| |
| Body Temperature |
| |
| When someone is unwell, the first thing a doctor
or a patient checks up is the body temperature to find out whether the person
has fever. Raised body temperature makes a person realize that he or she
is unwell. |
| |
| What is the normal body temperature? |
Body temperature in a healthy, young person
usually falls within 97.5 F (36.2 C) to 98.9 F (37.2 C). But it can vary
during the day by as much as 1 or 2 degrees. It tends to be lowest in the
morning, from 2 a.m. to 4 a.m., when the body is resting. It tends to be
warmest in the late afternoon, from 4 p.m. to 6 p.m., after the body has
been active for a while. This diurnal variation is present usually even
in those who work night shifts, probably because the body’s internal mechanisms
are very resistant to change.
But a person's metabolic rate, which is determined by the genetic makeup,
lifestyle, environment and many other factors, can cause the normal body
temperature to fall outside the limits mentioned above. |
| |
| How is the body temperature regulated? |
The body temperature adjusts itself to stay within a set
range, regardless of external temperature changes. The hypothalamus in the
brain controls the body temperature.
For example, if the body heats up from exertion or physical activity, the
hypothalamus triggers the body to sweat and release the heat. |
| |
| What is hyperthermia and hypothermia? |
Hyperthermia is the condition when excess heat
production over rides the normal mechanism of the body to maintain normal
body temperature.
Hypothermia is an extreme lowering of body temperature, usually to less
than 95 F (35 C).
Hypothermia is usually caused by prolonged exposure to severe cold, especially
when the body is wet, but it may occur at temperatures only slightly below
normal, after trauma and in the elderly, or in those who are very inactive
or inadequately nourished. |
| |
| Why does a person have fever? |
| An infection is usually the
most common cause of fever. When there is
an infection or inflammation, chemicals called cytokines are released into the bloodstream.
These make the hypothalamus alter the thermostat for temperature regulation. Temperature
may also rise during noninfectious illnesses such as strokes,
blood clots in the arteries or veins and gout attacks. |
| |
| When can we say a person has fever? |
| It is difficult to pinpoint to a temperature
level to say that any reading above that indicates that a person is having
fever. The body temperature depends on age, time of the day, medical conditions,
etc. A cutoff of 100 F (37.8 C) is often used, but lesser temperature elevations
could also indicate serious infections, especially in people who normally
have a colder body temperature. |
| |
| Can the body temperature be higher even when a person does
not have fever? |
| There are many physiological factors that can change the
body temperature. |
Physical activity: After strenuous exercise, the hypothalamus
takes a longer time to bring the body temperature to the normal level.
For example, after a long running race, the athlete may have a body
temperature of 102 F (38.9 C).
Ovulation: During the two weeks before ovulation, the part of
the menstrual cycle when an egg is released from the ovary, a woman
may have a body temperature lower than normal. It then increases by
about 1 degree, with ovulation. This is because progesterone, one of
the hormones that regulate the menstrual cycle, is released at this
time. This hormone causes an increase in body temperature, which is
an indicator to show that ovulation may have occurred.
Pregnancy: Body temperature in women is increased during the
first three months of pregnancy. This may be due to increased blood
flow in a pregnant woman.
Newborns: In infants, the regulation of body temperature is not
as developed as in adults. Their body temperature may rise when they
are exposed to heat or when too many warm clothes are used. The body
temperature may also come down very much, if the infant is exposed to
cold. Babies also have a body surface area that is large in comparison
with the body weight. Since heat loss occurs through the skin, a relatively
large surface area increases the loss of heat.
Elders: Body temperature tends to decline with age. People older
than 65 may have an average body temperature that is 1 to 2 degrees
lower than those who are younger than 40. This may be due to a less-active
metabolism, or because elders are less active. The sweat glands are
also less active in the elderly and require higher body temperatures
to trigger the sweating mechanism. This makes the elderly more prone
to heat exhaustion.
Smoking: This could reduce the oxygen in the blood and constrict
the blood vessels. Such changes could lower body temperature, especially
in the extremities.
|
| |
| In which part of the body can temperature be measured for
accurate readings? |
The most convenient part of the body to take a
temperature reading is the mouth. But consumption of hot or cold drinks, improper
thermometer placement and even breathing changes can give a false reading.
Temperatures measured under the armpit (axilla) are even less accurate.
The core body temperature is best measured in the rectum. Rectal temperature
is usually about 1 degree higher than oral temperatures. Axillary temperature
is about 1 degree lower than oral temperature. |
| |
FAQs