What is Allostasis? - Definition, Allostatic Load & Example

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

In this lesson, you're going to learn about more than one possible definition of allostasis. Then, you'll learn about the definition of allostatic load. Both concepts will be explained with examples in mind.

What is Allostasis?

Allostasis is a bit of an oddball concept. It can be defined as stability through change or as the process for actively maintaining homeostasis. But there's a problem with either definition in that both can be seen as really referring to misunderstandings or misrepresentations or misapprehensions of a concept known as homeostasis. Homeostasis is a state of dynamic equilibrium maintained within a biological system in response to external and internal stressors or changes.

But this lesson isn't about the nitty gritty comparison between allostasis and homeostasis and why they can really be seen as the exact same thing. Instead, we'll explain allostasis in more detail, explain a concept known as allostatic load, and provide a couple of examples to help you understand both concepts.

More on Allostasis

OK, so let's get to the more detailed part of allostasis. To some people, allostasis refers to the processes of homeostasis, like how the body changes the pH of its fluids or how the body regulates blood pressure to maintain a relatively steady internal environment. So, while homeostasis is the endpoint, a state of dynamic equilibrium, allostasis is the process by which the body reaches that endpoint.

For others, allostasis is a bit different. Allostasis is seen by some as the way by which the body varies all of its parameters (e.g., pH, blood pressure, heart rate, temperature) in order to match them to external demands (e.g., temperature, being asleep or awake, etc).

Example

As an example, we can think of heart rate and blood pressure. Let's say that you are sleeping. Your heart rate and blood pressure are going to be low. As soon as you get up in the morning and go for a jog, your heart rate and blood pressure will go up. The fact that your body varied its parameters to match the new environment (jogging vs. sleeping) is an example of allostasis.

Allostatic Load

Another concept related to allostasis is allostatic load. Allostatic load refers to the strain a biological system experiences as a result of its attempt to maintain homeostasis. Excessive allostatic load would thus wear down the body and predispose to accelerated aging or one illness or another.

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