Hi, and welcome back to anatomy basics. It's good to see you here in lecture two of section two where you will learn about the muscles. I will start with showing you how muscles are built. And after that we get into the different ways of tightening. That means the way muscles contract to deliver the power you need. And in the end of this lecture, I will also tell you about how muscles are attached to the bones or to other tissue.
You see a muscle in this picture right? Now when you open up the outer membrane, you'll see several bundles and when you open up one bundle, you'll again see new smaller bundles. There is some magic going on when you look at muscles. They are constructed like a Russian Matryoshka doll, where you kind of see the same structure in a smaller version several times in a row. What it comes down to is that in And you will look at the contracting fibers. When a nerve impulse reaches a couple of fibers called a motor unit, these fibers will electrically be put to tighten or contract.
In doing so, the fiber scroll together and shorten the muscle while at the same time thickening the muscle belly. The shortening of the muscle causes that one end of the muscle moves towards the other. And because it attaches at a particular spot on the boom, this bone will move as well. That is when you see an elbow flexing or a finger extending. Now about this contracting of a muscle I have something more to tell you. So far we have been talking about concentric tightening where during tightening the muscle shortens But the muscle fibers can also contract where at the same time the muscle lengthens.
This is called eccentric tightening. Then we have a third way of tightening and that is called isokinetic. Tightening. That means your muscle is tight, but the joint is not moving therefore the muscle keeps at the same length. in daily life you change all the time, from concentric to eccentric to isokinetic moving, for instance, moving a heavy box. Lifting the box is concentric, walking it to the other room is isokinetic and putting it slowly down is eccentric.
In general, concentric tightening happens against gravity. And eccentric tightening is for slowing down the effect of gravity. muscles have a beginning and an end. They are called origin and insertion. Most of the time, the muscles have tendons on both sides, but it's not uncommon that a muscle starts directly from the bone without a tendon and muscles can also have their origin from fasciae or Oppo neuroses, which is called gene tissue. Here you see some examples.
Last but not least, I have to make another classification in muscles. nano articular by articular and melt articular muscles, a mono articular muscle only has one joint between its origin and insertion. So it's only possible to cause movement in this one joint with this muscle by articular muscle has two joints between origin and insertion and therefore it is able to cause movements over more than one joint. And then in the end, there are muscles that jump over even more joints than to affecting the joints to a greater or lesser extent. Again, you have completed another lecture of anatomy basics, so you know a lot more about muscles than you did before. Thank you for watching this video.
And I'm looking forward to see you in lecture three, where we will continue with the names of all kinds of movements in various directions.