What is the Difference Between Allostasis and Homeostasis

The main difference between allostasis and homeostasis is that allostasis is the process of maintaining homeostasis, whereas homeostasis is the state of steady internal physical and chemical conditions maintained by living systems. 

Allostasis and homeostasis are two processes related to physiological regulation. Homeostasis is the ability of a biological system to maintain a dynamic internal equilibrium according to the changes in the internal or external environment. Allostasis, on the other hand, is the process of maintaining homeostasis 

Key Areas Covered 

1. What is Allostasis
     – Definition, Process, Importance
2. What is Homeostasis 
     – Definition, Process, Importance
3. What are the Similarities Between Allostasis and Homeostasis
     – Outline of Common Features
4. What is the Difference Between Allostasis and Homeostasis
     – Comparison of Key Differences

Key Terms 

Allostasis, Homeostasis, Negative Feedback Loop, Physiological Regulation, Positive Feedback Loop

What is Allostasis 

Allostasis is a process of regulation responsible for achieving stability through change. Sterling and Eyer coined the term allostasis in 1988. The main purpose of the process is to re-establish stability in response to a challenge. Also, this can be done by means of alteration in HPA axis hormones, the autonomic nervous system, cytokines, and other systems. Moreover, allostasis is responsible for compensating many problems, including heart, kidney, and liver failure.  

Furthermore, a key difference between allostasis and homeostasis is that allostasis is about a more dynamic balance when compared to homeostasis. Therefore, allostasis uses a collection of physiological reactions to balance the condition. But, in homeostasis, the balance is only in a single point such as blood oxygen level, blood glucose level, blood pH, etc. 

What is Homeostasis 

Homeostasis is the state of maintaining a steady physical and chemical environment inside a living organism. Therefore, it keeps all the conditions of the body in their optimal values. Some examples of such conditions are blood sugar level, body temperature, fluid balance, pH of the extracellular fluids, ion concentration, etc. 

Figure 1: Body Temperature is Regulated by Negative Feedback

Moreover, the maintenance of homeostasis is by different feedback mechanisms. Generally, there are two types of feedback mechanisms called positive feedback loops and negative feedback loops. Basically, most of the conditions are balanced by negative feedback loops. They draw the changes to their reverse direction to get the values back to the normal values. On the other hand, positive feedback loops amplify the stimulus to get a strong action. For example, oxytocin stimulates uterine contractions in an increasing pattern at childbirth. 

Similarities Between Allostasis and Homeostasis 

• Allostasis and homeostasis are two processes related to the physiological conditions of an animal. 
• Moreover, they help to maintain a constant internal environment in response to changes in either internal or external environment. 

Difference Between Allostasis and Homeostasis 

Definition 

Allostasis refers to the process by which a state of internal, physiological equilibrium is maintained by an organism in response to actual or perceived environmental and physiological stresses. But, homeostasis refers to the tendency towards a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes. Thus, this is the fundamental difference between allostasis and homeostasis.

Correspondence 

Furthermore, allostasis is the process of maintaining homeostasis while homeostasis is the state of steady internal physical and chemical conditions maintained by living systems. 

Number of factors to Balance 

Also, another difference between allostasis and homeostasis is that allostasis regulates a number of conditions together while homeostasis regulates a single condition of the body at a time.

Importance 

Moreover, allostasis is responsible for achieving stability through changing while homeostasis is the ability of a biological system to maintain a dynamic internal equilibrium according to the changes in the internal or external environment. 

Conclusion 

Basically, allostasis is the process of maintaining homeostasis. On the other hand, homeostasis is the state of the steady internal environment in a living organism. Generally, allostasis maintains the stability of the internal environment by changing the conditions. Therefore, the main difference between allostasis and homeostasis is the importance of the process. 

References:

1. Ramsay, Douglas S, and Stephen C Woods. “Clarifying the roles of homeostasis and allostasis in physiological regulation.” Psychological reviewvol. 121,2 (2014): 225-47. doi:10.1037/a0035942.

Image Courtesy:

1. “105 Negative Feedback Loops” By OpenStax (CC BY 4.0) via Commons Wikimedia