brew - 21-6-2008 at 21:05
A quick question regarding the effect of a build up of potasium ions when smooth muscle is being continously stimulated before fatigue sets in.
Resting membrane potential is around -70mV and depolarising effect of Action potential is causing the efflux of pottasium ions in the ECF. Obviously
this can go into the aspect of the effect that this may have on the Na+K+atpase pump or leak channels that maintains resting potential but I think I
need a simple overal quick effect that does not go into rates of transport etc. I am exhausted and perhaps being lazy but thought I would put the
question in case someone has looked at this and can give me a hint. I think the amplitude of the peak will be reduced as less K+ ions will be needed
to reach +30mV due to the fact that the ECF is more positive than normal. I cant get my head into gear with this. I have googled it and found various
papers on this but it goes into specific effects regarding K+ blockage and rate variant etc. Its probably very simple so much so that I am missing it.
Any help would be appreciated.
brew - 22-6-2008 at 00:01
I think I have nuted it out. I think it is purely a stimulating effect. Resting membrane potentail becomes closer to threshold and action potentials
can occur more easily. This may result in an increased rate of fatigue if my thinking is correct.
brew - 22-6-2008 at 03:15
Spoke to lecturer, my thinking was somewhat right. Smooth muscle is extremely resistant to fatigue but would of been greatly stimulated and eventualy
the excess K+ would diffuse into the cell thus totaly messing up the electrolyte balance thus no responce to electrical signal fullstop. This would
not stop the constant level of tone for the muscle as this is due to a constant supply of Ca+ and is not fully depandant on electrical stimulation.
I know I am somewhat talking to my self here but considering I started this dialogue, I thought I should see it through. All right. I talkto myself
and even do so in forums. Totaly fucking mad
solo - 22-6-2008 at 08:05
Think about it, example leg muscle is a type of smooth muscle, what happens when a person on diuretics fails to supplement potassium in their
diet....leg cramps, hence the lack of potassium causes an electrolyte inbalance....which is corrected by a potassium supplement or fruits high in
potassium i.e. bananas........solo
brew - 22-6-2008 at 13:31
This situation was when a piece of rabbit small intestine kept alive by being bathed in a specific solutin(ringers or tyrodes I cant remember)and was
hooked up to a power source and force transducer I think etc, and the force of contraction could be determined. It was a range of experiments using
various neurotransmitters, bathing solutions, types of stimulation - various frequencies etc, and I had been unwell and had to leave. What you have
implied is that the diuretic therefore increased urination could lead to a reduction of K+ ions be it skeletal muscle(leg) or smooth muscle -single
unit (predominately in the GI tract) and thus leading to an electrolyte inbalance that results in cramp. I did understand that in my case it was an
increase in K+ that would also lead to an inbalance but was unsure of the effect. I assumed it would overtly stimulate the muscle which was the case
but it would not result in fatigue which I thought. What you have stated makes scence and I appreciate your input. Sometimes when I have to answer
questions I delve too deeply and miss what is staring me in the face.
bmc