Sliding Filament Model

[vertciel]

Hello everyone:

In my 7th edition Campbell and Reece Biology textbook, a diagram depicts the sliding filament model as a process in which the myosin head cuases the thin filament (Actin) to move toward the centre of sarcomere (i.e. a one-way process).

However, I am wondering how the actin would revert to its normal position after contracting.

Thanks!

[mith]

the atp is removed after each contraction

[vertciel]

Thanks for your reply, mith.

However, how does the actin revert after the removal of the ATP?

Does it revert normally (like a released spring) or must myosin heads pull it back?

[ivan]

The resulting decrease in calcium concentration causes the thin filament to slide back past the thick filament and the muscle to relax.

hehe..that will be our lesson tomorrow. hope, it'll help.

[Darby]

To a large extent, a contracted skeletal muscle doesn't revert until it's pulled out by the antagonist, so you could say that the filaments are physically pulled back into place once they are no longer bound.