Nociceptive musings 2, 3, 4
Nociceptive musings 6
"Hi there - it's me, C again..
"I found another picture to sum up what I do. You've heard of people who are shocked by a loud sound, sight or sudden touch, and nearly "jump out of their skin"or "wet their pants"? Same thing happens to me! I'm kind of trapped, so I can't "move" physically, but I can certainly move chemically!
"This picture shows what happens if someone comes along and gives me a high-enough-threshold surprise that I "jump."
|When a nociceptor fires|
"Keratinocytes are skin cells (step-siblings of mine, the offspring of BlueDad, from the last post). When I fire an action potential the stuff that squirts out stimulates them to grow.
"Think how cleverly this worked out for evolution - if I'm getting prodded hard enough to make me jump, chances are pretty high some skin damage may have happened, and what a lucky thing for skin cells - the stuff I produce helps them divide and grow, so the potential "wound" can heal quicker! Win-win for them!
"Another side though - have you ever had a rash? If it had nothing to do with being in contact with poison ivy or some other irritant, chances are that was a fight going on in your skin, that was straight from your nervous system. By that, I mean, maybe it was a "neurogenic" rash. Hey, I can be affected at either end, so if there was a lot of stress going on, Upstairs, it could have been felt by me... if there was enough of it going on that I become sensitized, I leaked easier, which bothered the skin cells and immune cells faster than my products could be carted away by the lymph system. The skin cells grew, were inflamed, because the immune cells thought they had to fight something, the skin layer swelled because I bothered the arterioles and venules... it all occurred just as if there had been some kind of "danger", some kind of skin breach, except, there wasn't! It was just me, being over-stimulated, growing too many receptors, making more stuff than normal, becoming too easily bothered and leaky... bothering myself in the process.
"Hey, I don't like when that happens any more than a baby likes to sit in its own wet diaper feeling the burn from its own diaper rash. All of us feel it!"
"Mast cells make their own kind of horribleness when they are stimulated by me, which affects me and everyone else in their own particular ways, just to add more biochemical complexity to the situation. I mean, I'm sensitive to histamine, serotonin, prostaglandins, nitric oxide.. don't get me started on all the kinds of leukocytes - eyew! Cytokines, prostanoids, leukotrienes, and more nitric oxide.. and only just a few things in the kind of inflammatory soup we can all end up in, me and my Delicious's, if we start over stimulating each other."
"Smooth muscle cells are everywhere, all through skin, hypodermis, walls of vessels, walls of glands, ducts, viscera, erector muscles for hair shafts, goose bumps, you name it. Everywhere striated muscle isn't, I guess you could say. The stuff I make stimulates it to contract. It needs me to stimulate it to contract! Well, me and the autonomic system, depending where and what for..
"Bodies need smooth muscle, and it's nice to feel needed, but what's not so good, is if contraction of smooth muscle becomes chronically overstimulated, happens to squeeze down too hard on something that's important, i.e., me, or some other kind of neural structure. Or vascular structure. Or drainage structure. That can mess big time with physiology as usual."
"Like we already saw, nothing happens at the capillary level except capillary action. They don't respond to anything, because they don't have to. But the vessels just ahead of them get bigger, and the ones behind them leak.
"If the vessels ahead of them get bigger, more capillaries open up (lazy things! - there are usually more of them available than actually function, kind of like those so-called "work crews," where 10 guys stand around and watch while one guy does all the shovelling) to handle the increased flow. Venules "extravasate" - that means, they leak. What do they leak? Plasma. What's in the plasma? Bradykinin and serotonin! So, yay [not]! More stuff to irritate me, and other nearby nociceptors that all were just minding their own business, until they activated because of the stuff in the plasma!"
Mason P; Medical Neurobiology Oxford University Press, USA; 1 edition (May 19, 2011)