Homeostasis is the ability to maintain a relatively stable internal state that persists despite changes in the external world. All living organisms, from plants to puppies to humans, must regulate their internal environment in order to process energy and ultimately survive. If your blood pressure skyrockets or the body temperature for example, your organ systems may struggle to do their jobs and eventually fail.
Why is homeostasis important?
Physiologist Walter Cannon coined the term homeostasis in the 1920s, expanding on earlier work by the late physiologist Claude Bernard. In the 1870s, Bernard described how complex organisms must maintain equilibrium in their internal environment, or “internal milieu.”,“ to lead a “free and independent life” in the world abroad. Cannon honed the concept and introduced homeostasis to a popular audience through his book The Wisdom of the Body (British Medical Journal, 1932).
Cannon’s basic definition of homeostasis, recognized as a basic principle of physiology, is still used today. The term comes from Greek roots meaning “like” and “state of stability.” The “homeo” prefix emphasizes that homeostasis doesn’t work like a thermostat or cruise control in a car, fixed at one exact temperature or speed. Instead, homeostasis maintains important physiological factors within an acceptable range values, according to a review in the journal Appetite (opens in a new tab).
On the topic: Has the average human body temperature always been the same?
The Human body, for example, regulates the internal concentration of hydrogen, calcium, potassium, and sodium, charged particles that cells rely on to function normally. Homeostatic processes also maintain water, oxygen, pH and blood sugar levels as well as core body temperature, according to a 2015 review Achievements of physiological education (opens in a new tab).
In healthy organisms, homeostatic processes unfold constantly and automatically, respectively Scientific American (opens in a new tab). Multiple systems often work in tandem to maintain a single physiological factor, such as body temperature. When these measures fail or fail, the body can succumb to disease or even death.
How is homeostasis maintained?
Many homeostatic systems listen for distress signals from the body to know when key variables fall out of the proper range. The nervous system detects these abnormalities and reports to a control center, often located in the brain. The control center then directs the muscles, organs, and glands to correct the disorder. The constant cycle of disturbances and adjustments is known as “negative feedback,” according to an online textbook Anatomy and physiology (opens in a new tab).
For example, the human body temperature is maintained at about 98.6 degrees Fahrenheit (37 degrees Celsius). When you overheat, thermosensors in the skin and in the brain sound the alarm, initiating a chain reaction that causes the body to sweat and flush. When the body cools down, it reacts with chills and weakness blood circulation to the skin. Likewise, when sodium levels jump, the body signals the kidneys to conserve water and excrete excess salt with concentrated urine, according to two Research funded by the NIH (opens in a new tab).
Animals will also adjust their behavior in response to negative feedback. For example, when overheatingwe can shed a layer of clothing, move into the shade, or drink a glass of cold water.
Modern models of homeostasis
The concept of negative feedback dates back to Cannon’s description of homeostasis in the 1920s and was the first explanation of how homeostasis works. But in recent decades, many scientists claim that organisms are able to anticipate possible disturbances in homeostasis, rather than reacting to them after the fact.
This alternative model of homeostasis, known as allostasis, suggests that the ideal set-point for a particular variable can change in response to transient changes in the environment, according to a 2015 paper. Psychological review (opens in a new tab). The point can shift under the influence of daily rhythms, menstrual cycles or daily fluctuations in body temperature. Setpoints may also change in response to physiological events, such as fever, or to compensate for multiple homeostatic processes occurring simultaneously, according to a 2015 review. Achievements of physiological education (opens in a new tab).
“The set points themselves are not fixed, but can exhibit adaptive plasticity,” said Art Woods, a biologist at the University of Montana in Missoula. “This model allows for prompt response to upcoming potential breaches to set points.”
For example, while waiting for a meal, the body releases excess insulin, ghrelin and other hormones. Review 2007 in Appetite (opens in a new tab). This preventative measure prepares the body for an influx of calories, rather than struggling to control blood sugar and energy stores.
The ability to change set-points allows animals to adapt to short-term stressors, but may fail in the face of long-term challenges such as climate change.
“Activating homeostatic response systems can be good for short periods of time,” Woods said. But they are not designed to last long. “Homeostatic systems can fail catastrophically if pushed too far; therefore, while systems may be able to cope with the new climate in the short term, they may not be able to cope with large changes over longer periods of time.’
“Information hypothesis” of homeostasis
Homeostatic systems may have primarily evolved to help organisms maintain optimal function in a variety of environments and situations. But according to a 2013 essay in the journal Trends in ecology and evolution (opens in a new tab), some scientists theorize that homeostasis primarily provides a “quiet background” for communication between cells, tissues, and organs. The theories states that homeostasis makes it easier for organisms to extract important information from the environment and transmit signals between body parts.
Regardless of its evolutionary purpose, homeostasis has shaped research in the life sciences for nearly a century. Although homeostatic processes are mainly discussed in the context of animal physiology, they also enable plants to manage energy stores, feed cells, and respond to environmental challenges. In addition to biology, the social sciences, cybernetics, and computer science use the technique of homeostasis as a basis for understanding how humans and machines maintain stability despite disruptions.
Additional resources
Check out some helpful graphics on homeostasis from Khan Academy (opens in a new tab). Learn how homeostasis affects human physiology Accelerated course (opens in a new tab). Watch this video from Amoeba sisters (opens in a new tab) to learn more about negative feedback.
Originally published on Live Science.
