Homeostasis, stress, and adaptation
Over the past few weeks we’ve been exploring the idea of using an evolutionary framework to guide our efforts to get lean, strong, and healthy AF.
This framework is based on the following concepts:
- Our bodies comprise trillions of cells, operating in a coordinated effort according to the genetic instructions dictating their respective functions.
- Genetically, we as a species are all much more similar than we are different.
- The process of natural selection shaped our genetic makeup over millions of years, and we’re not that much different from our pre-agricultural ancestors.
- There’s a correlation between the rise of chronic disease, the decline of physical health, and the relatively rapid changes brought about by modernization of our environments and lifestyles since the dawn of agriculture.
- We might examine the differences between our pre-agricultural and our current environments and lifestyles to determine what steps we might take to pursue optimal health and wellness.
The next concepts we’ll explore to strengthen this framework are those of homeostasis, stress, and adaptation.
In the context of the evolutionary framework, the most successful genes would be those that express for traits and behaviors that promote survival of the organism long enough to reproduce and ensure that its offspring survives to do the same.
Every single one of our cells, all of which work together in a coordinated effort to ensure the survival and replication of our genes, are only able to perform their specific tasks when certain conditions are maintained.
Examples of such conditions include (but are certainly not limited to) temperature, local acidity or alkalinity, salinity, hydration, and energy availability.
Fortunately, we’ve got a variety of sensory and feedback loops built into our physiology to regulate these conditions.
For example, we experience thirst, hunger, fatigue, heat, cold, or pain to signal that action is necessary to correct conditions such as dehydration, low energy status, injury, or hostile environmental conditions.
We have seemingly simple processes such as sweating, for regulating body temperature, and seemingly more complex processes like inflammation and blood coagulation for promoting tissue regeneration and repair.
A dude named Walter Cannon coined the term, “homeostasis” — from the Greek words for “same” and “steady” — to describe concept of how the human body works to maintain these conditions for optimal function.
Nearly everything we do might be thought of as an effort to reach or maintain homeostasis — the maintenance of conditions necessary for survival and reproduction.
We commonly think of stress as being a state of mental or emotional overwhelm, usually as a result of work deadlines, lack of financial security, or problematic relationships.
However, stress might be better thought of as a state in which our bodies experience or perceive a deviation from homeostasis, indicating a threat to survival and/or reproduction.
Consider “stressful” situations such as financial insecurity — which is at its core a reflection of lack of resources necessary for maintaining shelter, food, and water — or relational problems — which might indicate a threat to reproductive success in the case of traditional sexual relationships, or general security in the case of familial or communal relationships.
Any condition that to our bodies interpret as a deviation from homeostasis — or a threat to survival or reproduction — might be called a “stressor”.
Similar to how we might respond to the stressors of financial insecurity or relational problems by taking action to correct those conditions, our bodies have innate mechanisms in place for addressing states of physiological stress in which there’s been a deviation from homeostasis.
Consider hunger and energy regulation, for example.
As various organs and systems utilize circulating blood glucose and fatty acids, an area of our brain called the hypothalamus senses a drop in circulating energy substrates and signals the pancreas to release a hormone called glucagon.
Glucagon then tells the liver and fat cells to release their glycogen (the stored form of glucose) and triglycerides (the stored form of fatty acids) into the blood stream to restore levels back to baseline.
Under more demanding conditions, the adrenal glands might release epinephrine to signal the muscles to mobilize their glycogen stores — or even amino acids — for utilization.
In the same vein (no pun intended), our bodies release a hormone called ghrelin to stimulate hunger after periods without food or even at times of normal feeding.
After we eat, digest, and assimilate our food, blood glucose and fatty acid concentrations might rise above baseline, signaling our hypothalamus to prompt the pancreas to release the hormone insulin, which in turn signals our liver, fat cells, and muscles to stop utilizing their energy stores and start replenishing them with the substrates available from the blood stream.
These are by no meant to serve as a comprehensive overview of energy status regulation, but to serve as examples of mechanisms through which our bodies maintain homeostasis in response to a stressor.
Our bodies don’t only respond to stressors in ways that maintain homeostasis in the short-term — as is often the case with eating and energy availability — but also in ways that promote a better ability to maintain homeostasis in the future.
When we lift weights, for example, we use certain neural pathways to perform specific movements, induce minor trauma to the involved muscle cells, increase heart rate to supply nutrients and oxygen to the systems involved through the bloodstream, and deplete glycogen and fat stores to fuel motion under load.
In response, our body not only returns to baseline by replenishing spent glycogen stores in the liver and muscles, but also encourages long-term adaptation by encouraging rest through the production of metabolites we interpret as fatigue, strengthening the neural pathways involved to improve movement proficiency, and rebuilding the muscles and heart stronger than they were previously.
In this case, training serves as a stressor, and all of the ensuing physiological effects — encouraging rest, glycogen replenishment, better movement proficiency through neural pathway development, and strengthening the muscles and heart — not only restore homeostasis, but also develop the systems involved to better handle the same (or similar) stressor in the future.
Each time we train, the effect may be marginal, but repeated consistently over and extended period of time, we might start to see noticeable changes in our muscle mass, strength, and movement proficiency.
The same concept might be applied to how we get chicken pox as a child and then never again as an adult.
When the varicella zoster virus — responsible for chicken pox — is introduced to the body, the immune system responds by pumping out specialized cells to neutralize the threat.
Once the threat’s been taken care of, some of these cells hang around and are available to respond to future exposures to the virus before it’s able to develop into full-blown chicken pox.
Again, these are not meant to serve as comprehensive overviews of these complex systems, but rather to provide general examples of how our bodies are able to adapt to certain stressors to better handle them in the future.
Our bodies work optimally when certain conditions are met, and have a variety of mechanisms in place to maintain these conditions, or homeostasis, in an effort to maximize chances of survival and reproduction.
Threats to, or deviations from, homeostasis come in a variety of shapes and sizes and can be called “stressors”.
We’re not only able to respond to stressors to restore homeostasis in the short-term, but also to adapt over time to better handle similar stressors in the future.
What we didn’t discuss is how things might go wrong with this whole stress-response thing, especially when the conditions necessary for recovery and adaptation aren’t met.
We’ll have to explore these additional considerations in future posts, however, so for now you might start asking yourself a couple of questions.
“What stressors are currently contributing to (or detracting from) my own pursuit of health and fitness?”
“What effects might these stressors be having on my efforts to maintain a lean, strong, healthy body?”
Until next time, have a most excellent day!
Originally published at https://coachroba.com on April 15, 2018.