Another "Itching" Thread

[antimatter]

All these threads in Anatomy, Physiology and Neuroscience about itching have gotten me curious.

When a stimulus causes an itch, what will happen if we never respond to it?

Aside from the intense frustration and annoyance of having a perpetual itch.

Will it cause any after-effects if you don't itch?

 

Sorry if this is a stupid question, I just started thinking about it when I was getting my hair cut and some hair landed on my nose, and it started itching.

[ecoli]

depends what's causing the itch... if it's a caustic material, your body is telling you to remove, than perhaps.

[antimatter]

Right, but that's basically the workings of the material that's causing the itch.

My question more relates to the neuroscience point of view;

will there be any damage nerve-wise from not responding to an itch?

 

I was thinking that maybe it's one of those things, that when you ignore it long enough it stops working...but this is all guessing.

Can anyone shed some light on this?

[iNow]

If you ignored it long enough, wouldn't you just become desensitized? I don't really think it would matter whether or not the stimulus remained constant if you ignored it and/or adapted to it.

[antimatter]

So would that mean you would never have that itching sensation again?

[Taq_is_hot]

If you ignored it long enough, wouldn't you just become desensitized? I don't really think it would matter whether or not the stimulus remained constant if you ignored it and/or adapted to it.

 

I would think you would get adapted to it after a while. Except when you have an allergic reaction like a rash or something. Then you'd have to get rid of the rash to get rid of the itch. Dang! Reading this is making me itchy!

[Realitycheck]

With nerve damage, it's possible to feel an itching sensation and have no valid stimulus.

[antimatter]

Right, but that's not really what this thread is about...

 

Would there be permanent nerve damage from IGNORING a stimulus, and sure agentchange,

maybe even an imaginary stimulus.

[iNow]

I suppose there is a risk of a nerve cell being "over-fired" and then crippling itself, but each time it fires new dendritic connections would form and the neural web in that pathway would become denser... likely to cancel the effects of a small handful of individual cells exhausting.

 

I'm not 100% sure on the above, but I think it's reasonable.

[antimatter]

How would the new connections form if it was crippled?

[iNow]

Let me ask you first... Do you understand how new connections are formed when the cell is perfectly healthy? If not, I'd start there.

[antimatter]

Not really

Would you giving me a basic explanation? If not that's alright, I might be able to find a website with some information on it.

[iNow]

Not really

Would you giving me a basic explanation? If not that's alright, I might be able to find a website with some information on it.

 

Brilliant answer, and a good indication of your character.

 

Start here, click links when you need clarification, then come back here once you've refined your questions. I won't necessarily be able to answer it, but we might be able to figure it out together.

 

http://en.wikipedia.org/wiki/Dendrite

[antimatter]

heh

I can't tell if you're being sarcastic in the first line, but oh well...

 

Okay, so I see what you were saying now, I guess it all makes slightly more sense, thanks for the links.

[iNow]

heh

I can't tell if you're being sarcastic in the first line, but oh well...

 

No! Not at all, antimatter. Your response was perfect. You said basically that you did not know, but you wanted to learn. You requested help, but also stated that you would put some effort in on your own. I really meant what I said, and your response is a sign of good character. No sarcasm intended.

[antimatter]

Thanks, I think that's one of the first times someone's been nice to me here!

 

But uh...I have one question, can there be a sort of..surplus of nerves?

Like if too many dendrite connections are formed

[iNow]

Not that I know of. As far as I'm aware, the more connections, the better the response. When the connections are not used, they get trimmed, or "pruned."

[antimatter]

Does that just happen automatically?

Or do the dendrites just sort of die like flowers?

Sorry if these are stupid questions, I'm not really to confident of my knowledge of the nervous system yet.

[iNow]

Well, there is a natural process where some connections are strengthened and others are cut, and it's very active. The body is doing this all of the time. The simplest analogy is to think of larger muscles (this doesn't apply completely, but it gets the same idea across... just remember that analogies are inherently limited).

 

If you taped your left arm to your body for a year, taped in such a way that you could not use it or wiggle your fingers, your left arm would become very weak, it would emaciate, and it would slowly die. Your right arm, being dominant, would get stronger and more robust. Similar with nerve cells.

 

It's a "use it or lose it" phenomenon. Those that are used most become strongest. Those that are used least are essentially discarded, forever making the neural web more dense and efficient.

 

Another analogy I always liked was one of erosion. You have a hillside covered in dirt. When it rains on that hillside for the first time, the rain trickles down the hill in various ways, not following any single path, but going all over the place. However, the next time it rains, there are some "divets" or "indentations" in the dirt hill from the last time it rained. So, the water from this second rain will start to move toward those channels, making them deeper and wider. As it continues to rain, the channels finally become the primary pathway for rainwater to flow down the hill, and nearly all of the rain will move toward them... making the "eroded" channel the primary conduit. Same with nerves. The more the path is used, the more connections are formed. The less the path is used, the more connections are severed.

 

I apologize, it's been more than a decade since my last course in this material, so I'm going to have to rely somewhat on links to help me out. The "method" of how these connections are pruned and grown is basically chemistry. Actin comes out of the cells when forming new connections and things like synaptotrophin trim them:

 

http://ucsdnews.ucsd.edu/newsrel/science/mccell.htm

In their experiments, the UCSD researchers discovered that when they stimulated a cell once, the actin inside the cell was activated and temporarily moved toward neurons to which they were connected. The activity in the first cell also stimulated the movement of actin in neighboring neurons, which moved away from the activated cell. Those changes in the cells were temporary, however, lasting for about three to five minutes and disappearing within five to 10 minutes.

 

"The short-term changes are just part of the normal way the nerve cells talk to each other," says Colicos. "The long-term changes in the neurons occur only after the neurons are stimulated four times over the course of an hour. The synapse will actually split and new synapses will form, producing a permanent change that will presumably last for the rest of your life."

 

 

http://www.sciencedaily.com/releases/2005/11/051126141322.htm

"Our findings are a significant step in our goal of understanding how the brain maintains its synaptic integrity," Morgan said. "Moreover, these findings open the possibility that disruption of synaptotrophin function could play a role in the development of neurological and psychiatric disorders. Therefore, these proteins and the pathways through which they function might represent potential targets for therapeutic intervention in neurological and psychiatric diseases."

 

Like I said, my knowledge is pretty rusty. The idea we are discussing I think would be best googled as neuroplasticity.

 

 

There's no such thing as stupid questions, just sometimes stupid people asking and answering them.

[antimatter]

Okay, that makes a lot of sense now, thanks.

[antimatter]

Oh, one more question:

Is there some disease that makes it so that your connections aren't 'cut'?

So everything has an over-amount of these connections?

 

It's still a little difficult for me to grasp the concept, sorry if what I'm saying doesn't make any sense.

[iNow]

Hmmm.... I'm not too sure. If you have some time to sit through a lecture, this one is quite good. The first one starts about 2 minutes in:

 

 

"There Are No Ghosts in Your Brain: Materialist Explanations for the Mind and Religious Belief"

 

http://video.google.co.uk/videoplay?docid=-8809660521227813170

 

http://video.google.co.uk/videoplay?docid=1800447793352878072

[antimatter]

Thanks for the links, I started listening to the first one, which was very interesting, but unfortunately I don't have time right now (Essays...lots), when I listen to them I'll reply back on this thread.

[iNow]

Please do. It's about an hour and a half in total, so grab some popcorn and a tasty beverage before you start.