sliding filamen

[victor]

Someone please explain about muscle sliding filamen theory in a simple way...I have a difficulities in understanding that topic in my textbook.

[ewokgod]

the process is as following:

1. In ACTIN thin filament, Ca++ stimulates troponin to pull tropomyosin away from the myosin binding site (tropomyosin normaly 'covers' the binding site with myosin in relaxed muscle state).
Tropomyosin molecules lie in the groove between 2 actin chains. Troponin lies at the intervals along tropomyosin molecule.

2. Having the site exposed, actin can bind with myosin. Having adequate ATP, contraction can occur.
Contraction process:
- myosin crossbridge binds with actin sub unit at the binding site.
- if ATP is present, myosin binds to ATP and actin is released.
- ATP is then hydrolised to ADP, the energy released recocks the myosin crossbridge.
- recocked myosin crossbridge binds with the next actin sub unit, by moving through a short arc (the "power stroke"), pulling the actin filament.

3. When the contraction is completed, Ca++ is pumped back to sarcoplasmic reticulum and tropomyosin covers the actin-myosin binding site. Muscle relaxes.

Thats as simple as i can make them. Hopefully it helps.

[victor]

Wow..this is really helpful. I'll print it out and start to read them..thanks a lot.

[didgi]

are the actin and myosin filiments locked in place during a muscle cramp, if they are is it because there is no ATP and if thats not true, what is causing the muscle to cramp? Thankyou