The Applications Of Process Control In The Human Body
What people do in industry is really a mimicry of what is going on in our body.
(Image source: https://instrumentationforum.com/t/basics-of-control-loop-in-p-id/7079)
By virtue of the education background that I have been brought up in, I am a chemical engineer by trade. I have dabbled in chemistry, biochemistry and biochemical engineering (which is more relevant to what this Substack newsletter is all about!), but I am a lecturer in chemical engineering by day.
One of the courses that I have previously operated is about process control, or basically, how we use technical equipment to manipulate a chemical process to optimise the production rates of a desired product.
And of course, we’ll look at how that mimics the biochemical operations within our body as an analogy too.
In the image above, we can see a few things:
There is a tank containing liquid. There is an inlet stream feeding liquid into the tank, and an outlet stream draining liquid from the tank.
A control valve regulates the flow rate of the outlet stream - it acts as the final control element.
A level controller sends a signal to the control valve to determine how open or how closed the valve should be - this regulates the flow rate of the outlet stream.
The intensity of the signal being sent to the control valve from the level controller is determined by the information that the level transmitter is feeding to the level controller. This level transmitter measures the height of the liquid level in the tank. The level controller is programmed with a specific set point in mind: to maintain the liquid level in the tank at that set point value.
Therefore, if the liquid level in the tank were to fall below the set point value, the level transmitter would send a signal to the level controller indicating that the liquid level is below the set point, and the level controller would then send a signal to the control valve to close up and reduce the flow rate of the outlet stream.
Conversely, if the liquid level in the tank were to be greater than the set point value, the level transmitter would send a signal to the level controller indicating that the liquid level is above the set point, and the level controller would then send a signal to the control valve to open up and increase the flow rate of the outlet stream.
In that way, the level controller is actively working to ensure that the liquid level remains as close to the set point value as possible.
All these elements come together to form what is known as a control loop.
In fact, there are various different elements that we can control in various operations that exist around the world. Temperature controls for regulating air-conditioning and heating systems also function on such control loops, just that it would be regulating the temperature in an enclosed room rather than the liquid level in a tank, for instance.
Now that the technicalities are out of the way…
Let’s look at how our body operates with process control.
A well controlled process is absolutely boring. We might not even notice it at all, because everything’s just operating so smoothly, and the boring stuff rarely ever gets noticed.
Ever wonder how our bodies regulate or control our internal temperatures, though?
We don’t really notice it… but we do notice when we get a fever.
And of course, the days when we do have a flu are worse…
We don’t really notice it when we don’t have a flu… but those muscle aches and the runny nose can be extremely annoying when we do have one!
What about when we sustain an injury?
We don’t really notice it when we don’t have an injury… but a fractured foot or a severe burn can be a world of pain. Personally, I’m dealing with tight hips, an annoying psoas muscle, and… it’s annoying, to say the least. Foam rolling, stretching and myofascial release does help, but the problem ain’t gonna disappear overnight.
When we fall ill… Let’s look at a fever.
It’s the body’s way of telling us that something has gone dysregulated, or that the control of a certain process operation isn’t as good as it ought to be.
In the case of a fever, we’re looking at an overexpression of pyrogenic substances that cause our bodily temperatures to overshoot beyond a “normal” range.
In the case of a runny nose, we’re looking at an overexpression of histamines, which triggers mucus hypersecretion within the nose.
In the case of an injury, we’re looking at the effects of an overexpression of pro-inflammatory cytokines that are necessary for signalling the onset of internal repair works within the body.
As we can see, these examples all relate to an overproduction of something.
Of course, there are other situations that lead to an underproduction of some other thing, and that isn’t that great for the body either.
in a process control loop like we have seen above, a liquid level that deviates from the set point value can be pinned on many different probable sources:
The level transmitter is reading the wrong liquid level heights and sending the wrong signals to the level controller.
The level controller isn’t closing or opening the control valve appropriately.
The control valve itself has a problem closing or opening appropriately.
Or what if there were a sudden flood at the inlet? The control loop system may not be able to respond in time to match that disturbance.
Our body temperature, for instance, is kept under control at 36.5–37.5°C (97.7–99.5°F). We don’t feel like there’s anything wrong with us when we wake up with that kind of body temperature.
However, there can be many different reasons why our body temperature regulation goes out of whack, which then results in the symptom of a fever development.
When there is an invasion of the body by undesirable foreign elements (whether bacteria, viruses or whatever), the immune system raises an alarm in the form of pro-inflammatory cytokine signalling. Various immune cells can produce different cytokines in response to the invasion or threat.
The problem is, we want the response to be just right.
When the intensity of the response signal is too low, we’d find that the response rate towards the elimination of the threat is insufficient, and people could take a longer time to recover from dealing with that threat.
When the intensity of the response signal is too high, we’d be producing too much of the pro-inflammatory cytokines within the blood, and that’s how infections can result in the development of fevers - because they’re pyrogenic.
That overproduction of pro-inflammatory cytokines isn’t “just right” because we’d feel feverish, sluggish, and totally out of our element.
Unfortunately, we’re not doing ourselves any favours.
The modern day lifestyle is not conducive towards the biochemical inflammatory signalling pathways within our body:
The major pro-inflammatory and pyrogenic players in our bodies include interleukin 1-beta (IL-1β), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF-α).
The body’s immune cells can produce them in significantly greater amounts during an invasion, and that’s when the body’s temperature can rise, if these pyrogens are produced at sufficient quantities - we’d be looking at a case of acute inflammation there.
However, subscribing to the tenets of a suboptimal lifestyle also does open up avenues for the production of these pro-inflammatory cytokines to become dysregulated.
When we’re perpetually stressed or we’re perpetually sleep deprived, our adrenal glands tend to release more of the fight-or-flight hormones (epinephrine and norepinephrine) into the blood:
These 2 hormones help to increase the activity of the pro-inflammatory nuclear factor kappa B (NF-κB) signalling pathway in the body, which is responsible for inducing the synthesis of those darned pro-inflammatory pyrogens.
And if the NF-κB pathway is dysregulated, then what would happen to the control loop that regulates inflammation within our body?
Getting our own bodies to regulate the production processes of so many different biochemicals can be a pretty tedious operation to do indeed. But that’s the perfection that we do actually have to strive for if we do seek to be in optimal health!
Do feel free to refer to:
If you would like to see how the consumption of medications for illnesses can affect how the control loop functions.
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