I will attempt to answer the first part, but I am not sure about the second.
It is not about little brains in our muscles, but it is about our brain. Our brains have a bunch of neurons, each of which has a bunch of little tentacles at the ends (called dendrites). Memory, and muscle memory, and memory recall all rely on physical connections in the brain between these neurons. When you practice something, you are basically making more connections and stronger connection between neurons. Muscle memory is essentially what happens when your brain has a strong neural pathway in the parts of the brain required to undergo whatever task you are doing.
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