Pain

[Grimbeard]

Originally posted by fafalone

There's a clear distinction between conscious and unconscious rooted thought.

 

I don't mean to be rude, but is there any chance you could explain what you mean by that? I don't seem to be getting your meaning.

[Grimbeard]

Originally posted by fafalone

Your brain does say that, just after the reflex has already been signalled.

 

Exactly - after the reflex - the reflex itself is not indicative of pain

 

<edit> that's why when you stub your toe, for example, you withdraw (reflex) then there's that moment where you know it's about to hurt - pain is a cognitive/emotional response - not a physiological one.

[fafalone]

In this example, you know you've been stick with a pointy object. You know your hand is being pulled away. But your hand starts moving before your brain gets the signal; but it still does get it as you obviously know you were stuck.

[Glider]

The reflex arc is a self-contained functional unit. It has been shown to exist in decortecised animals, cockroaches, sea slugs, flatworms etc.. It is an adaptive hard-wired mechanism for limiting tissue damage on exposure to a potentially harmful stimulus. Fine. We accept that.

 

It's not pain though, nor does it indicate the existence of pain. Can anyone give me a considered, working definition of pain?

[fafalone]

So if you put your hand on a hot coil on your oven and jerk it away, you don't don't feel the heat?

[Glider]

Being a self-contained functional unit, the reflex arc is not dependent upon higher mechanisms. You could, in effect remove the brain and the reflex arc would still function (this has been shown in animal studies). In this case, yes; you would jerk your hand away from a hot coil on your oven, but not feel the heat.

 

To approach it from the 'other end' as it were, if you touch the hot coil and burn your hand, the withdrawal reflex will limit the damage. However, the pain of the burn will persist (possibly for hours). Yet you would not be constantly withdrawing your hand, i.e. the reflex arc would not respond to the persisting nociceptive volleys.

 

This suggests that the reflex arc is not a mediator of pain.

[Sayonara]

Originally posted by Glider

I am in a bar, and I see a nice looking woman. I move next to her and I put a cockroach down her shirt.

Is this something that happens a lot?

 

And you want to know about pain?

 

 

Worrying.

[Glider]

Hey, we all have our hobbies!

 

As for pain, it's what I'm researching. Arguably, to research something effectively, we need to at least be able to define it. There is a definition provided by the International Association for the Study of Pain (IASP), but I was just interested in what normal people thought.

 

D'you think I'm in the wrong place?

[Giles]

It's a sensation, and we can't actually describe it except by mutual experience, as with colour.

 

In physical terms, i assume that as usual there are certain parts of the brain which are involved as part of their general function (both high-level parts and parts dealing with senses directly).

 

Reductionism isn't going to answer the 'where is pain?' question simply. To go any further - well, I can't be expected to solve the mind-body problem here and now, can I?

[fafalone]

The reflex arc isn't dependent on the brain, but the brain does get the signal that the reflex was activated in response to a particular stimulus. Also, once the brain is aware it prevents further reflexes.

[Skye]

At a housewarming I felt something that I thought was a small thorn catching on my calf, I looked down and saw that a dog had bitten me leaving a puncture and some scratches. Then it hurt, like an ache.

 

I guess that our perception of pain is built on our past experiences of it to an extent. I felt the tooth pull back on my skin and my brain equated that to a small thorn. Looking down and seeing a hole, cuts, bruising made my perception change, not only did it hurt more, it hurt differently.

[fafalone]

If that happened to me, once I realized it I would be so pissed off at the dog I wouldn't even feel pain.

[Glider]

Originally posted by Skye

[/b]

At a housewarming I felt something that I thought was a small thorn catching on my calf, I looked down and saw that a dog had bitten me leaving a puncture and some scratches. Then it hurt, like an ache.

 

This could probably be explained by the different receptors involved. Small thinly myelinated fibres (A-delta) mediate sharp, fast pain, whilst very small, non-myelinated © fibres mediate slow, dull aching pain and heat. It's like when you stub your toe, you get the impact (large afferents) and the A-delta mediated sharp, fast shocking pain, but you also have that knowledge that in a second, it's really going to hurt. A split second later, you get that deep aching pain that makes you sweat.

 

I guess that our perception of pain is built on our past experiences of it to an extent. I felt the tooth pull back on my skin and my brain equated that to a small thorn. Looking down and seeing a hole, cuts, bruising made my perception change, not only did it hurt more, it hurt differently.

 

A very good point. Past experience is definitely a factor in the experience of pain. What's most interesting here though, are the changes in your subjective experience (you say it hurt more, and differently) when you looked at the damage. That's very interesting.

[Glider]

Originally posted by fafalone

The reflex arc isn't dependent on the brain, but the brain does get the signal that the reflex was activated in response to a particular stimulus. Also, once the brain is aware it prevents further reflexes.

 

Very true. And yet it still has nothing to do with pain.

[aman]

The human body has set routines it goes through when it is exposed to stimuli. A broken bone will set off the production of endorphins, adrenalin, etc, and also start protective behaviors.

It seems that anything that triggers the same set of reactions in a body could be defined as pain.

Just aman

[Glider]

Originally posted by Giles

It's a sensation, and we can't actually describe it except by mutual experience, as with colour.

 

This is true enough. Unfortunately, it's where a lot of the problem lies, as when assessing pain in another, the clinician can only relate the patient's description to his or her own experience. That seems to leaves room for quite a lot of error doesn't it? This especially becomes an issue when trying to control pain.

 

Imagine you've just had surgery, and I'm part of the pain-control team. I come to you and say "Good morning, how much pain do you have today?" You say "A lot!" and this is what I base your dosage of morphine on?

[fafalone]

Originally posted by Glider

 

Very true. And yet it still has nothing to do with pain.

 

 

So any stimulus that reacts to a reflex arc can't be interpretted as pain by the brain?

[Glider]

Originally posted by aman

The human body has set routines it goes through when it is exposed to stimuli. A broken bone will set off the production of endorphins, adrenalin, etc, and also start protective behaviors.

It seems that anything that triggers the same set of reactions in a body could be defined as pain.

 

Arguably yes. You could say that (as with a broken bone) any trauma which results in a severe inflammatory response (e.g. the release of histamine, prostoglandins and substance P) is pain. The problem here though is twofold.

 

1) The stimulus (trauma) is not pain. Whilst we may reasonable expect trauma to be painful, the trauma itself is not pain per se. Rather, pain (usually) occurs as a result of trauma

 

2) There are exceptions to the rule that trauma results in pain. A good example is the Indian Hook Swinging ceremony which involves a man (the celebrant) having steel hooks inserted under the muscles on each side of his spine. These hooks are attached to ropes, which in turn are attached to a cart. The celebrant is suspended by these hooks and wheeled from village to village where he blesses crops and children. Although he holds the ropes between villages, he swings freely whilst giving the blessings. The trauma of the instertion of these hooks would by western standard be considered agonisingly painful. However, the celbrant shows no sign of discomfort, rather, he seems to be in a state of exultation (see Melzack & Wall, 1982).

 

At the other end of the scale, there are examples of extreme pain occurring in the complete absence of any discernable physical cause. People have even been known to hallucinate pain.

 

So, at two ends of a scale, we can have extreme pain with no physical cause, and an extreme physical 'cause' (trauma which one might reasonably expect to result in pain), in the apparent absence of pain.

 

 

Melzack, R., & Wall, P. (1982). The Challange of Pain. New York: Penguin.

[Glider]

Originally posted by fafalone

So any stimulus that reacts to a reflex arc can't be interpretted as pain by the brain?

 

Stimulus that reacts to a reflex arc?

 

Of stimuli that trigger a withdrawal reflex, some may be interpreted as painful, some may not. The point is the the reflex arc is not the determinent of whether or not such stimuli are percieved as painful.

 

For example, you're out camping and you're sitting around the fire, having a beer and you reach behind you to pick up a new tinny, and your hand contacts something unexpected (say, cold, slimy and moving). That will probably trigger a withdrawal reflex, probably scare the crap out of you too...but it won't be painful. The example you give above, concerning the hot coils on the oven will also trigger a withdrawal reflex, but in this case, the stimulus would probably be perceived as painful. Either way, it has nothing to do with reflex arc. That simply mediates the reflex, not the experience.

[blike]

The trauma of the instertion of these hooks would by western standard be considered agonisingly painful. However, the celbrant shows no sign of discomfort, rather, he seems to be in a state of exultation (see Melzack & Wall, 1982).

 

I don't understand, does he not feel the pain? Or is it because in his culture, that isn't considered pain...

[aman]

Now the definition of pain is moving into the brain and maybe a scan of the area active during actual suffering would show when pain is experienced or overridden.

As far as the reflex arc, it seems to happen in preparation for pain since it is short-cut back to the injury site from the spinal cord while the actual pain information continues on to the brain.

Just aman

[Glider]

Well, this is the problem. Pain is a non-observable phenomenon, we can't measure it like we can blood pressure for example. So, all we have to go on is behaviour and verbal report. People in pain will exhibit 'pain behaviours' (e.g. sheilding, antalgic gait, writhing, moaning etc., etc.), and when asked, will genrally not be shy in telling you if something hurts.

 

In the case of the celebrant described above, he exhibits no pain behaviours, and talks normally to those around him. From these observations, we can only conclude the absence of pain.

 

As for cultural differences, whilst there are differences in the perception of pain that are related to ethnicity and cultural affiliation these differences (whilst statistically significant) are nonetheless very small. Moreover, the evidence suggests that these differences are a result of social learning within cultures, rather than any physiological factors.

 

In short, we have a guy who is not so different from any other guy, yet who appears to suffer no pain whilst suspended by hooks inserted under the muscles lateral to his spine.

 

Pain is a conundrum, innit?

[Glider]

Here's another very good example. Chapman (1984) relates the story of a 9 year-old boy he observed in hospital, just after the boy had undergone a nephrectomy.

 

"As soon as he recovered from the anaesthetic, the boy was transferred to his room. He was given no drugs for postoperative pain in accordance with his surgeon's normal practice.

 

A colleague and I had involved the boy in a transcutaneous electrical stimulation experiment in which electrodes were attached under the bandage and stimulation was initiated before the patient regained consciousness. As the youngster lay in bed with his hands outside the covers, the surgeon and his associates came to visit. The surgeon told him that he could not drink water for the entire day and gave other instructions.

 

Since an experimental intervention was being tried, they repeatedly asked if he felt any pain in his belly. He said, "No, it doesn't hurt", to repeated queries, and everyone was impressed with the apparent success of our intervention.

 

After the surgeon and his retinue had gone, the boy talked more casually with the others in the room. When asked whether there was anything he feared, he began to cry and confessed his terror of the expected operation that would remove his kidney. His surprised nurse tried to reassure him that the surgery had already been done, and that there was nothing to worry about. He refused to believe her. "But don't you remember?" she contended, "That's why they put you to sleep this morning...so they could do the operation". The little boy looked very threatened. "It's not true!" he shouted, "It's not true!" When asked why it couldn't be true, he asserted confidently, "Because I haven't got any bandages". We asked him to feel his belly, since his hands were outside of the bedclothes. When he did, an expression of astonishment came over his face, and he broke into tears, screaming, "It hurts! It hurts!" Thus, the boy's 'analgesia' occurred because no one had told him that he had been operated and not because of our stimulation therapy"

 

 

Something to think about there. It's odd, when you consider that of all things, pain (or more precisely, suffering, as the complete absence of pain would be catastrophic) is probably one of the few experience all humans have in common. Every single individual on the planet (barring those with universal insensitivity) will experience it at some point in their lives, and usually more than once, and with varying degrees of severity. Yet we seem to having a real problem providing a clear and universal definition of it. Interesting, don't you think?

 

Chapman, C. R. (1984). New directions in the understanding and management of pain. Social Science and Medicine, 19 (12), 1261-1277.

[Glider]

Originally posted by aman

Now the definition of pain is moving into the brain and maybe a scan of the area active during actual suffering would show when pain is experienced or overridden.

 

That's a good idea, and that's what was thought a short time ago. Unfortunately it turned out not to be the case. Positron Emission Tomography and functional Magnetic Resonance Imaging has shown that when participants are subjected to a painful stimulus, no single area of the brain 'lights up'. Rather most of it does; the reticular system in the brain-stem, the hypothalamus and thalamus, the medial temporal regions (hippocampus, amydala), the pre-frontal cortex, (including the areas of the anterior cingulate gyrus), the visual cortex, the primary and secondary somatosensory cortices and association areas of the cortex.

 

This would suggest that as with emotion, the experience of pain is a function of circuitry, rather than specific, dedicated 'pain centres'.

[blike]

he broke into tears, screaming, "It hurts! It hurts!" Thus, the boy's 'analgesia' occurred because no one had told him that he had been operated and not because of our stimulation therapy"

 

Very interesting because my brother was ALWAYS the same way as a child. I can remember one specific instance where he fell off his bicycle and gashed open his arm. He got up, picked up his bike and started to ride again. Apparently he didn't realize how bad the wound was. As soon as I told him (and he noticed the blood dripping everywhere) he burst into tears and fell on the ground holding his arm in a protective position.

 

Its kind of like a running joke between him and I; he's never hurt until he sees the wound.