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Lecture Notes

Here you can see a very stylized picture of the parts of the muscular system that allow us to move, and what I want you to notice is that the skeletal muscle is receiving a signal from the brain via a motor nerve, and that's because these muscles are voluntary muscles, meaning we are required to send a signal from the brain to activate the muscle. And this is very different from the muscles in your heart that we talked about during the last lesson that contract involuntarily, or without you even thinking about it. So that's a major difference between these muscles that we're talking about here and the cardiac muscles that we talked about in the last lesson. You should also notice in this picture that there's a tendon—in this case we're looking at the biceps tendon—that connects the biceps muscle to the bones of your lower arm. When the muscle contracts, the tendon exerts force on the bone and you get the bicep curl movement.