When I was considering muscle contraction as a whole, this issue came to mind.
Which side should the Z-line of myofibrils shift to when it is being pulled by actin filaments on both sides to which it is attached?
Then, how does muscle contraction actually happen? How does sarcomere decrease in length? ( Because all the adjacent sarcomere needs to be shorten and forces on z line is in opposite directions )
I made numerous searches but came up empty-handed.
