How can a rowing boat explain muscle contraction?
If you've never been able to understand 𝐡𝐨𝐰 muscle contraction actually occurs, thinking of a rowing boat will definitely help you out. ⁣

Why? Because the rowing boat follows very similar mechanics! ⁣

💡First of all, let's see how muscle contraction works. There are several steps to go through, and for the sake of making it easily accessible to everyone, i'll try to make is as short as possible!

Anyway, as I said, muscle contractions goes through several steps, yet this number of actions happens within milliseconds!

1) Calcium is released by the terminal cisternae in the Sarcoplasmic Reticulum, which binds to the Troponin, causing a "conformational change" and allowing the Actin binding-sites to be exposed. ⁣

2) Normally, Myosin heads carry ATP which keeps them detached from Actin, however as ATP is hydrolyzed in ADP and inorganic phosphate, Myosin heads bind to the binding site of Actin. ⁣

3) ADP and inorganic phosphate are then released from the Myosin heads, causing "the power stroke", which is basically 𝘵𝘩𝘦 𝘧𝘭𝘦𝘹𝘪𝘰𝘯 𝘰𝘧 𝘵𝘩𝘦 𝘔𝘺𝘰𝘴𝘪𝘯 𝘩𝘦𝘢𝘥 𝘵𝘰𝘸𝘢𝘳𝘥𝘴 𝘵𝘩𝘦 𝘰𝘱𝘱𝘰𝘴𝘪𝘯𝘨 𝘥𝘪𝘳𝘦𝘤𝘵𝘪𝘰𝘯, causing the Actin to slide across. ⁣

4) ATP binds to the Myosin head again and causes the' heads' to detach from the Actin. ⁣

This ATP is then re-hydrolyzed in ADP and inorganic phosphate and causes the head to bind to the Actin and so on. As the Myosin Head "pulls" the actin for a short distance, it needs to be "re-cocked" in order to repeat the process. This of course, requires more ATP!

The whole mechanics of this process resample a rowing boat, which is how you can think about Myosin heads binding on Actin creating cross-bridges. ⁣