Pain in the peripheral nervous system

In summary, the peripheral nervous system sends messages of pain to the brain through electrical impulses, which can vary in intensity depending on the stimulus. The nociceptor is responsible for sensing injury and causing pain, while other receptors respond to different types of information. The actual signal that travels to the brain includes a threshold, action potential, and refractory period. Pain is a subjective experience and can also be caused by psychological factors. Some conditions, such as simple partial seizures, can manifest as pain without any apparent physical cause. The definition of pain should not be tied to the stimulus, but rather to the individual's subjective experience.
  • #1
misgfool
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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  • #2
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): http://linkinghub.elsevier.com/retrieve/pii/S0959-4388(97)80028-1" .
 
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  • #3
Monique said:
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.

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:

Monique said:
The introduction of this review is interesting (about the difference between non-painful and painful sensory stimuli): http://linkinghub.elsevier.com/retrieve/pii/S0959-4388(97)80028-1" .

I was looking for a bit (100%) cheaper article.
 
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  • #4
misgfool said:
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:
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.
 
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  • #5
misgfool said:
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.
Wikipedia is free:

The conduction of nerve impulses is an example of an all-or-none response. In other words, if a neuron responds at all, then it must respond completely. The greater the intensity of stimulation does not produce a stronger signal but can produce more impulses per second. There are different types of receptor response to stimulus, slowly adapting or tonic receptors respond to steady stimulus and produce a steady rate of firing. These tonic receptors most often respond to increased intensity of stimulus by increasing their firing frequency, usually as a power function of stimulus plotted against impulses per second. This can be likened to an intrinsic property of light where to get greater intensity of a specific frequency (color) there has to be more photons, as the photons can't become "stronger" for a specific frequency.

http://en.wikipedia.org/wiki/Neuron
 
  • #6
Nociception isn't pain. Nociception is the message that is sent to brain.
http://www.iasp-pain.org/AM/Template.cfm?Section=General_Resource_Links&Template=/CM/HTMLDisplay.cfm&ContentID=3058#Pain" is created only by brain.

Pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. Note: The inability to communicate verbally does not negate the possibility that an individual is experiencing pain and is in need of appropriate pain-relieving treatment. Pain is always subjective. Each individual learns the application of the word through experiences related to injury in early life. Biologists recognize that those stimuli which cause pain are liable to damage tissue. Accordingly, pain is that experience we associate with actual or potential tissue damage. It is unquestionably a sensation in a part or parts of the body, but it is also always unpleasant and therefore also an emotional experience. Experiences which resemble pain but are not unpleasant, e.g., pricking, should not be called pain. Unpleasant abnormal experiences (dysesthesias) may also be pain but are not necessarily so because, subjectively, they may not have the usual sensory qualities of pain.

Many people report pain in the absence of tissue damage or any likely pathophysiological cause; usually this happens for psychological reasons. There is usually no way to distinguish their experience from that due to tissue damage if we take the subjective report. If they regard their experience as pain and if they report it in the same ways as pain caused by tissue damage, it should be accepted as pain. This definition avoids tying pain to the stimulus. Activity induced in the nociceptor and nociceptive pathways by a noxious stimulus is not pain, which is always a psychological state, even though we may well appreciate that pain most often has a proximate physical cause.
 
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  • #7
Many people report pain in the absence of tissue damage or any likely pathophysiological cause; usually this happens for psychological reasons.

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:

# Symptoms associated with seizures from the postcentral gyrus include tingling, numbness, pain, heat, cold, agnosia, phantom sensations, or sensations of movement.
# Abdominal pain usually originates from the temporal lobe, and genital pain from the mesial parietal sensory cortex.

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/3137487From Somasimple's quote:
There is usually no way to distinguish their experience from that due to tissue damage if we take the subjective report. If they regard their experience as pain and if they report it in the same ways as pain caused by tissue damage, it should be accepted as pain. This definition avoids tying pain to the stimulus. Activity induced in the nociceptor and nociceptive pathways by a noxious stimulus is not pain, which is always a psychological state, even though we may well appreciate that pain most often has a proximate physical cause.

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.
 
  • #8
Monique said:
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.

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?
 
  • #9
misgfool said:
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?
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.
 
  • #10
zoobyshoe said:
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.

I know a lot (almost all) about electric circuits, but very little of axons.
 
  • #11
misgfool said:
Ok, so the voltage (amplitude) of the signal is higher for extreme pain than for slight pain.
No, it is the number of pulses that are generated by the neuron.
 
  • #12
somasimple said:
Nociception isn't pain. Nociception is the message that is sent to brain.

Pain is created only by brain.
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.
 
  • #13
turbo-1 said:
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.

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.
 
  • #14
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.
 
  • #15
somasimple said:
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.

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.
 
  • #16
misgfool said:
If nerves have electric consequences, they can be integrated with electric circuits.
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.
 
  • #17
zoobyshoe said:
The point is that you can't simply splice any old conductor into an axon.

How about a new one? :smile: My purpose is not to make an axon, only something that can interface with axons.

zoobyshoe said:
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.

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.

Wikipedia said:
It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart.

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
 
  • #18
misgfool said:
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.
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."
 
  • #19
zoobyshoe said:
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."

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.
 
  • #20
misgfool said:
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.
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?
 
  • #21
misgfool said:
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.
It's sounding more like you want to be a pain in the peripheral nervous system rather than alleviating it.:biggrin:
 
  • #22
Monique said:
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?

I'm fairly good in what I choose to do. Really, I am. But I came up with this idea about 6 hours ago in a bus (while watching a charming young lady who had green eyes by the way), so you are demanding quite a lot at this point of the (hobby) project. I'm good, but not quite that good. However, while technical issues are very easy to solve, the biological side is still bit of a question mark. And that's where I could use some help.

zoobyshoe said:
It's sounding more like you want to be a pain in the peripheral nervous system rather than alleviating it.

All the more reason for you to focus in developing this chip, so that you can program it to filter the pain I'm causing. :smile:
 
  • #23
misgfool said:
All the more reason for you to focus in developing this chip, so that you can program it to filter the pain I'm causing. :smile:
How do you dial back pain safely? If your hardware solution makes extreme pain tolerable, how is the implantee going to be able to distinguish between pain that indicates that a mild amount of tissue damage may be occurring, and a (damped) sensation that on examination reveals that some really extreme damage is occurring? Doctors already have tools at their disposal (including narcotics) to deal with chronic pain, though as I posted above, their tools to deal with neuropathic-induced pain are limited and sufferers pretty much have to learn to live with it.

Pain is not pleasant, but it has real survival value.
 
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  • #24
Monique said:
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?
And they stopped because they can't cut the brain.
 
  • #25
Pain is part of a security system. Without pain no life. Patient who do not feel pain have a short life time (<20 yrears).
 
  • #26
zoobyshoe said:
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.
See Ramachanfran and phantom limb pain.
http://en.wikipedia.org/wiki/Phantom_limb
Psychology is the result of neurons activation: a physical process.
 
  • #27
misgfool said:
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.
A ion that is moving creates an electric field that is effectively electricity but where is the circuit?
Conventional electronic chips need electric circuits. A neuron has no dedicated wires or electric circuit. No circuit let's an useless electric field.
And a chip needs energy.
 
  • #28
And a last and quite definite problem is that you can't cut an axon without killing it.
 
  • #29
somasimple said:
And they stopped because they can't cut the brain.
What's this problem you have with the brain? If a neuron is misfiring and thus causing trouble, you need to tame it. The brain adds another level of complexity and it certainly can cause problems, but that does not mean you can completely ignore the effect of the neuron itself.
 
  • #30
Where do go neurons? Where are they connected?
I have no problem with brain. Brain is the masterpiece of pain. Without brain no pain.
 
  • #31
turbo-1 said:
Pain is not pleasant, but it has real survival value.

Yes, but if it is chronic and severe, it doesn't really help. I would also like to reduce the medical payload people get, since drugs often have undesirable side effects. Unfortunately, the chip wouldn't help you.
 
  • #32
somasimple said:
A ion that is moving creates an electric field that is effectively electricity but where is the circuit?
Conventional electronic chips need electric circuits. A neuron has no dedicated wires or electric circuit. No circuit let's an useless electric field.

I already solved this problem. I'm not going to go into details.

somasimple said:
And a chip needs energy.

Yes.

somasimple said:
And a last and quite definite problem is that you can't cut an axon without killing it.

I wouldn't cut an axon, just separate two of them from each others.
 
  • #33
I wouldn't cut an axon, just separate two of them from each others.
it doesn't mean anything, sorry.
An axon is a single piece you can't separate from the soma.
 
  • #34
somasimple said:
it doesn't mean anything, sorry.
An axon is a single piece you can't separate from the soma.

Ok, thanks all for help.
 
  • #35
A nerve is a bundle that contains thousands and thousand axons. Of course, they aren't labeled so you do not know which are transmitting nociception.
http://en.wikipedia.org/wiki/Neuron
 

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