What is homeostasis? To be brief and to the
point, homeostasis is the relatively constant state
maintained by the body. Mainly this means that
over time, the internal body will maintain a
stable environment. So, for example, if the external
temperature is cold or hot, the internal body temperature
will remain relatively constant at 98.6 degrees
fahrenheit or 37 degrees celsius, the internal body temp may vary a
little above or below this number but that will still be considered normal. So, let’s say we took someone’s body
temperature over a certain time period. If we plot that on a chart it may look
something like this (graphic on screen). Here, body temperature rose slightly,
and here it fell a little. But, the normal body temperature
range is from 97.7 to 99.5 degrees. So, our subject was inside the normal
range throughout that time span. Homeostasis doesn’t just
apply to body temperature, but many other conditions as well. The human body needs to maintain a certain
range of nutrients in the blood stream, such as water, glucose, sodium,
and other elements as well. We get our blood work done
from time to time to check and make sure we don’t have high
glucose or cholesterol levels, or too low levels of certain
vitamins or minerals. This in essence is to
check and make sure our body is maintaining
homeostatic conditions. Set point is an important term
when discussing homeostasis. Set point is a normal range
that the body tries to stay in. For instance, the normal range for systolic
blood pressure is between 80 and 120. So homeostasis is sought
by the body to keep systolic blood pressure in
this range or set point. However, the body can change the set point. In many people weight gain leads
to higher systolic blood pressure. This could be due to many factors,
but the point is that the body changed the blood pressure
set point to keep homeostasis. So now, maybe after the weight gain, someone’s systolic blood
pressure may be at 140, which is considered unhealthy
and at a risk for some diseases, but the body felt to keep homeostasis it
needed to change and pump blood harder. The ability of the body to maintain
homeostasis is crucial to life, and each of the systems in the
body plays important roles. It is often times easier
to understand homeostasis by constructing a model to
make the concept clearer. Many sources use a fish tank comparison. Here we have a fish tank
filled with water. The water represents body fluid, or
the internal environment. The glass that encloses the water
or fluid would be the skin creating a barrier separating
internal from external. The fish in the tank represent cells,
which obviously want to stay alive. But the cells need nutrients from the
external environment in order to survive. The cells need oxygen, so we can
put an air pump in the tank, which would represent the lungs,
pumping oxygen into the tank. Ok, now we need a filter to get rid of
wastes, which would represent the kidneys. Next we need to add a heater to
keep a constant temperature, and the heater would represent the muscles. And finally we need food, or at least
the nutrients contained in food, so, we hook up a feeder to our fish
tank to feed those fish, or cells, and the feeder would represent
the digestive system. So, our fish tank is complete,
and with everything working together, we have relatively
stable and constant conditions, which equals homeostasis. Keep in mind that our fish
tank model only covers a few of the aspects involved in
maintaining homeostasis, as there are actually far more mechanisms involved in the body keeping
at a state of homeostasis. And that, be the basics on homeostasis.
