Hey! It’s starting to rain! We should probably go home now.
Yea your probably right, let’s run!
Hey so I was wondering, how does muscle contraction work when we run?
So, There are thick filaments (Myosin) that are anchored on the M line and thin filaments (Actin) anchored on the Z line. A Contraction begins when ATP is hydrolyzed into ADP causing Myosin to extend
Oh wow! Then what?
When an action potential is reached in a striated muscle cell, the sarcoplasmic reticulum releases Calcium ions into the myofibrils. and Calcium binds on Actin.
Actin contains many protein “pearls” linked together. In addition, Actin's two protein fibers Troponin and Tropomyosin connected to it respond to the presence of Ca+2. Troponin binds to Ca+2, which moves Tropomyosin which moves to create binding sites.
And then the myosin head now can attach to Actin at the cross bridge, and triggering a power stroke. The energy stored in the myofilament causes pulling of the filament towards the M line, shortening the Sarcomere and releasing ADP!
yea see you get it!
Lastly, myosin and actin remain attached until ATP attaches once again, breaking the bond at the cross bridge. This frees myosin making it possible for another contraction or to relax.