A Statistical Analysis of Human Body Temperature. By: Dhanalakshmi Pantangi Praneetha Mukhatira Yaping Sun. Introduction: Normal Body temperature
Human Body Temperature
Normal Body temperature
The normal core body temperature of a healthy, resting adult human being is stated to be at 98.6 degrees Fahrenheit or 37.0 degrees Celsius..
However, body temperature varies from person to person and is affected by factors such as
exercise, sleep, eating and drinking, and time of day.
The body's surface temperature rises and falls in response to the environment
Body temperature is maintained by the hypothalamus,
which constantly monitors blood temperature and activates mechanisms to compensate for changes.
When the body's surface temperature falls, the hypothalamus sends nerve impulses to the skin to stimulate shivering, which generates heat by muscle activity, and to restrict the blood vessels in the skin, which limits heat loss.
When the surface temperature rises, the hypothalamus stimulates the sweat glands in the skin to produce sweat and dilates the blood vessels in the skin to increase heat loss
. Because of the complexity of the human thermoregulatory system, there are an infinite number of components that may be included, or omitted depending on the primary use of the thermoregulatory model.
Temperature refers to the degree of hotness or coldness of a body or environment.
Temperature may be defined as the condition of a body which determines the transfer of heat to or from other bodies.
Particularly, it is a manifestation of the average translational kinetic energy of the molecules of a substance due to heat agitation.
High temperature means that an object's constituent parts are moving around energetically. Absolute zero (0°K) is the point at which atomic and molecular motion stops; this temperature has not yet been achieved on earth.
We take measurement units for granted as long as we don't have to convert to some other system. But converting units is always trouble.
NASA apparently lost the Mars Climate Orbiter spacecraft because of a problem converting units.
The familiar but over-exact 98.6 °F body temperature is also a units problem caused by preserving too many digits after converting. ." Different systems of units are so human, and so subject to human error. All modern temperature scales are based on measuring two points on a scale and extrapolating the rest..
The German physician Carl Reinhold August Wunderlich (1815 - 1877) made the original study of normal body temperature in the 1800s by doing a statistical study of thousands of people in Europe.
He was one of the first to describe fever as a symptom, not a disease by itself. He averaged his results to 37° Celsius, rounded to the nearest degree. But +/- 0.5 °C, is nearly a full degree Fahrenheit after converting by the formula °F = (9/5) °C + 32
Medical Service, Veterans Affairs Medical Center, Baltimore.
To evaluate critically Carl Wunderlich's axioms on clinical thermometry A critical appraisal of 98.6 degrees F, the upper limit of the normal body temperature, and other legacies of Carl Reinhold August Wunderlich.
Oral temperatures were measured one to four times daily for 3 consecutive days using an electronic digital thermometer .Taken from hundred forty-eight healthy men and women aged 18 through 40 years.
RESULTS--Our findings conflicted with Wunderlich's in that 36.8 degrees C (98.2 degrees F) rather than 37.0 degrees C (98.6 degrees F) was the mean oral temperature of our subjects; 37.7 degrees C (99.9 degrees F) rather than 38.0 degrees C (100.4 degrees F) was the upper limit of the normal temperature range; maximum temperatures, like mean temperatures, varied with time of day; and men and women exhibited comparable thermal variability.); women had slightly higher normal temperatures than men; and there was a trend toward higher temperatures among black than among white subjects.
CONCLUSIONS--Thirty-seven degrees centigrade (98.6 degrees F) should be abandoned as a concept relevant to clinical thermometry; 37.2 degrees C (98.9 degrees F) in the early morning and 37.7 degrees C (99.9 degrees F) overall should be regarded as the upper limit of the normal oral temperature range in healthy adults aged 40 years or younger.
The external heat transfer mechanisms are radiation, conduction and convection and evaporation of perspiration
The process is far more than the passive operation of these heat transfer mechanisms,
however. The body takes a very active role in temperature regulation.
The temperature of the body is regulated by neural feedback mechanisms which operate primarily through the hypothalamus.
The hypothalamus contains not only the control mechanisms, but also the key temperature sensors. Under control of these mechanisms, sweating begins almost precisely at a skin temperature of 36.8°C and increases rapidly as the skin temperature rises above this value.
Temperature Regulation of the Human Body
An equation for the body heat balance can be written as M ± W = ± R ± C ± E ± S [W/m²] where M is the rate at which thermal energy is produced by the body through metabolic processes, W is the rate of work produced by or on the body, R is the rate of radiant heat exchange with the surroundings, C is the rate of convective heat exchange with the surroundings, E is the rate of heat loss due to evaporation of body water, and S is the rate of heat storage in the body. Numerous studies have confirmed that in many species, an absorbed dose of microwave energy equivalent to the resting metabolic heat production elevates the deep body temperature of the animal by 1 degree or more. S should ideally be close to zero in order to prevent body temperature changes
We earlier defined the thermoregulatory model.
We modeled a person exercising on a level treadmill. We will assume that the resultant heat loss (wastage) is a parabolic function of speed, with a value of 11.2 Cal / min at a speed of 9 kmph.
We will further assume that y skin temperature varies parabolically from 28.2 C at an ambient temperature of 9.5 C to 37.2 C at an ambient temperature of 35 C.
Finally, we assume that you do not sweat when the ambient temperature is below 30 C and that above 30 C the rate of sweat is proportional to the amount by which your skin temperature exceeds 30 C.
These assumptions are based on studies on medical students. We will supplement them with an estimate of the amount of water vapor exhausted during respiration which is proportional to the rate of exercise.
Since the net heat loss or gain is a function of three variables (ambient temperature, rate of walking and wind speed), we have to analyze a three dimensional field.
This example shows the waste heat in red, evaporative losses in blue, convective losses in green and conductive and radiative losses in black, all as a function of ambient temperature for a given exercise level (6 km/hr) and wind velocity (5 m/s).
1.Pre-exercise temperature levels were similar in the afternoon (1330-1430: 37.06 ± 0.06°C) and at night (2230-2330: 37.13 ±0.09°C) but were significantly lower in the early morning (0400-0500:36.37 ± 0.07°C),
consistent with the well-known diurnal variationin resting core body temperature.
Exercise-induced elevationsof temperature were higher in the early morning (1.31 ± 0.08°C)than in the afternoon (0.96 ± 0.09°C, P < 0.05) or at night (0.89± 0.10°C, P < 0.05),
probably because the exercise-induced elevationwas superimposed on the normal early morning increase. The areasunder the curve for body temperature during exercise were similarat each time of day.