Calcium and Muscle fibers

[Powel6016]

Hey,

What happens when adequate ATP is present within the muscle fiber, but action potentials occur at a frequency so great that calcium ions are not transported back into the sarcoplasmic reticulum between individual action potentials?


Please help, anything would be helpful. This is for my anatomy class.

Peace,
Justin

[biostudent84]

I think it causes delays in nerve firings. But someone else might know better than I.

Kyle

P.S. No, I'm not being "snooty" by saying "better than I." I've had a number of professors yell at me for saying "better than me."

[ewokgod]

when Ca++ can't be pumped back to sarcoplasmic reticulum, it will ultimately result in malignant hyperthermia.

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.
- when myosin binds with ATP, it releases actin.
- ATP is hydrolised to ADP, the energy recocks the myosin crossbridge.
- recocked myosin crossbridge binds with the next actin sub unit, by moving through a short arc, pulling the actin filament (and ADP is released).

3. the failure to pump Ca++ back to sarcoplasmic reticulum, the binding site in actin is continuously exposed and free to bind with myosin. Therefore, continuous contraction. This goes on until ATP is used up and it as an alternative source of energy, it breaks down glucose anaerobically producing lactic acid.

4. The heat produced increases the temperature uncontrolably (thus the term malignant hyperthermia). This with the lactic acid also screw up your muscle structure.

there you go, hopefully this is helpful.

[mith]

Great answer! So basically the person's muscles just lock up?

@kyle,
it's better than me because it's a direct object.

[ewokgod]

yes pretty much. until they inject dantrolene (muscle relaxant) into the person..