Myosin-based vs. actin-based muscle regulation

[arc5005]

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This isn't due to a particular question, but I made a couple anki cards, referencing:

1) cardiac/smooth muscle is "myosin-based" regulation of muscle contraction.

2) Skeletal muscle is "actin-based" regulation of muscle contraction.

I'm trying to find online how/what this actually means, but I"m struggling to find something that explains the concept at all. I'm wondering if this is even a concept I need to know? need to know for the MCAT?

 

[Spectar]

Yeah so essentially there are two mechanisms of action (contraction) depending on type of muscle.

The first and most important is skeletal muscle. This is essentially the standard muscle contraction image you are probably familiar with. This is where calcium is released from the ER and binds to troponin etc. and myosin interacts with actin and pulls the actin closer together and that is the "contraction." This is very high yield.

For smooth muscle, it has to do with calmodulin (a second messenger) that activates myosin light chain kinase and phosphorylates myosin which undergoes the crossbridge cycle. Here is link better explaining it. This is very low yield, I would just know the main pathway names but I wouldn't be too concerned with it. (deff know that calmodulin is a messenger though).

 

[arc5005]

Yeah so essentially there are two mechanisms of action (contraction) depending on type of muscle.

The first and most important is skeletal muscle. This is essentially the standard muscle contraction image you are probably familiar with. This is where calcium is released from the ER and binds to troponin etc. and myosin interacts with actin and pulls the actin closer together and that is the "contraction." This is very high yield.

For smooth muscle, it has to do with calmodulin (a second messenger) that activates myosin light chain kinase and phosphorylates myosin which undergoes the crossbridge cycle. Here is link better explaining it. This is very low yield, I would just know the main pathway names but I wouldn't be too concerned with it. (deff know that calmodulin is a messenger though).

thank you 🙂