How Is Body Temperature Controlled?
Labels Fever
The body adjusts its temperature in much the same way that the thermostat
in a house works. With a thermostat, people set the temperature
they want, and the heating or cooling system clicks on until the inside
of the house reaches the right temperature. After that, the heater or air
conditioner clicks on and off automatically to keep the temperature in the
house hovering around the desired temperature.
The body’s thermostat is located in the hypothalamus (hy-po-THALa-
mus), a small part of the brain that also helps to regulate hunger, thirst,
awareness of pleasure, and awareness of pain. The thermostat region of the
hypothalamus, called the thermoregulatory (ther-mo-REG-u-la-tor-ee)
center, normally keeps the body’s temperature hovering at around 98.6
degrees Fahrenheit (F) (36.8 degrees Centigrade [C]).
Like a house, the body has sensors that tell the thermostat if the temperature
inside is rising or falling. In the body, these sensors are cells
located in the skin and in the brain itself. If the sensors report that the
body’s temperature is rising, the body’s cooling system clicks on, telling
the cells to burn less fuel and produce less heat. The blood vessels expand
to let heat escape from the skin (the evaporating sweat draws heat away
from blood vessels), sweat pours out to cool the body as it evaporates,
and the brain may get a bright idea: “Let’s go into the shade and have a
cold drink.”
Fever
With fever, the thermostat in the brain is reset to a higher temperature.
Instead of keeping the body’s temperature hovering at around
98.6 degrees F, the body’s heating and cooling systems may keep the temperature
at 100 to 102 degrees F or even higher.
Normal temperature varies a bit from person to person and from
morning to evening, making it hard to state precisely where normal ends
and fever begins. In fact, temperature measured at different places in the
body can also be different. Temperature measured at the mouth can be
one whole degree Fahrenheit lower than the actual core body temperature.
For this reason, core body temperature is best measured at the rectum
or at the ear. Most doctors say that a core body temperature at or above
100.4 degrees F (38 degrees C) should be considered a fever. Core body
temperature above 104 degrees F (40 degrees C) is generally considered a
high fever.
Hyperthermia
Sometimes a person’s temperature can rise for a different
reason. Hyperthermia (hy-per-THER-me-a), quite different from fever,
occurs when the heat outside is too much for the body’s cooling system to
handle, making body temperature (and the set point) rise. The most severe
cases of hyperthermia tend to occur in people who cannot sweat as much
as others, such as elderly people or those taking certain medications.
in a house works. With a thermostat, people set the temperature
they want, and the heating or cooling system clicks on until the inside
of the house reaches the right temperature. After that, the heater or air
conditioner clicks on and off automatically to keep the temperature in the
house hovering around the desired temperature.
The body’s thermostat is located in the hypothalamus (hy-po-THALa-
mus), a small part of the brain that also helps to regulate hunger, thirst,
awareness of pleasure, and awareness of pain. The thermostat region of the
hypothalamus, called the thermoregulatory (ther-mo-REG-u-la-tor-ee)
center, normally keeps the body’s temperature hovering at around 98.6
degrees Fahrenheit (F) (36.8 degrees Centigrade [C]).
Like a house, the body has sensors that tell the thermostat if the temperature
inside is rising or falling. In the body, these sensors are cells
located in the skin and in the brain itself. If the sensors report that the
body’s temperature is rising, the body’s cooling system clicks on, telling
the cells to burn less fuel and produce less heat. The blood vessels expand
to let heat escape from the skin (the evaporating sweat draws heat away
from blood vessels), sweat pours out to cool the body as it evaporates,
and the brain may get a bright idea: “Let’s go into the shade and have a
cold drink.”
Fever
With fever, the thermostat in the brain is reset to a higher temperature.
Instead of keeping the body’s temperature hovering at around
98.6 degrees F, the body’s heating and cooling systems may keep the temperature
at 100 to 102 degrees F or even higher.
Normal temperature varies a bit from person to person and from
morning to evening, making it hard to state precisely where normal ends
and fever begins. In fact, temperature measured at different places in the
body can also be different. Temperature measured at the mouth can be
one whole degree Fahrenheit lower than the actual core body temperature.
For this reason, core body temperature is best measured at the rectum
or at the ear. Most doctors say that a core body temperature at or above
100.4 degrees F (38 degrees C) should be considered a fever. Core body
temperature above 104 degrees F (40 degrees C) is generally considered a
high fever.
Hyperthermia
Sometimes a person’s temperature can rise for a different
reason. Hyperthermia (hy-per-THER-me-a), quite different from fever,
occurs when the heat outside is too much for the body’s cooling system to
handle, making body temperature (and the set point) rise. The most severe
cases of hyperthermia tend to occur in people who cannot sweat as much
as others, such as elderly people or those taking certain medications.
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