the population level due to decreased chronic infections and improved hygiene. Measurement methods Different methods used for measuring temperature produce different results. The temperature reading depends on which part of the body is being measured. The typical daytime temperatures among healthy adults are as follows: • Temperature in the rectum (rectal), vagina, or in the ear (tympanic) is about Each measurement method also has different normal ranges depending on sex. This includes tympanic infrared thermometers in children. Variations due to outside factors Sleep disturbances also affect temperatures. Normally, body temperature drops significantly at a person's normal bedtime and throughout the night. Short-term sleep deprivation produces a higher temperature at night than normal, but long-term sleep deprivation appears to reduce temperatures. Insomnia and poor sleep quality are associated with smaller and later drops in body temperature. Similarly, waking up unusually early, sleeping in, jet lag and changes to shift work schedules may affect body temperature. == Concept ==

Fever A temperature setpoint is the level at which the body attempts to maintain its temperature. When the setpoint is raised, the result is a fever. Most fevers are caused by infectious disease and can be lowered, if desired, with antipyretic medications. An early morning temperature higher than or a late afternoon temperature higher than is normally considered a fever, assuming that the temperature is elevated due to a change in the hypothalamus's setpoint. If temperature is raised, but the setpoint is not raised, then the result is hyperthermia. Hyperthermia Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate. It is usually caused by prolonged exposure to high temperatures. The heat-regulating mechanisms of the body eventually become overwhelmed and unable to deal effectively with the heat, causing the body temperature to climb uncontrollably. Hyperthermia at or above about is a life-threatening medical emergency that requires immediate treatment. Common symptoms include headache, confusion, and fatigue. If sweating has resulted in dehydration, then the affected person may have dry, red skin. In a medical setting, mild hyperthermia is commonly called heat exhaustion or heat prostration; severe hyperthermia is called heat stroke. Heatstroke may come on suddenly, but it usually follows the untreated milder stages. Treatment involves cooling and rehydrating the body; fever-reducing drugs are useless for this condition. This may be done by moving out of direct sunlight to a cooler and shaded environment, drinking water, removing clothing that might keep heat close to the body, or sitting in front of a fan. Bathing in tepid or cool water, or even just washing the face and other exposed areas of the skin, can be helpful. With fever, the body's core temperature rises to a higher temperature through the action of the part of the brain that controls the body temperature; with hyperthermia, the body temperature is raised without the influence of the heat control centers. Hypothermia In hypothermia, body temperature drops below that required for normal metabolism and bodily functions. In humans, this is usually due to excessive exposure to cold air or water, but it can be deliberately induced as a medical treatment. Symptoms usually appear when the body's core temperature drops by below normal temperature. Basal body temperature Basal body temperature is the lowest temperature attained by the body during rest (usually during sleep). It is generally measured immediately after awakening and before any physical activity has been undertaken, although the temperature measured at that time is somewhat higher than the true basal body temperature. In women, temperature differs at various points in the menstrual cycle, and this can be used in the long term to track ovulation both to aid conception or avoid pregnancy. This process is called fertility awareness. Core temperature Core temperature, also called core body temperature, is the operating temperature of an organism, specifically in deep structures of the body such as the liver, in comparison to temperatures of peripheral tissues. Core temperature is normally maintained within a narrow range so that essential enzymatic reactions can occur. Significant core temperature elevation (hyperthermia) or depression (hypothermia) over more than a brief period of time is fatal. Temperature examination in the heart, using a catheter, is the traditional gold standard measurement used to estimate core temperature (oral temperature is affected by hot or cold drinks, ambient temperature fluctuations as well as mouth-breathing). Since catheters are highly invasive, the generally accepted alternative for measuring core body temperature is through rectal measurements. Rectal temperature is expected to be approximately higher than an oral temperature taken on the same person at the same time. Ear thermometers measure temperature from the tympanic membrane using infrared sensors and also aim to measure core body temperature, since the blood supply of this membrane is directly shared with the brain. However, this method of measuring body temperature is not as accurate as rectal measurement and has a low sensitivity for fever, failing to determine three or four out of every ten fever measurements in children. Internal variation Measurement within the body finds internal variation temperatures as different as for the radial artery and for the brachial artery. It has been observed that "chaos" has been "introduced into physiology by the fictitious assumption of a constant blood temperature". == Temperature variation ==

Hot • or more – Almost certainly death will occur; however, people have been known to survive up to . • – Normally death, or there may be serious brain damage, convulsions, and shock. Cardio-respiratory collapse will likely occur. • – Subject may turn red. They may become comatose, be in severe delirium, and convulsions can occur. • – (Medical emergency) – Fainting, severe headache, dizziness, confusion, hallucinations, delirium, and drowsiness can occur. There may also be palpitations and breathlessness. • – Fainting, dehydration, weakness, headache, breathlessness, and dizziness may occur as well as profuse sweating. • – Severe sweating, and red. Fast heart rate and breathlessness. There may be exhaustion accompanying this. Children and people with epilepsy may suffer convulsions at this temperature. • – (Classed as hyperthermia if not caused by a fever) – Feeling hot, sweating, feeling thirsty, feeling very uncomfortable. • — Classed as a slight fever. May lose appetite, feeling hot, feeling uncomfortable, feeling thirsty. Normal • is a typically reported range for normal body temperature. The lowest recorded core temperature from a patient with accidental hypothermia who survived without neurological sequelae is . There are non-verbal corporal cues that can hint at an individual experiencing a low body temperature, which can be used for those with dysphasia or infants. Examples of non-verbal cues of coldness include stillness and being lethargic, unusual paleness of skin among light-skinned people, and, among males, shrinkage, and contraction of the scrotum. ==Effect of environment==

Environmental conditions, primarily temperature and humidity, affect the ability of the mammalian body to thermoregulate. The psychrometric temperature, of which the wet-bulb temperature is the main component, largely limits thermoregulation. It was thought that a wet-bulb temperature of about was the highest sustained value consistent with human life. A 2022 study on the effect of heat on young people found that the critical wet-bulb temperature at which heat stress can no longer be compensated, Twb,crit, in young, healthy adults performing tasks at modest metabolic rates mimicking basic activities of daily life was much lower than the usually assumed, at about in humid environments, but progressively decreased in hotter, dry ambient environments. At low temperatures the body thermoregulates by generating heat, but this becomes unsustainable at extremely low temperatures. == Historical understanding ==

In the 19th century, most books quoted "blood heat" as 98 °F, until a study published the mean (but not the variance) of a large sample as . Subsequently, that mean was widely quoted as "37 °C or 98.4 °F" until editors realized 37 °C is equal to 98.6 °F, not 98.4 °F. The 37 °C value was set by German physician Carl Reinhold August Wunderlich in his 1868 book, which put temperature charts into widespread clinical use. Dictionaries and other sources that quoted these averages did add the word "about" to show that there is some variance, but generally did not state how wide the variance is. == References ==