There are a lot of things going on in the human body that no one thinks about until they go awry. This is thanks to homeostasis (from the Greek homeo, meaning "similar," and stasis, meaning "stable"), the body's natural tendency to keep things delightfully status quo, even in the face of major changes or outside influences on one part of it. Regulated largely by the endocrine and nervous systems, homeostasis is a combined effort across many bodily levels, from organ to tissue to organism level to keep things in balance.
When homeostasis is compromised it seriously throws things out of whack, causing everything from mental disturbances to mild discomfort to death. So when the body is presented with an abnormal stimulus that threatens to do harm to the delicate internal balance, such as major stress, blood loss or toxin exposure, homeostasis shifts into overdrive to fight back. Here are five prime examples of homeostasis doing its finest work:
1. Internal Body Temperature
It's common knowledge that a normal temperature is 98.6 degrees Fahrenheit, or 37 degrees Celsius. People are warm-blooded, which means that external factors like the sun don't affect us in the same way that they do cold-blooded creatures, like snakes. Still, body temperature can fluctuate from time to time, usually signaling a problematic infection or virus. If this thermoregulation disruption doesn't resolve itself or isn't handled properly, it can actually result in reduced blood flow and possibly multiple organ failure.
So, when the body senses problematic pathogens (like during an illness) it responds by releasing its own collection of pyrogens, which actually cause the temperature to go up. By doing so, the invaders can't reproduce, thus allowing antibodies and enzymes to better fight off the infection. Once that happens, sweet homeostasis is restored and the body temperature goes back to normal.
2. Blood Pressure
When blood pressure is consistently too high it puts huge strain on the heart and blood vessels, ramping up risk for stroke and heart attack. It's also none too kind to the kidneys and can even contribute to dementia risk. When blood pressure dips too low, it can cause fainting, dizziness and even more severe problems.
Clearly, maintaining a steady, healthy blood pressure is a pretty important goal. When blood vessels detect a major fluctuation in blood pressure they ping the hypothalamus in the brain. The hypothalamus then alerts the heart, kidneys and blood vessels to adjust appropriately to re-regulate blood pressure. Unfortunately, sometimes homeostasis can't keep pace with blood pressure problems, which are often caused by ongoing lifestyle issues like inactivity, being overweight and drinking too much alcohol.
Blood glucose, known more casually as blood sugar, is critically important to body function and overall health. From a homeostasis perspective, the brain, liver, pancreas and intestines all work in concert to keep just the right balance of hormones and neuropeptides to keep blood glucose in check. The pancreas also has to accurately secrete insulin, which effectively lowers sugars.
As with blood pressure, there is again only so much homeostasis can do once the pancreas and other organs are compromised. People with various types of diabetes have a harder time regulating glucose, and instead have to implement anti-diabetic drugs and treatments to return things to the status quo.
4. Water Balance
About 60 percent of the human body is water. Nature's juice has some seriously important jobs, including regulating body temperature through sweating, flushing out body waste via urine, lubricating joints, delivering oxygen and aiding digestion, among many others. That said, there can definitely be too much of a good thing, so it's best to keep water levels from getting out of whack. When water levels build up too much it's known as fluid retention, or edema. This can sometimes be a symptom of kidney or heart failure, although there are plenty of other less serious causes.
Under regular, non-emergent circumstances, homeostasis gets the kidneys involved to regulate water levels. If there's too much water floating around, the kidneys shift gears to dilute urine, thus getting rid of extra water. If dehydration is the issue the kidneys can actually conserve water to prevent catastrophe.
5. Blood Flow
There's only so much blood to go around, so homeostasis makes sure that blood is where it needs to be at the right time. Think about how exercising starts off slow, but ramps up after a minute or two. That's because the cardiovascular system gets wind of the extra effort and then re-routes blood to the muscles, lungs and heart. However, after a big meal the digestive system needs a little TLC, so more blood is sent there to balance things out. Whenever tissues need more blood to get the job done, homeostasis provides the supply, keeping the bodily scale balanced and in harmony.