Homeostasis

What is homeostasis?

Homeostasis is a fundamental concept in the life sciences.

Homeostasis
Humans rely on homeostasis to keep their core temperature hovering around 98.6 degrees Fahrenheit, so that their bodies can maintain proper function.

Homeostasis is the ability to maintain a relatively stable internal state despite changes in the external environment. To process energy and ultimately survive, all living organisms, from plants to puppies to humans, must regulate their internal environment. If your blood pressure rises or your body temperature falls, for example, your organ systems may struggle to function and eventually fail.

WHY IS HOMEOSTASIS ESSENTIAL?
In the 1920s, physiologist Walter Cannon coined the term “homeostasis,” expanding on previous work by late physiologist Claude Bernard. Bernard described in the 1870s how complex organisms must maintain balance in their internal environment, or “milieu intérieur,” in order to live a “free and independent life” in the outside world. Cannon refined the concept and popularized homeostasis with his book “The Wisdom of the Body” (The British Medical Journal, 1932).

Cannon’s basic definition of homeostasis, hailed as a core tenet of physiology, is still used today. The term “homeostasis” is derived from Greek roots that mean “similar” and “a state of stability.” The prefix “homeo” emphasizes that homeostasis is not like a thermostat or cruise control in a car, which is fixed at one precise temperature or speed. According to a review published in the journal Appetite, homeostasis maintains important physiological factors within an acceptable range of values.

The human body, for example, regulates the internal concentrations of charged particles such as hydrogen, calcium, potassium, and sodium, on which cells rely for normal function. According to a 2015 review published in Advances in Physiology Education, homeostatic processes also maintain water, oxygen, pH, and blood sugar levels, as well as core body temperature (opens in new tab).

According to Scientific American, homeostatic processes occur constantly and automatically in healthy organisms (opens in new tab). Multiple systems frequently collaborate to maintain a single physiological factor, such as body temperature. If these safeguards fail, an organism may succumb to disease or even die.

HOW IS HOMEOSTASIS MAINTAINED?
Many homeostatic systems monitor the body for distress signals to determine when key variables are out of range. These deviations are detected by the nervous system and reported to a control center, which is frequently located in the brain. The control center then instructs muscles, organs, and glands to correct the problem. According to the online textbook Anatomy and Physiology, the continuous loop of disturbance and adjustment is known as “negative feedback”

The human body, for example, maintains a core temperature of approximately 98.6 degrees Fahrenheit (37 degrees Celsius). When the body becomes overheated, thermosensors in the skin and brain sound an alarm, triggering a chain reaction that causes it to sweat and flush. When the body is chilled, it shivers and reduces blood circulation to the skin. According to two NIH-funded studies, when sodium levels rise, the body signals the kidneys to conserve water and expel excess salt in concentrated urine (opens in new tab).

Animals’ behavior will also change in response to negative feedback. When we are overheated, we may, for example, remove a layer of clothing, move into the shade, or drink a cold glass of water.

MODERN HOMEOSTASIS MODELS
The concept of negative feedback can be traced back to Cannon’s 1920s description of homeostasis, which was the first explanation of how homeostasis works. However, many scientists have argued in recent decades that organisms can anticipate potential disruptions to homeostasis rather than reacting to them after the fact.

According to a 2015 article in Psychological Review, this alternative model of homeostasis, known as allostasis, implies that the ideal set point for a specific variable can shift in response to transient environmental changes . Circadian rhythms, menstrual cycles, and daily fluctuations in body temperature may cause the point to shift. According to a 2015 review published in Advances in Physiology Education, set points may also change in response to physiological phenomena such as fever or to compensate for multiple homeostatic processes occurring at the same time (opens in new tab).

“The set points themselves aren’t fixed,” said Art Woods, a biologist at the University of Montana in Missoula.

“This model enables anticipatory responses to potential disturbances at set points.”

According to a 2007 review in Appetite, the body secretes extra insulin, ghrelin, and other hormones in anticipation of a meal (opens in new tab). This preventative measure prepares the body for the impending influx of calories, rather than fighting to control blood sugar and energy stores in its wake.

Animals with the ability to shift set points can adapt to short-term stressors, but they may fail in the face of long-term challenges like climate change.

“For short periods of time, activating homeostatic response systems can be fine,” Woods said. However, they are not intended to last long.  “Homeostatic systems can fail catastrophically if pushed too far; thus, while systems may be able to handle novel climates in the short term, they may not be able to handle larger changes over longer time periods.”

Homeostasis
Homeostatic points can be adaptive. For example, in anticipation of a meal, the body secretes extra insulin, ghrelin and other hormones to prepare the body for the incoming food.

A HOMEOSTASIS “INFORMATION HYPOTHESIS”

Homeostatic systems may have evolved primarily to assist organisms in maintaining optimal function in a variety of environments and situations. However, some scientists believe that homeostasis primarily serves as a “quiet background” for cells, tissues, and organs to communicate with one another, according to a 2013 essay in the journal Trends in Ecology & Evolution(opens in new tab). According to the theory, homeostasis facilitates organisms’ ability to extract important information from their surroundings and shuttle signals between body parts.

Homeostasis has shaped life science research for nearly a century, regardless of its evolutionary purpose. Homeostatic processes enable plants to manage energy stores, nourish cells, and respond to environmental challenges, despite being mostly discussed in the context of animal physiology. Beyond biology, homeostasis is used as a framework to understand how people and machines maintain stability in the face of disruptions in the social sciences, cybernetics, computer science, and engineering.

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By Jumai

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