Our bodies are constantly experiencing changes from the external environment,
whether it’s changing seasons or the variety of food we eat. Despite these changes, our biological
systems are able to function normally because of something called homeostasis. Through homeostasis,
our bodies achieve optimal internal conditions to maintain biological stability, which is measured
in a certain numerical range around a set point. A simple way to think about a set point is how we
use a thermostat to maintain house temperature. Once you set the temperature the system monitors
when it gets too cold and turns the furnace on to heat the house. When the furnace heats the house
to the desired temperature, your set point, or above, the furnace shuts off to cool the house
back down. This is a constant back and forth process to ensure the desired temperature is
always maintained. But how does this process work in the body? Let’s take a closer look!
Our biological systems use processes known as feedback to help maintain ideal internal
conditions. There are two main types: positive feedback and negative feedback. Positive feedback
moves biological systems away from the set point, and negative feedback brings them back to it
Now, let’s look at positive and negative feedback in action within our bodies!
The birth of a child is primarily controlled by positive feedback.
The brain releases the oxytocin hormone at the start of labor,
which causes muscles in the uterus to contract in waves. These contractions trigger the brain
to produce even more oxytocin, which leads to even more contractions, helping to push the
baby out of the uterus. And this process continues until the baby is delivered.
What about negative feedback loops? Negative feedback keeps our bodily processes
near the set point. One example is blood sugar maintenance. When we eat, our blood sugar levels
rise, but prolonged high blood sugar levels can lead to serious health problems. A molecule called
insulin is released in response to increased blood sugar, which helps sugar molecules enter
cells to be used for energy and simultaneously lowers levels in the blood back to the set point.
But that’s not all! Some forms of negative feedback can actually anticipate
changes in a biological system because simply turning certain biological processes on or off
isn’t enough to effectively maintain the set point. So our bodies have come up
with a few additional clever tricks: for example a negative feed forward system.
Here, the body is able to anticipate when a change is about to take place, and make adjustments in
advance to avoid large imbalances. A biological example is maintenance of core body temperature.
Internal organs, like the heart and brain, are extremely sensitive to small temperature changes.
Our skin, however, is less sensitive to environmental changes , so any temperature
adjustments detected through our skin will signal to the brain to take preventative measures,
like redirecting blood flow to internal organs and shivering to help maintain
core body temperature. If our body only used on/off negative feedback, then our
core body temperature would reach dangerous levels before the body was able to fix it.
But sometimes, feedback loops don’t work properly and cause health problems.
Congestive heart failure, for example, occurs when a positive feedback loop
goes awry. Here, heart blockages lead to abnormal blood pressure, which the nervous
system detects and attempts to correct by sending signals to the heart to pump harder.
This leads to more heart damage, which further disrupts blood pressure and so on.
As you can see, homeostasis is essential to our overall health, but actually all systems, like
cars and computers use these similar mechanisms to function normally. So, the governing principles
of homeostasis ensures that not only we, but also the world around us is always in balance