Source: Images and Video Created by Amanda Soderlind
Welcome to this lesson on Types of Skeletal Muscle. Today, we're going to discuss the two types of skeletal muscle, which are fast skeletal muscle, also known as white skeletal muscle, and slow, or red, skeletal muscle. So we're going to discuss examples of which types of muscle fall into each of these categories and what the difference between fast and slow, or white and red, skeletal muscles are. So let's start by discussing red skeletal muscles.
So red skeletal muscles, as I mentioned, are also known as slow skeletal muscles. So these are types of skeletal muscles that can contract slowly for long periods of time. So examples of red skeletal muscles are muscles that you use on a very regular basis, muscles that help you to maintain your posture, muscles that allow you to walk, so the muscles of your legs. These are muscles that we're using daily and we use for long periods of time. So these muscles need to be able to sustain activity for long periods of time.
So the muscles of your leg we'll use as an example. So these types of muscles have fibers that have more myoglobin and more capillaries in them to allow for the sustained activity that they require. So myoglobin is a protein that binds to oxygen, and it's found in the fibers of red muscle cells.
So this myoglobin that's found in these cells has a red color to it, so that's what gives muscles its red color is because of this myoglobin. So it's this protein that binds to oxygen. And it also has more capillaries running to it. So we have more blood running to these muscles, delivering oxygen and taking away carbon dioxide as these muscles work. So red muscles, muscles that can sustain activity for long periods of time.
White skeletal muscles, or fast muscles on the other hand, can contract quickly for short periods of time. So an example of this would be the muscles in your hand. The muscles in your hand can contract quickly, but they can't sustain activity for a very long period of time.
If you are writing, for example, you can only write so long before your hand really starts to cramp up. So the reason for this-- the reason that they have this white appearance to them, is because they have fewer capillaries running to them and less myoglobin. So remember, myoglobin is what gives red muscles that red appearance; but because white skeletal muscles don't have as much myoglobin, they have a white appearance.
They're not as red. And again, they have fewer capillaries running to them, which means less blood is supplied to them as well. So this is why they can only contract for short periods of time.
White skeletal muscles also have fewer mitochondria in them, which is another reason that they can only contract for short periods of time. There's more mitochondria in your red skeletal muscles, which provides those muscles with more ATP and more energy to sustain those contractions. So red skeletal muscles are able to contract for longer periods of time, whereas white skeletal muscles can only contract for shorter periods of time. So this lesson has been an overview on the two types of skeletal muscle, red and white.
A protein that binds oxygen which is necessary for the production of ATP.
Also known as red skeletal muscle; a type of muscle that can contract slowly for long periods of time.
Also known as white skeletal muscle; a type of muscle that can contract quickly for a short period of time.