Great job once again on answering the question about how muscle action relates to the movement. I think maybe I took it to the extreme, I went on about agonist, synergist, and antagonist muscles. I wasn't sure if I should add the levers too. It appears as though you explained every type of muscle movement and gave an example of each. I went into flexion at the elbow and discussed that the agonist is the main muscle mover, the antagonist does the opposite, and the synergist is the helper. However, if you think about it, we kind of still came up with the same answer. You discussed flexion and extension and how they are opposites. That is what I wrote except I said that the agonist, or the main muscle, is used for flexion, while the antagonist is used for extension. You noted that these were opposites and so did I.
One thing I left out in my response was about fixators. Basically, fixators are a type of synergist, that prevents movement at another joint. This allows for maximum movement of the main muscle. Basically at elbow flexion, the muscles of the scapula help keep it still due to the fixators (Martini and Nath 2009 p. 340). This allows for flexion to be isolated to the elbow.
You mentioned two types of movement that I wasn't as familiar with: "Retraction- Movement at your arms to your shoulders". Here I picture a superman pose. Retrusion- is opposite of Protrusion, moving your part posteriorly, here I picture superman trying to fly in reverse.
I learned a lot just from reading your assignment.
Martini, R., Nath, J. (2009). Fundamentals of Anatomy and Physiology. (8th ed.). San Francisco, CA. Pearson Education Inc.
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