Mechanism of Sliding Filament Model

Question 1

What is the stage of stimulation

Answer 1

Everything relaxed rn - once action potential arrives, it depolarises the Sacrolemma and the sacroplasmic reticulum. This will open the voltage gated calcium ion channels on the SR to open to release calcium ions into sacroplasm. This Ca2+ then binds to troponin which causes a conformational change - exposing the actin-myosin binding sites

Question 2

What is the stage of attachment

Answer 2

Cos the actin binding sites are revealed - myosin heads can bind, forming cross bridges. The myosin filament will then flex, pulling along the actin. This also then releases the ADP

Question 3

What is the stage of detachment

Answer 3

Now ADP released - ATP can bind to it which releases the head from the binding site. However the myosin head needs to reach its normal position so it can keep pushing the actin filament along. A calcium ion comes along and binds to the myosin head, activating the ATPase component in the head, hydrolysing the ATP back into ADP, this will give energy to move the head back to normal, allowing it to bind to the next site