I know the basics of how pain works. I know the basics of the nervous system. I had a question, however, that hopefully somebody here can answer. Is there anyway to calculate pain relative to something else?
For instance, which would probably hurt more: dropping a 5kg weight on your foot from 3 meters or dropping a 7kg weight from 2 meters on your foot. The 5kg weight will have more velocity on impact but the 7kg weight is heavier... I know that there are many factors (where the weight lands exactly, angle of weight (any sharp sections), etc.), but I am assuming that everything is the same except the mass and height.
This is obviously something that I do not want to test (although maybe some masochist will test it out someday...), so I am hoping that there is a way to calculate this out...
Well, you could calculate the intensity and duration of force applied to the foot in each example, but that still might not clearly show which hurts more.
You could take it a step further, and calculate the amount of damage done by each, and the amount (and severity) of nerves being affected.
To really decide it though, you need to do this:
1: Gather a very large amount of people for a 'clinical study'. Tell them they'll be on national TV, and they'll come.
2: Randomly separate that group into two sections.
3: Drop each weight on the feet of each section, respectively. (Only one drop per person.)
4: Have each person rate their pain on a (more accurate) scale of 3 to 14.
5: See which section gave, on average, the higher numbers.
6: Make sure the outraged participants get news coverage, completing your bargain of getting them on national TV.
That's not calculation anymore, that's an experiment.
To calculate the intensity of pain, one would probably have to build a computational model of the foot (for example) with all the nerves and sensors in the right place. I'm not a biologist so I don't know what this would involve, but of course you can make your model as simple or as complicated as you want. In the most basic model, one would assume equal distribution of sensors among the foot and it would be sufficient to see how much force is applied on what surface area.
In a more realistic program, the code should contain the known theory of pain, iirc nerve response to applied force in this case, combined with a 'map' with positioned nerves, sensors, etc. It would then be possible to apply any force to any location of the foot and the program could calculate the response of the nerves.
In what units do we express pain? I'm thinking it would be related to the intensity (mV) and frequency of the pain signal. IIRC the intensity has a maximum value (this is biochemically dictated, you don't want 500 V potential difference over a membrane) and when that is reached stronger pain corresponds to a higher signal frequency, not to a higher intensity. But it's been a while for me.
^^ocalhoun: I thought of something like that but decided against it because I'd want to find a way to calculate it out without having to experiment (because dropping weights on people can do serious damage.
^^Arnie: That would be the best way, although very expensive. I was trying to think of a way that I could do it without having the knowledge or money to build an entire computer system.
Also, I was just thinking about something (that maybe some biologist here will know about)... Does more work on a system (like your foot) equal more pain? That still doesn't account for all of the variables (where exactly it lands, what angle, etc.) but it does include speed and mass...
Well pain is also relative to your state of mind, mood, awareness etc. So, I would think that if you want to calculate something like that one important factor (and probably more important than the amount of damage done to tissue or organs) is how the person perceives the pain sensation, which has to do with how that person is feeling at that moment and also past expriences coping (or not) with pain.
This effect of the "state of mind" you're referring to probably has its key origin in the working of neurotransmitters, chemicals in the nervous system that can inhibit or stimulate propagation of pain signals. Simply stated: when you're happy certain chemicals are present more than when you're sad, but it's actually a lot more complicated because there are a lot of chemicals involved and concentrations can vary much.
Including this factor in a computational model of pain perception would make the model more complicated but (if done correctly) also applicable for more situations. The model I described in my previous post stops at the point where the neurons in the foot transmit pain signals, while including neurotransmitters requires extending the simulated trajectory completely to the brains.
Whether or not one would choose to include such things in a model depends on what questions one aims to answer with the model. You don't just build a model for fun, you do it because you want to gain certain insight. But you also don't want to do more work than is necessary. In the example question this topic started with, "state of mind" is not a relevant factor so there would be no need to make the model overcomplicated. For answering the question we can probably start with a simple model that doesn't require a computer at all, but can be solved on paper by some guy from the maths department. Or actually this looks more like textbook physics.
