Process:  -Electrical signals in the brain travel through nerves to muscles -Two types of proteins exist in filaments in the muscles -The filaments move when the brain instructs them to -The motion of the filaments cause the muscle to shorten and contract -Opposing pairs of muscles exist in order to provide the necessary range of motion.
 Question: What is the effect of "the bodys muscles are able to move" on muscles are moved in expanding motion.?
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