On McLuhan

So I've just read Chapter 1 of McLuhan, twice. I'm going to gather my thoughts, but they may be convoluted, as its my first attempt at externalizing everything I've just read. Consider what I'm writing more like notes/summarization I would take for a class.

1. McLuhan says that any medium is an extension of ourselves. Is this because we created each medium, and the medium's origins is rooted in a rationalized idea that could only come from a human brain? Does it have to do with utility?

2. An actual medium is just a medium. The content inside that medium is its own medium.

3. The message is not what is being said (i.e. "BARACK OBAMA IS A MUSLIM" being flashed on the television screen), that would be the content. Rather, the message is the effects of what the medium does for humanity (i.e. telephone speeding up the time it takes to converse with someone.) Quote: "It is the medium that shapes and controls the scale and form of human association and action."