body temperature

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Related to body temperature: basal body temperature, Low body temperature


the degree of sensible heat or cold, expressed in terms of a specific scale. See Table of Temperature Equivalents in the Appendices. Body temperature is measured by a clinical thermometer and represents a balance between the heat produced by the body and the heat it loses. Though heat production and heat loss vary with circumstances, the body regulates them, keeping a remarkably constant temperature. An abnormal rise in body temperature is called fever.

Normal Body Temperature. Body temperature is usually measured by a thermometer placed in the mouth, the rectum, or the auditory canal (for tympanic membrane temperature). The normal oral temperature is 37° Celsius (98.6° Fahrenheit); rectally, it is 37.3° Celsius (99.2° Fahrenheit). The tympanic membrane temperature is a direct reflection of the body's core temperature. These values are based on a statistical average. Normal temperature varies somewhat from person to person and at different times in each person. It is usually slightly higher in the evening than in the morning and is also somewhat higher during and immediately after eating, exercise, or emotional excitement. Temperature in infants and young children tends to vary somewhat more than in adults.
Temperature Regulation. To maintain a constant temperature, the body must be able to respond to changes in the temperature of its surroundings. When the outside temperature drops, nerve endings near the skin surface sense the change and communicate it to the hypothalamus. Certain cells of the hypothalamus then signal for an increase in the body's heat production. This heat is conducted to the blood and distributed throughout the body. At the same time, the body acts to conserve its heat. The arterioles constrict so that less blood will flow near the body's surface. The skin becomes pale and cold. Sometimes it takes on a bluish color, the result of a color change in the blood, which occurs when the blood, flowing slowly, gives off more of its oxygen than usual. Another signal from the brain stimulates muscular activity, which releases heat. Shivering is a form of this activity—a muscular reflex that produces heat.

When the outside temperature goes up, the body's cooling system is ordered into action. Sweat is released from sweat glands beneath the skin, and as it evaporates, the skin is cooled. Heat is also eliminated by the evaporation of moisture in the lungs. This process is accelerated by panting.

An important regulator of body heat is the peripheral capillary system. The vessels of this system form a network just under the skin. When these vessels dilate, they allow more warm blood from the interior of the body to flow through them, where it is cooled by the surrounding air.
Abnormal Body Temperature. Abnormal temperatures occur when the body's temperature-regulating system is upset by disease or other physical disturbances. fever usually accompanies infection and other disease processes. In most cases when the oral temperature is 37.8°C (100°F) or over, fever is present. Temperatures of 40°C (104°F) or over are common in serious illnesses, although occasionally very high fever accompanies an illness that causes little concern. Temperatures as high as 41.7°C (107°F) or higher sometimes accompany diseases in critical stages. Subnormal temperatures, below 35.6°C (96°F) occur in cases of collapse; see also symptomatic hypothermia.
absolute temperature (T) that reckoned from absolute zero (−273.15°C), expressed on an absolute scale.
basal body temperature (BBT) the temperature of the body under conditions of absolute rest; it has a slight sustained rise during the luteal phase of the menstrual cycle and can be used as an indirect indicator of when ovulation has occurred.
body temperature the temperature of the body of a human or animal; see temperature.
core temperature the temperature of structures deep within the body, as opposed to peripheral temperature such as that of the skin.
critical temperature that below which a gas may be converted to a liquid by increased pressure.
normal temperature the body temperature usually registered by a healthy person, averaging 37°C (98.6°F).
risk for imbalanced body temperature a nursing diagnosis accepted by the North American Nursing Diagnosis Association, defined as a state in which an individual is at risk of failure to maintain body temperature within the normal range.
subnormal temperature temperature below the normal. See also symptomatic hypothermia.

body temperature

the level of heat produced and sustained by the body processes. Variations and changes in body temperature are major indicators of disease and other abnormalities. Heat is generated within the body through metabolism of nutrients and lost from the body surface through radiation, convection, and evaporation of perspiration. Heat production and loss are regulated and controlled in the hypothalamus and brainstem. Fever is usually a function of an increase in heat generation; however, some abnormal conditions, such as congestive heart failure, produce slight elevations of body temperature through impairment of the heat loss function. Contributing to the failure to dissipate heat are reduced activity of the heart, lower rate of blood flow to the skin, and the insulating effect of edema. Diseases of the hypothalamus or interference with the other regulatory centers may produce abnormally low body temperatures. Normal adult body temperature, as measured orally, is 98.6° F (37° C). Oral temperatures ranging from 96.5° F to 99° F are consistent with good health, depending on the person's physical activity, the environmental temperature, and that person's usual body temperature. Axillary temperature is usually from 0.5° F to 1° F lower than the oral temperature. Rectal temperatures may be 0.5° F to 1° F higher than oral readings. Body temperature appears to vary 1° F to 2° F throughout the day, with lows recorded early in the morning and peaks between 6 pm and 10 pm. This diurnal variation may increase in range during a fever. Whereas adult body temperature, normal and abnormal, tends to vary within a relatively narrow range, children's temperatures respond more dramatically and rapidly to disease, changes in environmental temperature, and levels of physical activity.
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Normal and abnormal body temperatures

body temperature

The temperature of the human body, which is warmer at the core (centrally)—usually between 36–37.5ºC—than at the periphery (extremities).

body temperature

is normally regulated so as to maintain a core temperature, that of the blood and the internal organs, of 37°C ± 0.5-1°C. Determined by the balance between metabolic heat production (varying with muscular activity) and heat loss (from the skin surface, in expired air and with the excreta). Heat loss is influenced by external factors (ambient temperature, humidity, air movement and clothing) and regulated physiologically by the hypothalamus, via the autonomic nervous system, in response to changes in blood temperature and afferent information from skin receptors. Constriction or dilatation of skin blood vessels varies the skin temperature and hence the heat loss, effectively changing the thickness of the insulating 'shell' around the 'core'. Sweating is stimulated for additional evaporative heat loss and shivering for additional metabolic heat production. See also heat illness, hypothermia.


the degree of sensible heat or cold, expressed in terms of a specific scale. See also hypothermia, hyperthermia.

absolute temperature
that reckoned from absolute zero (−459.67°F or −273.15°C).
air temperature
the temperature of the surrounding air as measured by a dry-bulb thermometer.
ambient temperature
temperature of the immediate environment.
body temperature
a prime technique for assessing health status of a patient. Always a rectal temperature. Average temperatures above which hyperthermia, pyrexia or fever can be said to occur are listed under pyrexia.
critical temperature
1. that below which a gas may be converted to a liquid by pressure.
2. the environmental temperature at which the body is unable to maintain a constant body temperature and at which heat production must be increased (cold temperatures) or at which heat loss must be increased (high temperatures).
effective temperature
the combination of air temperature, humidity and wind speed. See also temperateness index.
environmental temperature
air temperature.
nonpermissive temperature
one at which a conditional gene mutation is nonfunctional. See also temperature-sensitive mutation.
normal body temperature
that usually registered by a healthy animal. See pyrexia.
permissive temperature
one at which a conditional gene mutation can express its normal function. See also temperature-sensitive mutation.
premortal temperature fall
the sudden fall in body temperature of a previously fevered animal just before death.
rectal temperature
the body temperature as measured by a rectal thermometer which has been in situ and in contact with the mucosa of the rectum with the anal sphincter tightly closed for at least 30 seconds. Alternative equipment is a dipolar electrode in a rectal probe.
temperature stress
exposure to excessively high or low environmental temperature.
windchill temperature
a combination of wind velocity and air temperature. See also effective temperature (above).

Patient discussion about body temperature

Q. what is the red line when your body temperature drops before you are getting hypothermia?

A. Hypothermia is a condition in which an organism's temperature drops below that required for normal metabolism and function. For people in stage 1 hypethermia, body temperature drops by 1-2°C below normal temperature (35-36°C). Mild to strong shivering occurs. In stage 2, body temperature drops by 2-4°C (35-33 degrees). Shivering becomes more violent. Muscle mis-coordination becomes apparent and movements are slow and labored and there is mild confusuin. In stage 3, body temperature drops below approximately 32 °C (89.6 °F). Shivering usually stops and there's difficulty speaking, sluggish thinking, and amnesia start to appear. Cellular metabolic processes shut down. This is life threatening.

More discussions about body temperature
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