Homeostasis Within the Human Body
What is Homeostasis
Homeostasis is the ability of anything (doesn't necessarily have to be in the human body) to be able to maintain a relatively constant stable environment in order to survive. In other words, there are normal standards in which something must stay within to live.
Here's an example. The average human temperature is 98.6 degrees Fahrenheit. If the temperature was to go to 120 degrees, the human would die. If the temperature was to go down to 85 degrees, they would die. The temperature must be within certain guidelines or else the person will die.
Temperature can vary- however. If you have a temperature of 95.2, you can live. 98.6 is the normal, ideal value, or a set point. Body temperature can rise and fall, and our body can adjust to this, and get ourselves to a point within a normal range. This is done doing a negative feedback system.
A negative system feedback means that there is a deviation from the set point. Let's say your temperature will go up to 101.2. This is a deviation from the normal range. Your body will respond to this by sweating, which cools you down, and you'll return to your normal range. Or, another example, you have the flu. This is causing your temperature to raise (because your body is trying to heat up the virus and kill it), while your body is raising it's temperature, you will sweat, making sure that you do not overheat and die. Once the virus is gone, your body will take care of itself.
Most negative feedback systems have three components: A receptor, a control center, and an effector.
Receptors will monitor your body for some sort of value. This is what tells your body to know "98.6 is a normal value for a temperature." The Control Center will define the set points. This says "Ok, you can go this far above the temperature or this far below a temperature and you are safe." Effectors are what changes the value of the variable is.
To explain this, blood pressure is probably the best example:
- Receptors detect an increase in blood pressure
- The Control Center tells the heart to slow down
- The blood pressure will decrease because of the decrease in the heart rate
The effector in this instance would be the heart, because it changed the variable to a normal value.
Other Negative Feedback Examples
We've done blood pressure, and we've covered temperature. More examples include the lack of food. Your body will slow down metabolism, allowing you to continue functioning, although the body is starving. This is why it's easy to lose a couple pounds when you're starving yourself, but it only lasts so long. Also, once you eat again, your body will speed up the metabolic process and you will gain the weight right back.
Positive Feedback Mechanisms
Positive feedback mechanisms are NOT homeostatic, and can lead to death. It's rarely found in the body. We'll use temperature again. Let's say you get a fever. Your body increasing the temperature until you die is the example of a positive feedback mechanism. That example is a bit unrealistic, but here's another one that can actually happen-
A person is stabbed, and is bleeding out. The receptors say "we need more blood, we don't have enough." The control center tells the heart, "Beat faster, we need to get more blood there." The blood keeps flowing out of the wound, and the receptors continue calling for more and more blood.
There are a few examples of positive feedback systems that do help the body such as birth. The baby is ready to pop, the uterus stretches and lets the body know that it's time for contractions. The uterus stretches more, and therefor, more contractions. Once the baby is born, the stretching ends, the contraction ends, and the stimulus is now ended.
That About Sums it Up
If I've forgotten anything, feel free to leave a comment. If you're an Anatomy and Physiology student, feel free to read some of my other articles to help get you started in your classes.