muscle relaxation

Active, thus why rigor mortis sets in after death.

 

I actually got this question in a MCQ paper once.
It is an active process, but to cause relaxation you also need atp.
Basically, ATP is needed both for contraction and relaxation, but when no atp is available, the muslces just 'stick' in the 'on' position.

It's like in your car, you need to put it into drive from park. Both require movement of the stick. But you still need to move the stick into park, it can't happen for itself. err

I think i just confused myself

 

You are, however, correct to say that it does not cost an ATP to relax the muscle. To relax, you merely need to bind a new ATP. That ATP is not used until the next contraction. So, it does require ATP but to say that it is an energy requiring process might not be exactly accurate.

 

Don't you need ATP for the atpase activity to allow reaccumulation of the caclium in the sarcoplasm.

 

Yes, but that isn't what actually drives the process of relaxation, although it is necessary to maintain relaxation.

 

oh ok

 

My anatomy textbook actually lists the reuptake of calcium into the sarcoplasmic reticulum (by an active pump) as the very first step of relaxation. without calcium in the sarcoplasm the tropomyosin-troponin complex changes shape and covers myosin binding sites which= relaxation. So yes relaxation is an active process.

 

Your'e referring to an individual myosin head when you say that as it binds ATP it relaxes, which is true. But there are many other myosin heads contracting asynchronously so as a WHOLE, the muscle fiber does not relax upon the binding of ATP, instead it relaxes upon the uptake of calcium into the S.R.

 

NO NO NO!!!

all you need for relaxation is Skelaxin...or so the patients keep telling (demanding from) me.

 

Yes, but (at least in the heart) there are also sodium-calcium antiporters in the sarcolemma. They allow calcium to leave the cell, fueled by the external sodium gradient. It's the the balance between these antiporters and the SR Ca++ ATPase that is important. I suppose you could argue that the sodium gradient to fuel the sodium-calcium antiporter wouldn't exist without ATP, since ATP is needed to maintain the Na+/K+ pump. I guess that's why it's called secondary active transport. I'd say that muscle relaxation is an active process in the grand scheme of things, but not when you hone in on an individual myosin head dissociating from the myosin-binding site (and by active, I mean that ATP is hydrolyzed).

 

Skelaxin aka metaxalone

more info below:

http://www.medicinenet.com/metaxalone-oral/article.htm

 

http://healthmad.com/health/mnemonics-for-remembering-skeletal-muscle-relaxants/

 

you do realize you just necrobumped a 10 year old thread?

 

Yup m sorry