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Medical Pain in the peripheral nervous system

  1. Jan 21, 2009 #1
    To my (limited) understanding, the peripheral nervous system sends messages of pain in the form of electrical impulses to the brains. But what's the difference between signals of extreme pain and mild pain/touch?
     
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  3. Jan 21, 2009 #2

    Monique

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    Well, what is the difference between looking at a dim light and an ultra-bright light. The latter will make you squint your eyes: it is a matter of the amount of stimulation. You have different receptors for different types of information: the nocireceptor senses injury and is thus responsible for feeling pain, you also have mechano- and thermoreceptors.

    The introduction of this review is interesting (about the difference between non-painful and painful sensory stimuli): Peripheral pain mechanisms.
     
  4. Jan 21, 2009 #3
    I'm interested in the actual signal that travels, like it's waveform, amplitude, phase etc? So that brains know that this is serious pain, output a mighty roar from mouth. :smile:

    I was looking for a bit (100%) cheaper article.
     
  5. Jan 21, 2009 #4

    Monique

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    First, there is a threshold that needs to be crossed before the nocireceptor starts to fire a signal. When there is sufficient stimulus, an action potential is created: the membrane of the neuron depolarizes (the voltage increases), the voltage peaks after which you get a hyperpolarization and a refractory period. The action potential spreads to the adjacent membrane, so that it can travel along the axon. The refractory period ensures that the signal can only travel in one direction, once the membrane has recovered it can fire again. The neuron can either be slightly excited giving a sparse signal, or strongly excited giving a continuous signal. I hope that addresses your question.
     
    Last edited: Jan 22, 2009
  6. Jan 21, 2009 #5
    Wikipedia is free:

    http://en.wikipedia.org/wiki/Neuron
     
  7. Jan 22, 2009 #6

    somasimple

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    Nociception isn't pain. Nociception is the message that is sent to brain.
    Pain is created only by brain.

     
  8. Jan 22, 2009 #7
    One cause of a huge variety of symptoms, including pain, that appear to have no pathophysiological cause, and which can be misdiagnosed as psychological, is Simple Partial Seizures:

    http://emedicine.medscape.com/article/1184384-overview

    Many Simple Partial Seizures are restricted to such small and/or deep portions of the brain that they aren't picked up by surface electrodes in an EEG, (which makes their misdiagnosis as psychological even more likely):

    http://www.ncbi.nlm.nih.gov/pubmed/3137487


    From Somasimple's quote:
    Therefore: I don't agree with the characterization of pain as a "psychological" experience in all cases. It would, by this author's logic, be accurate to say that our experience of heat and cold are always "psychological" as well. At the same time it is accurate to observe there is no dedicated "pain" signal; that a neutral signal's conversion to a perception of pain takes place in the brain, that conversion is a neurological, and not a psychological, event. The same neurological event can be triggered by means other than the normal stimulus (eg: simple partial seizure, trigeminal neuralgia), without it becoming a psychological event. The word "psychological" conotes emotional interpretation in the context of personal history.
     
  9. Jan 22, 2009 #8
    Ok, so the voltage (amplitude) of the signal is higher for extreme pain than for slight pain. Now the second question is that, why is it so hard to reconnect nerves when they have been cut? If they only acts as conductors for electricity, why isn't it possible to reconnect them with any conducting material?
     
  10. Jan 22, 2009 #9
    Axons don't work the same way as a conductor in an electric circuit. How much do you know about conventional electric circuits? It's hard to explain the difference without knowing how much you already know about either.
     
  11. Jan 22, 2009 #10
    I know a lot (almost all) about electric circuits, but very little of axons.
     
  12. Jan 22, 2009 #11

    Monique

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    No, it is the number of pulses that are generated by the neuron.
     
  13. Jan 22, 2009 #12

    turbo

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    I can attest to this. Years ago, I suffered a mild stroke due to some prescription medication that sent my heart into atrial fibrillation. A small clot made its way to my brain-stem and the damage caused me to lose temperature sensation in my right leg AND to cause a constant severe burning sensation in my right foot. My neurologist said that even if my right leg was amputated due to some severe injury or disease, I would still experience this pain for the rest of my life. Neuropathic pain is not fun at all - it can't be lessened with pain-killers, etc.
     
  14. Jan 22, 2009 #13
    What I was thinking, that is if have understood this nerve thing correctly, was to cut a nervous pathway and put a microchip in between two axons to some point where the nerves are bundled (like shoulder etc.). The chip wouldn't have to be physically embedded to the tissue, but conductors to the axon membranes would be needed. Then program the chip so, that it would filter out extreme pain coming from the arm (i.e. reduce the amount of pulses heading to brains) without the need for brain dissolving medication. It would be a very simple to make such a chip and when mass produced the price would easily be less that $10. Best part is that it could be programmed in any way the patient wants. This was obviously a simplified case, since there must be a few of those pathways, but the principle should apply.
     
  15. Jan 22, 2009 #14

    somasimple

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    Nerves use ions that have electric consequences but a microchip is purely electric, far from the functioning of a nerve that have many ways to change its behavior.
    And pain is not an incoming stimulus but a brain response to noxious (or considered as) stimulus.
     
  16. Jan 22, 2009 #15
    If nerves have electric consequences, they can be integrated with electric circuits.

    However, I don't quite understand that stimulus thing. How can the brains know if you hide your hand and someone/thing touches one finger? There has to be some kind of sensory input coming to brains. All one has to do is to identify which signal is noxious and filter it out.
     
  17. Jan 22, 2009 #16
    The point is that you can't simply splice any old conductor into an axon.

    I'm assuming you understand ions and cations. The electrical activity of nerves and neurons is based on actual physical motion of these, especially cations, rather than the EMF of conventional electricity based on electrons.

    To understand this, you need to take some time to read up on the basics of action potentials. Maybe Monique ot Soma know a good site.
     
  18. Jan 22, 2009 #17
    How about a new one? :smile: My purpose is not to make an axon, only something that can interface with axons.

    There is only one (known) kind of electricity in the universe. It involves the presence and flow of electric charge. There is no conventional and unconventional electricity. It's either electricity or it is something totally different.

    Apparently ion is a general category for atoms or molecules that have gained or lost electron(s). Ions have two subcategories: Anion which has more electrons than protons and cation which has less electrons than protons. Hence both of these have an electric charge of different polarity and are well in the realm of what you call conventional electricity.

    Now looking at Wikipedia, you can see a picture of membrane voltage. I can't find any explanation why it would be different from other kinds of voltage measurements. For example look at the voltage clamp picture in Electrophysiology -article.

    http://en.wikipedia.org/wiki/Action_potential
    http://en.wikipedia.org/wiki/Electrophysiology
     
  19. Jan 22, 2009 #18
    If I said a Stirling engine is not the conventional heat engine powered by exploding gases, would you object saying "There's only one (known) kind of heat in the universe. It's either a heat engine or it is something totally different. There is no conventional and unconventional heat."
     
  20. Jan 22, 2009 #19
    I can't see the analogy. Also that example is incomprehensible and silly. No need to be offended. I was just stating a fact. Let's try to stick in the topic.
     
  21. Jan 22, 2009 #20

    Monique

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    I've heard of conditions where a physician will cut a nerve that is causing a noxious stimulus, but this is not an easy thing to do. What exactly is your idea about the application of the concept?
     
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