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I get a lot of PM's about physiology: why things work the way they do in the body. I would like to have a place where people can ask that kind of question and I'll do my best to answer so everyone can read the answer. I will reduce the repeat answers in pm for me

Here is one I got recently:

reading over the threads on vasodilation again I'm getting confused about something very basic: why is vasodilation good? If it affects mostly the arteries one would imagine pressure building up toward the veins, or not?

Also, do you remember whether Niacin flush has ever been brought up?

That is a good question . The issue regarding any vasodilators is that they impact the arteries a lot more than the veins. Arteries have smooth muscles are strong thick vessels where veins are thin and passive. Arteries have to withstand the pulse, veins barely feel it at all because they are on the other side of the capillary bed. Vasoconstriction though is bad for the CCSVI paradigm as it would restrict blood flow a little more and we are already looking at hypoxic circumstances, therefore the idea of dilators ends up being preferable.

Niacin is a potent temporary vasodilator (as long as you get the regular kind not the no flush kind) and we have discussed it with the same speculative "vigor"

The amyl nitrite research in which persons in relapse had a dramatic turn around in function makes you wonder if it might not help a person in relapse a little bit .

as for veins getting too much blood after the arteries open up, that is a speculation with regards to stenosis. In general with vasodilation the blood pressure drops....so more blood but less pressure. a flushing effect for the veins.

Marie -- I have a question:

Somewhere or other I got the idea that blood vessels (both arteries and veins) had smooth muscles in their walls. Then, according to a post by Cheerleader one of the speakers in Bologna, Dr. Guilio Gabbiani from the Centre Medical Universitaire in Geneve, Switzerland, compared arteries and veins: arteries are thicker and there is more resistance; veins have smooth muscles, arteries never contain smooth muscle cells. (This information contradicted my understanding of smooth muscles and blood vessels.)

Now you have written:

Arteries have smooth muscles are strong thick vessels where veins are thin and passive.

Where can I find a definitive source to clear my confusion? Which blood vessels have smooth muscles?

Dr. Guilio Gabbiani from the Centre Medical Universitaire in Geneve, Switzerland
speaking on jugular wall changes in MS. His laboratory was interested in the fibrotic changes. He was interested in learning the importance of venous morphology, and is surprised so little is known.

Comparing arteries to veins:
Arteries are thicker and there is more resistance.
Veins contain smooth muscle cells, and arteries never contain smooth muscle cells.

this is what was said...what I wrote down regarding SMCs....
coulda been operator error
cheer

Anatomy of the arterial wall here
http://en.wikipedia.org/wiki/Artery note smooth muscle on the picture

Explanation of the blood vessels here
http://www.fi.edu/learn/heart/vessels/veins.html

You are right they both do but the wall is very thin in veins and it is relatively weak. The vaso dilation and vaso constriction impact the veins a lot less.

Marie - your thread is a great idea! Thank you again for sharing your knowledge and your expertise. And, may I add --- you write it so that us lay people can understand.

You are the best!
Sharon

Just wanted to clarify what Dr. Gabbiani was talking about in terms of smooth muscle cells- He compared tissue samples of the jugular vein walls from Dr. Zamboni's patients to control autopsy tissue. He mentioned that in MS patients, the internal jugular veins walls had many more smooth muscle cells than the controls.

He also saw that there was less collagen I type fibers in the MS jugular vein tissue than controls, and more collagen III fibers in MS. This was the exact opposite of the controls. Collagen III is stiffer and fibrosis takes place. This was the main point of his presentation-
hope that clears up the smooth muscle cell mention in my Bologna notes-

thanks for clearing stuff up for us, Marie. We're really lucky to have you on here!
cheer

Thanks! I got some great questions in PM and decided that maybe others would like to discuss the same things. There are some fabulous minds here on TIMS and they ask questions that show deep thinking and questioning.

Please others feel free to answer too I just thought maybe we needed a place for these kinds of questions to have a home. I have no desire to be the only answering person here. Maybe we should offer references if we answer on this thread?? I think I should stick to that too....

Thanks, folks.

I got another interesting question in pm that boils down to:

Why are some people heat sensitive and some not?

Speculatively there are probably 2 different mechanisms in play.

1. The venous drainage and the fact the brain is cooled by the veins, and it appears in CCSVI that the venous drainage is slow, thus heat is not removed from the brain as it should be....and

2. The fact that demyelinated and damaged nerves function more poorly in heat. In fact all nerves transmit more sluggishly in heat my neuro told me, so the MSer with her demyelinated nerves has it that much harder.

For the person newly diagnosed early in the disease, you may not notice much heat sensitivity.

Others may notice it quite a bit if their venous stenosis is severe as the emissary veins cool the brain through the venous system, and a plugged venous system may result in a very hot brain in the heat. Such a person may recover hugely when circulation is restored and overnight may be vastly better.

For the person very progressed like me, probably a lot of the heat sensitivity is related to the fact that there is extensive nerve damage. Such a person may recover good venous flow but still feel weaker in the heat due to the simple fact their nerves transmit signals more poorly.

these are my best guesses based on what I understand of the physiology.

Good idea, what does OT mean?

Oh!! Off topic? Like my idea was if someone in a thread suddenly needed to know something that was not related to the thread they could ask it here....

Marie, Another great idea for a topic, thank you.
My question relates to the flip side of the coin -- why are some people so sensitive to cold? Heat doesn't bother me, but as soon as September comes and the air changes, I'm wearing thermals until May so I don't stiffen up and can still move. Any ideas on how that fits in?

.

Needled wrote:why are some people so sensitive to cold? Heat doesn't bother me, but as soon as September comes and the air changes, I'm wearing thermals until May so I don't stiffen up and can still move.

Same with me. Stress does the same exact thing to me as cold. If I get too cold, or if I watch a scary movie, bam: my leg gets stiff and won't work right. Weird.

Hi Needled I do not know the answer to that. I do know that we shiver at several degrees cooler than normal people, so I wonder if the cold temperature "accidentally" triggers a spasm in an attempt to shiver? Spasms are caused by an imbalance of signals in the spine and CNS so that is pure speculation I don't know.
ref: http://www.webmd.com/multiple-sclerosis ... cle-spasms

I too am more spastic and stiff in the cold. Severely. I had that symptoms years before heat sensitivity. For a long time I wondered if I even had MS I tolerated heat fine....

maybe someone else has had a good answer on that from somewhere?