Homeostasis can be defined as a property of an organism or system that helps it maintain its parameters within a normal range of values.
It is key to life, and failures in homeostasis can lead to diseases like hypertension and diabetes.
Definition of Homeostasis
Homeostasis is a key concept in understanding how our body works. It means keeping things constant and comes from two Greek words: ‘homeo,’ meaning ‘similar,’ and ‘stasis,’ meaning ‘stable.’ A more formal definition of homeostasis is a characteristic of a system that regulates its internal environment and tends to maintain a stable, relatively constant, condition of properties.Homeostasis is happening constantly in our bodies. We eat, sweat, drink, dance, eat some more, have salty fries, and yet our body composition remains almost the same.
If someone were to draw your blood on ten different days of a month, the level of glucose, sodium, red blood cells and other blood components would be pretty much constant, regardless of your behavior (assuming fasting before drawing blood, of course).No matter how much water you drink, your body doesn’t swell up like a balloon if you drink tons, and it doesn’t shrivel like a raisin if you drink very little. Have you ever wondered about this? Somehow, our bodies know how much fluid we need to keep, and then maintain a constant level regardless of how much water we drink.This maintenance of body size is an example of homeostasis. And we don’t even have to think about it for this to happen! Aren’t our bodies amazing?There are several other examples of homeostasis.
For example, our concentration of salts and glucose (sugar) is constant; our body temperature is usually around 37 degrees Celsius (98.6 degrees Fahrenheit); the amount of blood in our bodies is about 5 liters, the osmolarity (number of solutes) of our blood remains about 300mOsm. The normal value of a physiological variable is called its set point.
How is Homeostasis Achieved?
So, how does our body regulate all these variables and compensate for changes in the environment? Well, it turns out we have tons of sensors in our body that monitor the temperature, salt composition of blood, blood pressure, osmolarity, and other things. These detectors signal the brain, the control center, when some value has deviated from normality and trigger compensatory changes that will try to restore that value to normal.
For example, imagine that you go outside and it’s really hot. This will start changing your body temperature. Temperature sensors in our brain monitor body temperature, and if it starts rising (moving away from its supposed set point), this activates an effector tissue or organ that will help bring the temperature back to its set point. For example, if your body temperature rises, then you start sweating. This is a compensatory response by your body to lower your temperature back to normal.The control center, sensors, and effector together form what is known as a control system. Control systems are everywhere; a thermostat that regulates room temperature is a classic example of a control system.
Control systems that tend to reduce the difference between the desired value of a variable and the observed value are called negative feedback systems, or error correction systems.Here is a second example: Imagine that you drank lots of water. This water will go into your blood, increase its volume, and thus raise your blood pressure. This will activate baroreceptors (pressure receptors) in your blood vessels that will signal the brain to release hormones that will act on your kidneys to promote the elimination of water through urine. Thus, you will find yourself suddenly going to the restroom more often, which will reduce the amount of water in your blood, and thus lower your blood pressure.
And there you are; good as new!
Disease as Failure of Homeostatic Mechanisms
Homeostasis is so important that, when it fails, it usually results in serious bodily damage. For example, the disease diabetes is a failure in the homeostasis of blood sugar. People with diabetes tend to have very high levels of sugar in their blood right after they eat and then very low levels in between meals. As a result of this lack of sugar homeostasis, diabetic patients develop eye problems, leg problems, kidney problems, etc.
Individuals with diabetes have to carefully monitor their blood sugar levels and their diet, while those without diabetes don’t have to worry about it because their body does all the work for them and keeps sugar levels constant.
Homeostasis is a key concept in understanding how our body works. It means keeping things constant and comes from two Greek words: ‘homeo,’ meaning ‘similar,’ and ‘stasis,’ meaning ‘stable.’ A more formal definition of homeostasis is a characteristic of a system that regulates its internal environment and tends to maintain a stable, relatively constant condition of properties.
The normal value of a physiological variable is called its set point. The control center, sensors, and effector together form what is known as a control system. Control systems that tend to reduce the difference between the desired value of a variable and the observed value are called negative feedback systems, or error correction systems.
Key Points on Homeostasis
- Homeostasis is constantly happening in our bodies
- Homeostasis is achieved through your body’s control system
- Disease is an indicator of a failure in homeostasis
After you have finished, you should be able to:
- State what homeostasis is
- Explain why homeostasis is important for organisms
- Describe how homeostasis is attained in the body